What nerves innervate the muscles of the eyeball. Download medical textbooks, lectures

Oculomotor apparatus- a complex sensorimotor mechanism, the physiological significance of which is determined by its two main functions: motor (motor) and sensory (sensitive).

The motor function of the oculomotor system ensures the guidance of both eyes, their visual axes and the central fossae of the retinas to the object of fixation; the sensory function ensures the merging of two monocular (right and left) images into a single visual image.

The innervation of the extraocular muscles by the cranial nerves determines the close connection between neurological and ocular pathologies, as a result of which an integrated approach to diagnosis is necessary.

The constant stimulus for adduction (to ensure orthophoria) caused by the divergence of the orbits explains the fact that the medial rectus muscle is the most powerful of the rectus extraocular muscles. The disappearance of the stimulus for convergence with the onset of amaurosis leads to a noticeable deviation of the blind eye towards the temple.

All rectus muscles and the superior oblique begin in the depths of the orbit on the common tendon ring (anulus tendineus communis), fixed to the sphenoid bone and periosteum around the optic canal and partially at the edges of the superior orbital fissure. This ring surrounds the optic nerve and ophthalmic artery. The muscle that lifts the upper eyelid (m. levator palpebrae superioris) also begins from the common tendon ring. It is located in the orbit above the superior rectus muscle of the eyeball, and ends in the thickness of the upper eyelid. The rectus muscles are directed along the corresponding walls of the orbit, on the sides of the optic nerve, forming a muscular funnel, pierce the vagina of the eyeball (vagina bulbi) and with short tendons are woven into the sclera in front of the equator, 5-8 mm away from the edge of the cornea. The rectus muscles rotate the eyeball around two mutually perpendicular axes: vertical and horizontal (transverse).

Movements of the eyeball are carried out with the help of six extraocular muscles: four straight - external and internal (m. rectus externum, m.rectus internum), upper and lower (m.rectus superior, m.rectus inferior) and two obliques - upper and lower ( m.obliguus superior, m.obliguus inferior).

Superior oblique muscle of the eye originates from the tendon ring between the superior and internal rectus muscles and goes anteriorly to the cartilaginous block located in the superior internal corner of the orbit at its edge. At the pulley, the muscle turns into a tendon and, passing through the pulley, turns posteriorly and outward. Located under the superior rectus muscle, it is attached to the sclera outward from the vertical meridian of the eye. Two-thirds of the entire length of the superior oblique muscle is between the apex of the orbit and the trochlea, and one-third is between the trochlea and its attachment to the eyeball. This part of the superior oblique muscle determines the direction of movement of the eyeball during its contraction.

Unlike the five muscles mentioned inferior oblique muscle of the eye begins at the lower inner edge of the orbit (in the area of ​​the entrance of the nasolacrimal canal), goes posteriorly outward between the orbital wall and the inferior rectus muscle towards the external rectus muscle and is fan-shaped attached under it to the sclera in the posteroexternal part of the eyeball, at the level of the horizontal meridian of the eye.

Numerous cords extend from the fascial membrane of the extraocular muscles and Tenon’s capsule to the orbital walls.

The fascial-muscular apparatus provides fixed position eyeball, gives smoothness to its movements.

Some elements of the anatomy of the extrinsic muscles of the eye

	Properties
Superior rectus muscle (m. rectus superior)	Start : Lockwood's superior orbital tendon (a fragment of the common tendon ring of Zinn) in close proximity to the perineural sheath of the optic nerve. Attachment : to the sclera 6.7 mm from the limbus at an angle to it and slightly medial to the vertical axis of rotation of the eyeball, which explains the variety of its functions. Functions : primary - supraduction (75% of muscle effort), secondary - incycloduction (16% of muscle effort), tertiary - adduction (9% of muscle effort). Blood supply: the superior (lateral) muscular branch of the ophthalmic artery, as well as the lacrimal, supraorbital and posterior ethmoidal arteries. Innervation: superior branch of the ipsilateral oculomotor nerve (n. III). Motor fibers penetrate this and almost all other muscles, usually at the border of its posterior and middle thirds. Anatomy details: Attached behind ora serrata. As a consequence, perforation of the sclera when applying a frenulum suture will lead to a retinal defect. Together with the levator palpebrae superioris muscle, it forms the superior muscle complex
Inferior rectus muscle (m. rectus inferior)	Start: inferior orbital tendon of Zinn (fragment of the common tendon ring of Zinn). Attachment: to the sclera 5.9 mm from the limbus at an angle to it and slightly medial to the vertical axis of rotation of the eyeball, which explains the variety of its functions. Function: primary - infraduction (73%), secondary - excycloduction (17%), tertiary - adduction (10%). Blood supply : inferior (medial) muscular branch of the ophthalmic artery, infraorbital artery. Innervation : inferior branch of the ipsilateral oculomotor nerve (n. III). Anatomy details : forms the lower muscle complex with the inferior oblique muscle
Lateral rectus muscle (m. rectus lateralis)	Start : main (medial) leg - the superior orbital tendon of Lockwood (a fragment of the common tendon ring of Zinn); non-permanent (lateral) leg - a bony protrusion (spina recti lateralis) in the middle of the lower edge of the superior orbital fissure. Attachment : to the sclera 6.3 mm from the limbus. Function : primary - abduction (99.9% of muscle effort). Blood supply : superior (lateral) muscular artery from the ophthalmic artery, lacrimal artery, sometimes infraorbital artery and inferior (medial) muscular branch of the ophthalmic artery. Innervation : ipsilateral abducens nerve (n.VI). Anatomy details : has the most powerful fixing ligament
Medial rectus muscle (m. rectus medialis)	Start : Lockwood's superior orbital tendon (a fragment of Zinn's tendon ring) in close proximity to the perineural sheath of the optic nerve. Attachment : to the sclera 5 mm from the limbus. Function: primary - adduction (99.9% of muscle effort). Blood supply : inferior (medial) muscular branch of the ophthalmic artery; posterior ethmoidal artery. Innervation: inferior branch of the ipsilateral oculomotor nerve (n. III). Anatomy details: most powerful oculomotor muscle
Inferior oblique muscle (m. obliquus inferior)	Start: periosteum of the flattened portion of the orbital surface upper jaw under the anterior lacrimal ridge at the opening of the nasolacrimal canal. Attachment : the posterior outer surface of the eyeball slightly behind the vertical axis of rotation of the eyeball. Function : primary - excycloduction (59%), secondary - supraduction (40%); tertiary - abduction (1%). Blood supply : inferior (medial) muscular branch of the ophthalmic artery, infraorbital artery, rarely - lacrimal artery. Innervation: the lower branch of the contralateral oculomotor nerve (n. III), running along the outer edge of the inferior rectus muscle and penetrating the inferior oblique muscle at the level of the equator of the eyeball, and not at the border of the posterior and middle third of the muscle, as happens with all other extraocular muscles. This 1–1.5 mm thick trunk (containing parasympathetic fibers innervating the pupillary sphincter) is often damaged during reconstruction of a fracture of the inferior wall of the orbit, leading to postoperative Adie syndrome. Anatomy details: the absence of a tendon explains the bleeding that occurs when the muscle is cut from the sclera
Superior oblique muscle (m. obliquus superior)	Start : periosteum of the body of the sphenoid bone above the superior rectus muscle. Attachment: sclera of the posterior superior quadrant of the eyeball. Function: primary - incycloduction (65%), secondary - infraduction (32%), tertiary - abduction (3%). Blood supply : superior (lateral) muscular artery from the ophthalmic artery, lacrimal artery, anterior and posterior ethmoidal arteries. Innervation: contralateral trochlear nerve (n. IV). Anatomy details: longest tendon (26 mm), pulley - functional origin of the muscle

All these nerves pass into the orbit through the superior orbital fissure.

The oculomotor nerve, after entering the orbit, divides into two branches. The superior branch innervates the superior rectus muscle and the levator palpebrae superioris, the inferior branch innervates the internal and inferior rectus muscles, as well as the inferior oblique.

The nucleus of the oculomotor nerve and the nucleus of the trochlear nerve located behind and next to it (provides the work of the oblique muscles) are located at the bottom of the aqueduct of Sylvius (aqueduct of the brain). The nucleus of the abducens nerve (provides the work of the external rectus muscle) is located in the pons under the bottom of the rhomboid fossa.

The rectus oculomotor muscles of the eye are attached to the sclera at a distance of 5-7 mm from the limbus, the oblique muscles - at a distance of 16-19 mm.

The width of the tendons at the muscle attachment site ranges from 6-7 to 8-10 mm. Of the rectus muscles, the widest tendon is the internal rectus muscle, which plays a major role in the function of bringing together the visual axes (convergence).

The line of attachment of the tendons of the internal and external muscles of the eye, i.e., their muscular plane, coincides with the plane of the horizontal meridian of the eye and is concentric with the limbus. This causes horizontal movements of the eyes, their adduction, rotation to the nose - adduction during contraction of the internal rectus muscle and abduction, rotation towards the temple - abduction during contraction of the external rectus muscle. Thus, these muscles are antagonistic in nature.

The superior and inferior rectus and oblique muscles of the eye perform mainly vertical movements of the eye. The line of attachment of the superior and inferior rectus muscles is located somewhat obliquely, their temporal end is further from the limbus than the nasal end. As a result, the muscular plane of these muscles does not coincide with the plane of the vertical meridian of the eye and forms an angle with it that is on average 20° and open to the temple.

This attachment ensures rotation of the eyeball under the action of these muscles, not only upward (during contraction of the superior rectus muscle) or downward (during contraction of the inferior rectus muscle), but simultaneously inwardly, i.e. adduction.

The oblique muscles form an angle of about 60° with the plane of the vertical meridian, open to the nose. This determines the complex mechanism of their action: the superior oblique muscle lowers the eye and produces its abduction (abduction), the inferior oblique muscle is an elevator and also an abductor.

In addition to horizontal and vertical movements, these four vertically acting oculomotor muscles of the eye perform torsional eye movements clockwise or counterclockwise. In this case, the upper end of the vertical meridian of the eye deviates towards the nose (intrusion) or towards the temple (extortion).

Thus, the extraocular muscles of the eye provide the following eye movements:

• adduction (adduction), i.e. its movement towards the nose; this function is performed by the internal rectus muscle, additionally by the superior and inferior rectus muscles; they are called adductors;
• abduction (abduction), i.e. movement of the eye towards the temple; this function is performed by the external rectus muscle, additionally by the superior and inferior oblique muscles; they are called abductors;
• upward movement - under the action of the superior rectus and inferior oblique muscles; they are called lifters;
• downward movement - under the action of the inferior rectus and superior oblique muscles; they are called lowerers.

The complex interactions of the extraocular muscles of the eye are manifested in the fact that when moving in some directions they act as synergists (for example, partial adductors - the superior and inferior rectus muscles, in others - as antagonists (superior rectus - levator, inferior rectus - depressor).

The extraocular muscles provide two types of conjugal movements of both eyes:

• unilateral movements (in the same direction - right, left, up, down) - so-called version movements;
• opposite movements (in different directions) - vergence, for example, to the nose - convergence (bringing together the visual axes) or to the temple - divergence (spreading the visual axes), when one eye turns to the right, the other to the left.

Vergence and version movements can also be performed in the vertical and oblique directions.

Muscle	Start	Attachment	Function	Innervation
External straight	Fibrous ring of Zinn	Lateral wall of the eyeball	Abduction of the eyeball laterally (outward)	Abducens nerve (VI pair of cranial nerves)
Inner straight	Fibrous ring of Zinn	Medial wall of the eyeball	Adduction of the eyeball medially (inward)
Bottom straight	Fibrous ring of Zinn	Inferior wall of the eyeball	Lowers the eyeball, slightly moves it outward	Oculomotor nerve (III pair of cranial nerves)
Top straight	Fibrous ring of Zinn		Raises the eyeball, slightly brings it inwards	Oculomotor nerve (III pair of cranial nerves)
Inferior oblique	Orbital surface of the maxilla	Inferior wall of the eyeball	Lifts, abducts and slightly rotates outward	Oculomotor nerve (III pair of cranial nerves)
Superior oblique	Ring of Zinn - block on the orbital surface of the frontal bone	Superior wall of the eyeball	Lowers, adducts and slightly rotates medially	Trochlear nerve (IV pair of cranial nerves)

The functions of the oculomotor muscles described above characterize the motor activity of the oculomotor apparatus, while the sensory one is manifested in the function of binocular vision.

Schematic representation of the movement of the eyeballs during contraction of the corresponding muscles:

■ Eye development

■ Eye socket

■ Eyeball

Outer shell

Middle shell

Inner layer (retina)

Contents of the eyeball

Blood supply

Innervation

Visual pathways

■ Auxiliary apparatus of the eye

Oculomotor muscles

Eyelids

Conjunctiva

Lacrimal organs

EYE DEVELOPMENT

The eye rudiment appears in the 22-day embryo as a pair of shallow invaginations (ocular grooves) in the forebrain. Gradually, the invaginations increase and form outgrowths - eye vesicles. At the beginning of the fifth week of fetal development, the distal part of the optic vesicle is depressed, forming the optic cup. The outer wall of the optic cup gives rise to the retinal pigment epithelium, and the inner wall gives rise to the remaining layers of the retina.

At the stage of the optic vesicles, thickenings appear in the adjacent areas of the ectoderm - lens placoids. Then the formation of lens vesicles occurs and they are drawn into the cavity of the optic cups, while the anterior and posterior chambers of the eye are formed. The ectoderm above the optic cup also gives rise to the corneal epithelium.

In the mesenchyme immediately surrounding the optic cup, the vascular network develops and the choroid is formed.

Neuroglial elements give rise to the myoneural tissue of the sphincter and pupillary dilator. Outward from choroid dense fibrous unformed tissue of the sclera develops from the mesenchyme. Anteriorly, it becomes transparent and passes into the connective tissue part of the cornea.

At the end of the second month, lacrimal glands develop from the ectoderm. The oculomotor muscles develop from myotomes, represented by the striated muscle tissue somatic type. The eyelids begin to form as folds of skin. They quickly grow towards each other and grow together. Behind them a space is formed, which is lined with stratified prismatic epithelium - the conjunctival sac. At the 7th month of intrauterine development, the conjunctival sac begins to open. Along the edge of the eyelids, eyelashes are formed, greasy and modified sweat glands.

Features of the structure of the eyes in children

In newborns, the eyeball is relatively large, but short. By the age of 7-8 years, the final eye size is established. A newborn has a relatively larger and flatter cornea than an adult. At birth, the shape of the lens is spherical; throughout life, it grows and becomes flatter, which is due to the formation of new fibers. In newborns, there is little or no pigment in the stroma of the iris. The bluish color of the eyes is given by the translucent posterior pigment epithelium. When pigment begins to appear in the parenchyma of the iris, it acquires its own color.

ORIENTAL

Orbit(orbita), or eye socket, - paired bone formation in the form of a depression in the front of the skull, resembling a tetrahedral pyramid, the apex of which is directed posteriorly and somewhat inward (Fig. 2.1). The orbit has inner, upper, outer and lower walls.

The inner wall of the orbit is represented by a very thin bone plate that separates the orbital cavity from the cells of the ethmoid bone. If this plate is damaged, air from the sinus can easily pass into the orbit and under the skin of the eyelids, causing emphysema. In the top-inside

Rice. 2.1.Orbital structure: 1 - superior orbital fissure; 2 - small wing of the main bone; 3 - optic nerve channel; 4 - posterior ethmoidal opening; 5 - orbital plate of the ethmoid bone; 6 - anterior lacrimal ridge; 7 - lacrimal bone and posterior lacrimal crest; 8 - fossa of the lacrimal sac; 9 - nasal bone; 10 - frontal process; 11 - lower orbital margin (upper jaw); 12 - lower jaw; 13 - inferior orbital groove; 14. infraorbital foramen; 15 - inferior orbital fissure; 16 - zygomatic bone; 17 - round hole; 18 - large wing of the main bone; 19 - frontal bone; 20 - upper orbital margin

In the lower angle, the orbit borders the frontal sinus, and the lower wall of the orbit separates its contents from the maxillary sinus (Fig. 2.2). This makes it likely that inflammatory and tumor processes will spread from the paranasal sinuses into the orbit.

The inferior wall of the orbit is often damaged by blunt trauma. A direct blow to the eyeball causes a sharp increase in pressure in the orbit, and its lower wall “falls in,” dragging the contents of the orbit into the edges of the bone defect.

Rice. 2.2.Orbit and paranasal sinuses: 1 - orbit; 2 - maxillary sinus; 3 - frontal sinus; 4 - nasal passages; 5 - ethmoid sinus

The tarso-orbital fascia and the eyeball suspended on it serve as the anterior wall delimiting the orbital cavity. The tarso-orbital fascia is attached to the orbital margins and cartilages of the eyelids and is closely associated with Tenon's capsule, which covers the eyeball from the limbus to the optic nerve. In front, Tenon's capsule is connected to the conjunctiva and episclera, and behind it separates the eyeball from the orbital tissue. Tenon's capsule forms the sheath for all extraocular muscles.

The main contents of the orbit are fatty tissue and extraocular muscles, the eyeball itself occupies only a fifth of the orbital volume. All formations located anterior to the tarso-orbital fascia lie outside the orbit (in particular, the lacrimal sac).

Connection of the orbit with the cranial cavity carried out through several holes.

The superior orbital fissure connects the orbital cavity with the middle cranial fossa. The following nerves pass through it: oculomotor (III pair of cranial nerves), trochlear (IV pair of cranial nerves), orbital (first branch of the V pair of cranial nerves) and abducens (VI pair of cranial nerves). The superior ophthalmic vein also passes through the superior orbital fissure, the main vessel through which blood flows from the eyeball and orbit.

Pathology in the area of ​​the superior orbital fissure can lead to the development of the “superior orbital fissure” syndrome: ptosis, complete immobility of the eyeball (ophthalmoplegia), mydriasis, paralysis of accommodation, impaired sensitivity of the eyeball, skin of the forehead and upper eyelid, difficulty in venous outflow of blood, which causes the occurrence of exophthalmos.

The orbital veins pass through the superior orbital fissure into the cranial cavity and empty into the cavernous sinus. Anastomoses with facial veins, primarily through the angular vein, as well as the absence of venous valves, contribute to the rapid spread of infection from the upper part of the face into the orbit and further into the cranial cavity with the development of cavernous sinus thrombosis.

The inferior orbital fissure connects the orbital cavity with the pterygopalatine and temporomandibular fossae. The inferior orbital fissure is closed by connective tissue into which smooth muscle fibers are woven. When the sympathetic innervation of this muscle is disrupted, enophthalmos occurs (recession of the eyes).

no apple). Thus, when the fibers running from the superior cervical sympathetic ganglion to the orbit are damaged, Horner's syndrome develops: partial ptosis, miosis and enophthalmos. The optic nerve canal is located at the apex of the orbit in the lesser wing of the sphenoid bone. Through this canal the optic nerve enters the cranial cavity and the ophthalmic artery enters the orbit - the main source of blood supply to the eye and its auxiliary apparatus.

EYEBALL

The eyeball consists of three membranes (outer, middle and inner) and contents (vitreous body, lens, and aqueous humor of the anterior and posterior chambers of the eye, Fig. 2.3).

Rice. 2.3.Diagram of the structure of the eyeball (sagittal section).

Outer shell

Outer, or fibrous, membrane of the eye (tunica fibrosa) represented by the cornea (cornea) and sclera (sclera).

Cornea - the transparent avascular part of the outer membrane of the eye. The function of the cornea is to conduct and refract light rays, as well as protect the contents of the eyeball from adverse external influences. The diameter of the cornea is on average 11.0 mm, thickness - from 0.5 mm (in the center) to 1.0 mm, refractive power - about 43.0 diopters. Normally, the cornea is transparent, smooth, shiny, spherical and highly sensitive tissue. The impact of unfavorable external factors on the cornea causes a reflexive contraction of the eyelids, providing protection to the eyeball (corneal reflex).

The cornea consists of 5 layers: anterior epithelium, Bowman's membrane, stroma, Descemet's membrane and posterior epithelium.

Front multilayered squamous non-keratinizing epithelium performs a protective function and, in case of injury, completely regenerates within 24 hours.

Bowman's membrane- basement membrane of the anterior epithelium. It is resistant to mechanical stress.

Stroma(parenchyma) cornea makes up up to 90% of its thickness. It consists of many thin plates, between which there are flattened cells and a large number of sensitive nerve endings.

"Descemet's membrane represents the basement membrane of the posterior epithelium. It serves as a reliable barrier to the spread of infection.

Posterior epithelium consists of a single layer of hexagonal cells. It prevents the flow of water from the anterior chamber moisture into the corneal stroma and does not regenerate.

The cornea is nourished by the pericorneal network of vessels, moisture from the anterior chamber of the eye and tears. The transparency of the cornea is due to its homogeneous structure, the absence of blood vessels and a strictly defined water content.

Limbo- the place of transition of the cornea into the sclera. This is a translucent rim, about 0.75-1.0 mm wide. Schlemm's canal is located in the thickness of the limbus. The limbus serves as a good guide when describing various pathological processes in the cornea and sclera, as well as when performing surgical interventions.

Sclera- the opaque part of the outer shell of the eye, which is white (the tunica albuginea). Its thickness reaches 1 mm, and the thinnest part of the sclera is located at the exit point of the optic nerve. The functions of the sclera are protective and formative. The sclera is similar in structure to the parenchyma of the cornea, however, unlike it, it is saturated with water (due to the absence of epithelial cover) and is opaque. Numerous nerves and vessels pass through the sclera.

Middle shell

The middle (choroid) layer of the eye, or uveal tract (tunica vasculosa), consists of three parts: the iris (iris), ciliary body (corpus ciliare) and choroids (choroidea).

Iris serves as the automatic diaphragm of the eye. The thickness of the iris is only 0.2-0.4 mm, the smallest is at the point of its transition to the ciliary body, where the iris can be torn off due to injury (iridodialysis). The iris consists of connective tissue stroma, blood vessels, epithelium covering the iris in front and two layers of pigment epithelium behind, ensuring its opacity. The stroma of the iris contains many chromatophore cells, the amount of melanin in which determines the color of the eyes. The iris contains a relatively small number of sensitive nerve endings, so inflammatory diseases of the iris are accompanied by moderate pain.

Pupil- a round hole in the center of the iris. By changing its diameter, the pupil regulates the flow of light rays falling on the retina. The size of the pupil changes under the action of two smooth muscles of the iris - the sphincter and the dilator. The sphincter muscle fibers are arranged in a ring and receive parasympathetic innervation from the oculomotor nerve. The radial dilator fibers are innervated from the superior cervical sympathetic ganglion.

Ciliary body- part of the choroid of the eye, which in the form of a ring passes between the root of the iris and the choroid. The border between the ciliary body and the choroid passes along the dentate line. The ciliary body produces intraocular fluid and participates in the act of accommodation. The vascular network is well developed in the area of ​​the ciliary processes. The formation of intraocular fluid occurs in the ciliary epithelium. Ciliary

the muscle consists of several bundles of multidirectional fibers attached to the sclera. By contracting and pulling anteriorly, they weaken the tension of the ligaments of Zinn, which go from the ciliary processes to the lens capsule. When the ciliary body is inflamed, the processes of accommodation are always disrupted. The innervation of the ciliary body is carried out by sensory (I branch of the trigeminal nerve), parasympathetic and sympathetic fibers. There are significantly more sensitive nerve fibers in the ciliary body than in the iris, so when it becomes inflamed pain syndrome sharply expressed. Choroid- the posterior part of the uveal tract, separated from the ciliary body by a dentate line. The choroid consists of several layers of vessels. A layer of wide choriocapillaris is adjacent to the retina and is separated from it by a thin Bruch membrane. On the outside there is a layer of medium-sized vessels (mainly arterioles), behind which there is a layer of larger vessels (venules). Between the sclera and the choroid there is a suprachoroidal space in which vessels and nerves pass in transit. Pigment cells are located in the choroid, as in other parts of the uveal tract. The choroid provides nutrition to the outer layers of the retina (neuroepithelium). Blood flow in the choroid is slow, which contributes to the occurrence of metastatic tumors and the settling of pathogens of various infectious diseases. The choroid does not receive sensitive innervation, so choroiditis is painless.

Inner layer (retina)

The inner layer of the eye is represented by the retina (retina) - highly differentiated nervous tissue designed to perceive light stimuli. From the optic disc to the dentate line is the optically active part of the retina, which consists of the neurosensory and pigment layers. Anterior to the dentate line, located 6-7 mm from the limbus, it is reduced to the epithelium covering the ciliary body and iris. This part of the retina is not involved in the act of vision.

The retina is fused to the choroid only along the dentate line anteriorly and around the optic disc and along the edge of the macula posteriorly. The thickness of the retina is about 0.4 mm, and in the area of ​​the dentate line and in the macula - only 0.07-0.08 mm. Retinal nutrition

carried out by the choroid and the central retinal artery. The retina, like the choroid, does not have pain innervation.

The functional center of the retina, the macula (macula), is an avascular, rounded area. yellow which is due to the presence of pigments lutein and zeaxanthin. The most photosensitive part of the macula is the fovea, or foveola (Fig. 2.4).

Retinal structure diagram

Rice. 2.4.Diagram of the structure of the retina. Topography of retinal nerve fibers

The first 3 neurons of the visual analyzer are located in the retina: photoreceptors (first neuron) - rods and cones, bipolar cells (second neuron) and ganglion cells (third neuron). Rods and cones represent the receptor part of the visual analyzer and are located in the outer layers of the retina, directly next to its pigment epithelium. Sticks, located on the periphery, are responsible for peripheral vision - field of view and light perception. cones, the bulk of which are concentrated in the area of ​​the macula, provide central vision (visual acuity) and color perception.

The high resolution of the macula is due to the following features.

The retinal vessels do not pass through here and do not prevent light rays from reaching the photoreceptors.

Only the cones are located in the fovea; all other layers of the retina are pushed to the periphery, which allows light rays to fall directly on the cones.

A special ratio of retinal neurons: in the central fovea there is one bipolar cell per cone, and for each bipolar cell there is its own ganglion cell. This ensures a “direct” connection between photoreceptors and visual centers.

In the periphery of the retina, on the contrary, several rods have one bipolar cell, and several bipolar cells have one ganglion cell. The summation of irritations provides the peripheral part of the retina with exceptionally high sensitivity to the minimum amount of light.

The axons of the ganglion cells converge to form the optic nerve. The optic disc corresponds to the point where nerve fibers exit the eyeball and does not contain light-sensitive elements.

Contents of the eyeball

Contents of the eyeball - vitreous humor (corpus vitreum), lens (lens), as well as aqueous humor of the anterior and posterior chambers of the eye (humor aquosus).

Vitreous body in weight and volume it is approximately 2/3 of the eyeball. This is a transparent avascular gelatinous formation that fills the space between the retina, ciliary body, fibers of the ligament of zinc and the lens. The vitreous body is separated from them by a thin limiting membrane, inside which there is a skeleton of

thin fibrils and gel-like substance. The vitreous body consists of more than 99% water, in which small amounts of protein, hyaluronic acid and electrolytes are dissolved. The vitreous body is quite firmly connected with the ciliary body, the lens capsule, as well as with the retina near the dentate line and in the area of ​​the optic nerve head. With age, the connection with the lens capsule weakens.

Lens(lens) - a transparent, avascular elastic formation, having the shape of a biconvex lens with a thickness of 4-5 mm and a diameter of 9-10 mm. The lens substance has a semi-solid consistency and is enclosed in a thin capsule. The functions of the lens are to conduct and refract light rays, as well as participate in accommodation. The refractive power of the lens is about 18-19 diopters, and at maximum accommodation voltage - up to 30-33 diopters.

The lens is located directly behind the iris and is suspended by fibers of the ligament of zinn, which are woven into the lens capsule at its equator. The equator divides the lens capsule into anterior and posterior. In addition, the lens has anterior and posterior poles.

Under the anterior capsule of the lens is a subcapsular epithelium that produces fibers throughout life. At the same time, the lens becomes flatter and denser, losing its elasticity. The ability to accommodate is gradually lost, since the compacted substance of the lens cannot change its shape. The lens consists of almost 65% water, and the protein content reaches 35% - more than in any other tissue of our body. The lens also contains very small amounts of minerals, ascorbic acid and glutathione.

Intraocular fluid produced in the ciliary body, fills the anterior and posterior chambers of the eye.

The anterior chamber of the eye is the space between the cornea, iris and lens.

The posterior chamber of the eye is a narrow gap between the iris and the lens with the ligament of zinn.

Aqueous moisture participates in the nutrition of the avascular media of the eye, and its exchange largely determines the value of intraocular pressure. The main pathway for the outflow of intraocular fluid is the angle of the anterior chamber of the eye, formed by the root of the iris and the cornea. Through the trabecular system and the layer of internal epithelial cells, the fluid enters Schlemm's canal (venous sinus), from where it flows into the veins of the sclera.

Blood supply

All arterial blood enters the eyeball through the ophthalmic artery (a. ophthalmica)- branches of the internal carotid artery. The ophthalmic artery gives off the following branches going to the eyeball:

The central retinal artery, which supplies the inner layers of the retina;

Posterior short ciliary arteries (6-12 in number), dichotomously branching in the choroid and supplying it with blood;

Posterior long ciliary arteries (2), which pass in the suprachoroidal space to the ciliary body;

The anterior ciliary arteries (4-6) arise from the muscular branches of the ophthalmic artery.

The posterior long and anterior ciliary arteries, anastomosing with each other, form the large arterial circle of the iris. Vessels extend from it in a radial direction, forming a small arterial circle of the iris around the pupil. Due to the posterior long and anterior ciliary arteries, the iris and ciliary body are supplied with blood, a pericorneal network of vessels is formed, which is involved in the nutrition of the cornea. A single blood supply creates the preconditions for simultaneous inflammation of the iris and ciliary body, while choroiditis usually occurs in isolation.

The outflow of blood from the eyeball is carried out through the vortex (whirlpool) veins, anterior ciliary veins and the central retinal vein. Vorticose veins collect blood from the uveal tract and leave the eyeball, obliquely piercing the sclera near the equator of the eye. The anterior ciliary veins and the central retinal vein drain blood from the basins of the arteries of the same name.

Innervation

The eyeball has sensitive, sympathetic and parasympathetic innervation.

Sensory innervation is provided by the ophthalmic nerve (I branch of the trigeminal nerve), which gives off 3 branches in the orbital cavity:

Lacrimal and supraorbital nerves, which are not related to the innervation of the eyeball;

The nasociliary nerve gives off 3-4 long ciliary nerves, which pass directly into the eyeball, and also takes part in the formation of the ciliary ganglion.

Ciliary nodelocated 7-10 mm from the posterior pole of the eyeball and adjacent to the optic nerve. The ciliary ganglion has three roots:

Sensitive (from the nasociliary nerve);

Parasympathetic (fibers go along with the oculomotor nerve);

Sympathetic (from fibers of the cervical sympathetic plexus). 4-6 short lines extend from the ciliary ganglion to the eyeball

ciliary nerves. They are joined by sympathetic fibers going to the pupillary dilator (they do not enter the ciliary ganglion). Thus, the short ciliary nerves are mixed, in contrast to the long ciliary nerves, which carry only sensory fibers.

The short and long ciliary nerves approach the posterior pole of the eye, pierce the sclera and run in the suprachoroidal space to the ciliary body. Here they give off sensory branches to the iris, cornea and ciliary body. The unity of innervation of these parts of the eye determines the formation of a single symptom complex - corneal syndrome (lacrimation, photophobia and blepharospasm) when any of them is damaged. Sympathetic and parasympathetic branches also extend from the long ciliary nerves to the muscles of the pupil and ciliary body.

Visual pathways

Visual pathwaysconsist of optic nerves, optic chiasm, optic tracts, as well as subcortical and cortical visual centers (Fig. 2.5).

Optic nerve (n. opticus, II pair of cranial nerves) is formed from the axons of ganglion neurons of the retina. In the fundus of the eye, the optic disc is only 1.5 mm in diameter and causes a physiological scotoma - a blind spot. Leaving the eyeball, the optic nerve receives the meninges and exits the orbit into the cranial cavity through the optic nerve canal.

Optic chiasm (chiasm) is formed at the intersection of the inner halves of the optic nerves. In this case, visual tracts are formed, which contain fibers from the outer parts of the retina of the same eye and fibers coming from the inner half of the retina of the opposite eye.

Subcortical visual centers located in the external geniculate bodies, where the axons of ganglion cells end. Fibers

Rice. 2.5.Diagram of the structure of the visual pathways, optic nerve and retina

the central neuron through the posterior thigh of the internal capsule and the Graziole bundle go to the cells of the cortex of the occipital lobe in the area of ​​the calcarine sulcus (cortical part of the visual analyzer).

AUXILIARY DEVICE OF THE EYE

The auxiliary apparatus of the eye includes the extraocular muscles, lacrimal organs (Fig. 2.6), as well as the eyelids and conjunctiva.

Rice. 2.6.The structure of the lacrimal organs and muscular apparatus of the eyeball

Oculomotor muscles

The extraocular muscles provide mobility to the eyeball. There are six of them: four straight and two oblique.

The rectus muscles (superior, inferior, external and internal) begin from the tendon ring of Zinn, located at the apex of the orbit around the optic nerve, and are attached to the sclera 5-8 mm from the limbus.

The superior oblique muscle starts from the periosteum of the orbit above and inward from the optic foramen, goes anteriorly, spreads over the block and, going somewhat posteriorly and downward, attaches to the sclera in the upper-outer quadrant 16 mm from the limbus.

The inferior oblique muscle originates from the medial wall of the orbit behind the inferior orbital fissure and attaches to the sclera in the inferior outer quadrant, 16 mm from the limbus.

The external rectus muscle, which abducts the eye outward, is innervated by the abducens nerve (VI pair of cranial nerves). The superior oblique muscle, the tendon of which is thrown over the block, is the trochlear nerve (IV pair of cranial nerves). The superior, internal and inferior rectus muscles, as well as the inferior oblique muscles, are innervated by the oculomotor nerve (III pair of cranial nerves). The blood supply to the extraocular muscles is carried out by the muscular branches of the ophthalmic artery.

Action of the extraocular muscles: the internal and external rectus muscles rotate the eyeball in a horizontal direction to the sides of the same name. The upper and lower straight lines are in the vertical direction to the sides of the same name and inward. The superior and inferior oblique muscles turn the eye in the direction opposite to the name of the muscle (i.e., superior - downward, and inferior - upward), and outward. The coordinated actions of six pairs of extraocular muscles provide binocular vision. In case of dysfunction of the muscles (for example, with paresis or paralysis of one of them), double vision occurs or the visual function of one of the eyes is suppressed.

Eyelids

Eyelids- movable skin-muscular folds covering the eyeball from the outside. They protect the eye from damage, excess light, and blinking helps to evenly cover the tear film

cornea and conjunctiva, protecting them from drying out. The eyelids consist of two layers: anterior - musculocutaneous and posterior - mucocartilaginous.

Cartilages of the eyelids- dense semilunar fibrous plates that give shape to the eyelids are connected to each other at the inner and outer corners of the eye by tendon adhesions. On the free edge of the eyelid, two ribs are distinguished - anterior and posterior. The space between them is called intermarginal, its width is approximately 2 mm. The ducts of the meibomian glands, located in the thickness of the cartilage, open into this space. At the front edge of the eyelids there are eyelashes, at the roots of which are the sebaceous glands of Zeiss and modified sweat glands of Moll. At the medial canthus, on the posterior edge of the eyelids, there are lacrimal puncta.

Skin of the eyelidsvery thin, subcutaneous tissue loose and does not contain adipose tissue. This explains the easy occurrence of eyelid edema in various local diseases and systemic pathologies (cardiovascular, renal, etc.). When the bones of the orbit, which form the walls of the paranasal sinuses, are fractured, air can get under the skin of the eyelids with the development of emphysema.

Eyelid muscles.The orbicularis oculi muscle is located in the tissues of the eyelids. When it contracts, the eyelids close. The muscle is innervated by the facial nerve, when damaged, lagophthalmos (non-closure of the palpebral fissure) and ectropion of the lower eyelid develop. In the thickness of the upper eyelid there is also a muscle that lifts the upper eyelid. It begins at the apex of the orbit and in three portions is woven into the skin of the eyelid, its cartilage and conjunctiva. The middle part of the muscle is innervated by fibers from the cervical part of the sympathetic trunk. Therefore, when sympathetic innervation is disrupted, partial ptosis occurs (one of the manifestations of Horner's syndrome). The remaining parts of the levator palpebrae superioris muscle receive innervation from the oculomotor nerve.

Blood supply to the eyelids carried out by branches of the ophthalmic artery. The eyelids have very good vascularization, due to which their tissues have a high reparative capacity. Lymphatic drainage from the upper eyelid is carried out into the pre-auricular lymph nodes, and from the lower - into the submandibular ones. Sensitive innervation of the eyelids is provided by the I and II branches of the trigeminal nerve.

Conjunctiva

ConjunctivaIt is a thin transparent membrane covered with multilayered epithelium. The conjunctiva of the eyeball (covers its anterior surface with the exception of the cornea), the conjunctiva of the transitional folds and the conjunctiva of the eyelids (covers its posterior surface) are distinguished.

Subepithelial tissue in the area of ​​transitional folds contains a significant amount of adenoid elements and lymphoid cells that form follicles. Other parts of the conjunctiva normally do not have follicles. In the superior conjunctiva transitional fold the accessory lacrimal glands of Krause are located and the ducts of the main lacrimal gland open. The stratified columnar epithelium of the conjunctiva of the eyelids secretes mucin, which, as part of the tear film, covers the cornea and conjunctiva.

The blood supply to the conjunctiva comes from the system of the anterior ciliary arteries and arterial vessels of the eyelids. Lymphatic drainage from the conjunctiva is carried out to the preauricular and submandibular lymph nodes. Sensitive innervation of the conjunctiva is provided by the I and II branches of the trigeminal nerve.

Lacrimal organs

The lacrimal organs include the tear-producing apparatus and lacrimal ducts.

Tear-producing apparatus (Fig. 2.7). The main lacrimal gland is located in the lacrimal fossa in the superior outer part of the orbit. The ducts (about 10) of the main lacrimal gland and many small accessory lacrimal glands of Krause and Wolfring exit into the upper conjunctival fornix. Under normal conditions, the function of the accessory lacrimal glands is sufficient to moisturize the eyeball. The lacrimal gland (main) begins to function under unfavorable external influences and some emotional states, which is manifested by lacrimation. The blood supply to the lacrimal gland is carried out from the lacrimal artery, the outflow of blood occurs into the veins of the orbit. Lymphatic vessels from the lacrimal gland they go to the pre-auricular lymph nodes. The lacrimal gland is innervated by the first branch of the trigeminal nerve, as well as by sympathetic nerve fibers from the superior cervical sympathetic ganglion.

Lacrimal ducts. Due to the blinking movements of the eyelids, the tear fluid entering the conjunctival fornix is ​​evenly distributed over the surface of the eyeball. The tear then collects in the narrow space between the lower eyelid and the eyeball - the tear stream, from where it goes to the tear lake in the medial corner of the eye. The upper and lower lacrimal openings, located on the medial part of the free edges of the eyelids, are immersed in the lacrimal lake. From the lacrimal openings, tears enter the superior and inferior lacrimal canaliculi, which empty into the lacrimal sac. The lacrimal sac is located outside the orbital cavity at its internal angle in the bony fossa. Next, the tear enters the nasolacrimal duct, which opens into the lower nasal passage.

A tear. Tear fluid consists mainly of water, and also contains proteins (including immunoglobulins), lysozyme, glucose, K+, Na+ and Cl - ions and other components. The normal pH of tears averages 7.35. Tears participate in the formation of the tear film, which protects the surface of the eyeball from drying out and becoming infected. The tear film is 7-10 microns thick and consists of three layers. Superficial - layer of lipids of the secretion of the meibomian glands. It slows down the evaporation of tear fluid. The middle layer is the tear fluid itself. The inner layer contains mucin produced by goblet cells of the conjunctiva.

Rice. 2.7.Tear-producing apparatus: 1 - Wolfring glands; 2 - lacrimal gland; 3 - Krause's gland; 4 - glands of Manz; 5 - crypts of Henle; 6 - excretory flow of the meibomian gland

The optic nerve (n. opticus, n. II) is divided into four parts:

• intraocular (pars intraocularis) 0.8 mm long,
• orbital (pars orbitalis) 24-25 mm long,
• channel (pars canalis), not exceeding 8-10 mm and, finally,
• intracranial (pars intracranialis) with a length of 10-16 mm.

Contains an average of 1.5 million axons. The diameter of the nerve in the area of ​​the optic nerve head (OND) is 1.5 mm; directly behind the optic disc, due to myelination of nerve fibers, the nerve thickens twice (up to 3.0 mm); in the orbital part its thickness reaches 4.5 mm, which is due to the appearance of perineural membranes.

Of great clinical importance is the difference between the length of the orbital part of the optic nerve (25 mm) and the distance from the posterior pole of the eye to the canalis opticus (18 mm). The S-shaped bend of the optic nerve, caused by a seven-millimeter “reserve,” ensures unhindered movement of the eyeball and also plays a vital damping role in case of injury.

III pair of cranial nerves

The oculomotor nerve (n. oculomotorius, n. III) consists of three components with clearly defined functions.

• Somatic efferent(motor) component innervates 4 of the 6 extraocular muscles and the muscle that lifts the upper eyelid, thereby playing a leading role in ensuring involuntary and voluntary eye movements.
• Visceral efferent(motor) component provides parasympathetic innervation to the muscle that constricts the pupil (pupillary reflex) and the ciliary muscle (accommodative function).
• , providing proprioceptive sensitivity of the innervated muscles. Has 24,000 axons.

Somatic efferent (motor) component starts from a complex of nuclei (two main lateral large cell nuclei, two additional small cell nuclei of Yakubovich-Edinger-Westphal and an additional small cell unpaired accommodative nucleus of Perlia), lying in the central gray matter of the midbrain tegmentum under the bottom of the Sylvian aqueduct at the level of the superior colliculus of the quadrigeminal.

On the coronal section of the trunk, the nuclei of the oculomotor nerve form the letter V, bounded on the inside by the Yakubovich-Edinger-Westphal nucleus and from below-laterally by the medial longitudinal fasciculus. The motor and visceral efferent fibers emerging from the nuclear complex are directed forward, in the ventral direction, carry out partial decussation and pass through the red nucleus.

After leaving the cerebral peduncles in the interpeduncular fossa, the oculomotor nerve passes next to the interpeduncular cistern, the tentorium of the cerebellum, between the posterior cerebral and superior cerebellar arteries.

Intracranial portion n. III is 25 mm. Perforating the dura mater, it penetrates the lateral wall of the cavernous sinus, where it is located above the trochlear nerve. It enters the orbit through the intraconal portion of the superior orbital fissure. Usually at the level of the wall of the cavernous sinus it is divided into superior and inferior branches.

The superior branch ascends outward from the optic nerve and innervates the levator palpebrae superioris and superior rectus muscles. The larger inferior ramus is divided into three branches - the external (parasympathetic root to the ciliary ganglion and fibers for the inferior oblique muscle), middle (inferior rectus) and internal (medial rectus muscle).

Thus, the oculomotor nerve innervates the following muscles:

• ipsilateral superior rectus muscle;
• muscle that lifts the upper eyelid, on both sides;
• ipsilateral medial rectus muscle;
• contralateral inferior oblique muscle;
• ipsilateral inferior rectus muscle.

Nuclei of the oculomotor nerve
1 - parasympathetic nucleus of Yakubovich-Edinger-Westphal (1` - Perlia nucleus),
2 - nucleus innervating the ipsilateral inferior rectus muscle,
3 - nucleus innervating the ipsilateral superior rectus muscle,
4 - centrally located unpaired caudal nucleus, innervating both muscles that lift the upper eyelid,
5 - nucleus of the contralateral inferior oblique muscle.
6 - nucleus of the ipsilateral medial rectus muscle,
7 - nucleus of the trochlear nerve, innervating the contralateral superior oblique muscle,
8 - nucleus of the abducens nerve, innervating the ipsilateral lateral rectus muscle.

Visceral efferent (motor) component begins in the accessory small-celled lateral nuclei of Yakubovich-Edinger-Westphal. Preganglionic parasympathetic fibers are directed ventrally through the midbrain, interpeduncular fossa, cavernous sinus, superior orbital fissure along with somatic motor fibers.

When passing through the wall of the cavernous sinus, parasympathetic fibers are diffusely dispersed, and after the oculomotor nerve exits the superior orbital fissure, they are grouped in its inferior branch (passing lateral to the inferior rectus muscle and entering the inferior oblique muscle posteriorly-inferiorly). From the lower branch, through the parasympathetic (oculomotor) root, the fibers enter the ciliary ganglion, where the second neuron of the pathway in question lies.

Postganglionic fibers leave the ciliary ganglion as part of 5-6 short ciliary nerves entering the posterior pole of the eye near the optic nerve, mainly on the temporal side. Next, the fibers go forward in the perichoroidal space and end in the ciliary muscle and the muscle that constricts the pupil, with 70-80 separate radial bundles, innervating them sectorally.

Somatic afferent fibers begin from the proprioceptors of the oculomotor muscles and pass as part of the branches of the oculomotor nerve to the cavernous sinus. In the wall of the latter, they enter the optic nerve through connecting branches and then reach the trigeminal ganglion, where the first neurons are located.

II neurons responsible for proprioceptive sensitivity are located in the midbrain nucleus of the V pair (in the midbrain tegmentum).

IV pair of cranial nerves

The nucleus of the trochlear nerve (n. IV) is located in the tegmentum of the midbrain at the level of the lower colliculi of the quadrigeminal in front of the central gray matter and ventral to the Sylvian aqueduct. Adjacent to the nucleus of the trochlear nerve is the complex of nuclei of the oculomotor nerve. Another adjacent structure is the myelinated medial longitudinal fasciculus.

The fibers leaving the nucleus are directed dorsally, bending around the midbrain aqueduct, decussate in the superior medullary velum and exit on the dorsal surface of the brainstem behind the contralateral inferior colliculus of the midbrain roof (plate quadrigeminal). Thus, the trochlear nerve is the only nerve whose fibers make a complete decussation and exit on the dorsal surface of the brain.

After exiting the brainstem into the enveloping (or quadrigeminal) cistern, the trochlear nerve bends around the cerebral peduncle from the lateral side and turns to the anterior surface of the trunk, located together with the oculomotor nerve between the posterior cerebral and superior cerebellar arteries. Then it enters the lateral wall of the cavernous sinus, where it is located near n. III, V 1, VI.

Due to the longest (~75 mm) intracranial part, the trochlear nerve is most often cranial nerves suffers from traumatic brain injury. It enters the orbit through the extraconal portion of the superior orbital fissure, superior to the outside relative to the common tendon ring of Zinn, which is why abduction and drooping of the eyeball can be observed after retrobulbar anesthesia.

In the orbit, the trochlear nerve courses medially between the superior muscle complex and the superior orbital wall and enters the proximal third of the superior oblique muscle. In addition to somatic efferent fibers, it also contains afferent fibers that provide proprioceptive sensitivity to the innervated muscle. The course of these fibers is similar to those located in n. III. Contains the smallest (1500) number of fibers.

VI pair of cranial nerves

The nucleus of the abducens nerve (n. VI) is located in the caudal part of the tegmentum of the pons, almost on the midline under the bottom of the fourth ventricle (rhomboid fossa) at the level of the facial tubercle, inward and dorsal to the nucleus facial nerve.

The root fibers of the nerve are directed forward, overcome the entire thickness of the pons and exit onto the lower (ventral) surface of the brain in the groove between the pons and the pyramid medulla oblongata. Next, the abducens nerve on the side of the basilar artery rises up along the anterior surface of the pons to the petrous part temporal bone, where, together with the inferior petrosal sinus, it appears under the ossified petrosphenoidal ligament of Gruber (ligamentum petrosphenoidale), which forms the Dorello canal with the apex of the pyramid of the temporal bone.

Next, the nerve makes a sharp turn forward, pierces the dura mater and enters the cavernous sinus, lying lateral to the internal carotid artery. The abducens nerve is the only nerve fused not with the wall of the cavernous sinus, but with the siphon of the internal carotid artery.

After leaving the sinus, the nerve enters the orbit through the intraconal portion of the superior orbital fissure, located under the oculomotor nerve, and approaches the lateral rectus muscle. Due to the long intracranial part and its location in the narrow bony canal of Dorello, the abducens nerve is often affected by cerebral head injury.

V pair of cranial nerves

The trigeminal nerve (n. trigeminus, n. V) is the largest cranial nerve. Consists of sensitive (radix sensoria) and motor (radix motoria) components.

• Sensitive part provides tactile, temperature and pain innervation to the fronto-parietal area of ​​the scalp, eyelids, facial skin, mucous membranes of the nose and oral cavity, teeth, eyeball, lacrimal gland, oculomotor muscles, etc.
• Motor part b provides innervation masticatory muscles. Motor fibers are contained only in the mandibular nerve, which is a mixed nerve. It also provides proprioceptive sensitivity of the masticatory muscles.

Trigeminal ganglion and trigeminal nerve complex

The trigeminal (lunate, Gasserian) node (gangl. trigeminale) provides sensitive innervation of the face. Located in the trigeminal cavity (cavum trigeminale, s. Meckel), formed by the sheets of the dura mater, located on the impression of the same name (impressio trigeminalis) of the apex of the pyramid of the temporal bone.

The relatively large (15-18 mm) trigeminal ganglion is concave posteriorly and convex anteriorly. Three main branches of the trigeminal nerve arise from its anterior convex edge:

• ophthalmic (V 1) - leaves the cranial cavity through the superior orbital fissure,
• maxillary (V 2) - leaves the cranial cavity through the round hole,
• mandibular (V 3) nerve - leaves the cranial cavity through the foramen ovale.

The motor root goes around the trigeminal ganglion from the inside, goes to the foramen ovale, where it joins the third branch of the trigeminal nerve, turning it into a mixed nerve.

The trigeminal ganglion contains pseudounipolar cells, the peripheral processes of which end in receptors that provide touch, pressure, discrimination, temperature and pain sensitivity. The central processes of the cells of the trigeminal ganglion enter the pons at the origin of the last middle cerebellar peduncle and end in the pontine (main sensory) nucleus of the trigeminal nerve (tactile and discriminatory sensitivity), the nucleus of the spinal tract of the trigeminal nerve (pain and temperature sensitivity) and the nucleus of the midbrain tract trigeminal nerve (proprioceptive sensitivity).

Mostovoe(nucl. pontinus n. trigemini), or main sensitive core, is located in the dorsolateral part of the upper part of the pons, lateral to the motor nucleus. The axons of the second, i.e., neurons that form this nucleus, move to the opposite side and, as part of the contralateral medial loop, rise to the ventrolateral nucleus of the thalamus.

Fibers of tactile sensitivity are involved in the formation of the arc of the corneal reflex. Impulses from the mucous membrane of the eye along the optic nerve reach the pontine nucleus of the trigeminal nerve (afferent part of the arch). Then, through the cells of the reticular formation, the impulses switch to the nucleus of the facial nerve and along its axons reach the orbicularis oculi muscle, ensuring the reflex closure of both eyes when one of them is touched (the efferent part of the arch).

Nucleus of the spinal tract(nucl. spinalis n. trigemini) is a downward continuation of the main sensory nucleus throughout the medulla oblongata up to the gelatinous substance (substantia gelatinosa) of the dorsal horns cervical region spinal cord(C 4). Provides pain and temperature sensitivity. Afferent fibers to this nucleus enter the spinal tract of the trigeminal nerve.

The fibers enter the caudal part (pars caudalis) of the spinal tract nucleus of the trigeminal nerve in a strict somatotopic order, located in the form of an inverted projection of the face and head. Pain sensitivity fibers included in optic nerve(V 1), end most caudally, followed by the fibers of the maxillary nerve (V 2), and finally, the most rostral (cranial) fibers are located as part of the mandibular nerve (V 3).

The spinal tract of the trigeminal nerve is joined by nociceptive fibers from the VII, IX and X pairs of cranial nerves (external ear, posterior third of the tongue, larynx and pharynx). The middle part (pars interpolaris) of the nucleus of the spinal tract receives pain afferentation from the dental pulp. Perhaps the middle and rostral (pars rostralis) parts are also responsible for the perception of pressure and touch.

Axons of second neurons, emerging from the nucleus of the spinal tract, pass to the opposite side in the form of a wide fan-shaped bundle, which, passing through the pons and midbrain to the thalamus, ends in its ventrolateral nucleus.

Axons of the third(thalamic) neurons pass in the posterior leg of the internal capsule to the caudal part of the postcentral gyrus, where the projection center of general sensitivity for the head region is located. The continuation of the pontine nucleus upward is the nucleus of the midbrain tract of the trigeminal nerve (nucl. mesencephalicus n. trigemini). Located lateral to the aqueduct, it is responsible for proprioceptive sensitivity, which comes from baroreceptors and muscle spindle receptors of the masticatory, facial and oculomotor muscles.

Motor, or chewable, core(nucl. motorius n. trigemini s. nucl. masticatorius) is located in the lateral part of the bridge tire, medial to the sensitive one. It receives impulses from both hemispheres, the reticular formation, the red nuclei, the roof of the midbrain, the medial longitudinal fasciculus, the midbrain nucleus, with which the motor nucleus is united by a monosynaptic reflex arc. The axons of the motor nucleus form the motor root, which goes to

• masticatory (lateral and medial pterygoid, masseter, temporal) muscles;
• tensor tympani muscle;
• muscle that strains the velum palatine;
• mylohyoid muscle;
• anterior belly of the digastric muscle.

Optic nerve (V 1) lies in the wall of the cavernous sinus lateral to the internal carotid artery, between the oculomotor and trochlear nerves. It enters the orbit through the superior orbital fissure, in the lumen of which it is divided into three branches (frontal, lacrimal and nasociliary), providing sensitive innervation to the orbit and the upper third of the face.

• The frontal nerve is the largest, located in the orbit between the muscle that lifts the upper eyelid and the periosteum of the upper wall of the orbit, innervates the inner half of the upper eyelid and the corresponding parts of the conjunctiva, forehead, scalp, frontal sinuses and half of the nasal cavity. It leaves the orbit in the form of terminal branches - the supraorbital and supratrochlear nerves.
• The lacrimal nerve is the thinnest, lying along top edge The lateral rectus muscle provides sensitive innervation to the conjunctiva and skin in the area of ​​the lacrimal gland. In addition, it contains postganglionic parasympathetic fibers, which provide reflex lacrimation.
• The nasociliary nerve is the only branch of the ophthalmic nerve that enters the orbit through the intraconal portion of the superior orbital fissure. Gives off a small branch that forms the sensitive root of the ciliary ganglion. These fibers pass through the ciliary ganglion in transit without participating in synaptic transmission, since they are peripheral processes of pseudounipolar cells of the trigeminal ganglion. They leave the ciliary ganglion in the form of 5-12 short ciliary nerves, providing sensory innervation to the cornea, iris and ciliary body. These nerves also contain sympathetic vasomotor fibers from the superior cervical ganglion. The nasociliary nerve gives off a number of branches: two long ciliary nerves; anterior and posterior (Luschka nerve) ethmoid nerves (innervation of the nasal mucosa, sphenoid sinus and posterior cells of the ethmoid bone); subtrochlear nerve (innervation of the lacrimal canaliculi, medial ligament of the eyelids, as well as the tip of the nose, which explains the origin of Hutchinson’s symptom (1866) - a rash of vesicles on the wings or tip of the nose with herpes zoster).

As already mentioned, maxillary nerve (V 2) , although it is adjacent to the wall of the cavernous sinus, it still does not lie between the leaves of the forming sinus outer wall dura mater. At the exit from the round foramen, the maxillary nerve gives off a large (up to 4.5 mm thick) branch - the infraorbital nerve (n. infraorbitalis). Together with the artery of the same name (a. infraorbitalis - branch of a. maxillaris), it enters the orbit through the inferior orbital fissure (in its center), lying under the periosteum.

Next, the nerve and artery lie on the lower wall of the orbit in the groove of the same name (sulcus infraorbitalis), which anteriorly turns into a canal 7-15 mm long, running in the thickness of the orbital surface of the body of the upper jaw almost parallel to the medial wall of the orbit. The canal opens on the face in the area of ​​the canine fossa with the infraorbital foramen (foramen infraorbitale), round in shape, with a diameter of 4.4 mm. In adults, it is located 4-12 mm below the middle of the infraorbital margin (average 9 mm).

It should be noted that, contrary to popular belief, the supra- and infraorbital foramina are not located on the same vertical, called the Hirtle line. In more than 70% of observations, the distance between the infraorbital foramina exceeds by 0.5-1 cm the distance between the supraorbital notches. The opposite situation is typical for those cases when, instead of the supraorbital notch, a foramen of the same name is formed. The vertical distance between the supraorbital notch and the infraorbital foramen averages 44 mm.

From the infratemporal fossa, through the inferior orbital fissure, the zygomatic nerve (n. zygomaticus) also enters the orbit, perforating its periosteum, where it immediately divides into two branches: zygomaticofacialis (r. zygomatico-facialis) and zygomaticotemporal (r. zygomatico-temporalis) ; both nerve trunks enter the canals of the same name in the zygomatic bone to pass to the skin of the zygomatic and temporal regions.

The previously mentioned important anastomosis to the lacrimal nerve, containing postganglionic parasympathetic fibers coming from the pterygopalatine ganglion, departs from the zygomaticotemporal branch in the orbit.

VII pair of cranial nerves

The facial nerve (n. facialis, n. VII) consists of three components, each of which is responsible for a specific type of innervation:

• motor efferent innervation of facial muscles originating from the second branchial arch: posterior belly of the digastric, stylohyoid and stapedius muscles, subcutaneous muscle of the neck;
• secretory efferent (parasympathetic) innervation of the lacrimal, submandibular and sublingual glands, glands of the mucous membrane of the nasopharynx, hard and soft palate;
• gustatory (special afferent) innervation: taste buds of the anterior two-thirds of the tongue, hard and soft palate.

Motor fibers make up the main part of the facial nerve, secretory and gustatory fibers are separated from the motor fibers by an independent sheath and form the intermediate nerve (Wrisberg, Sapolini, n. intermedius). According to the International Anatomical Nomenclature, the intermediate nerve is an integral part of the facial nerve (n. VII).

The motor nucleus of the facial nerve is localized in the ventrolateral part of the tegmentum of the pons on the border with the medulla oblongata. The fibers emerging from the nucleus are first directed medially and dorsally, bending around the nucleus of the abducens nerve (the internal genu of the facial nerve) in the form of a loop. They form the facial colliculus, colliculus facialis, at the bottom of the fourth ventricle, then move ventro-laterally to the caudal part of the pons and emerge on the ventral surface of the brain at the cerebellopontine angle.

The nerve root is located next to the root of the VIII pair (vestibular-cochlear nerve), above and lateral to the olive of the medulla oblongata, containing fibers of the intermediate nerve. The facial nerve then enters the internal ear canal and then into the facial nerve canal (fallopian canal of the petrous part of the temporal bone). At the bend of the canal there is a cranked unit (gangl. geniculi).

At the level of the geniculate ganglion, two portions of the facial nerve are separated. The motor fibers pass in transit through the geniculate ganglion, then turn at a right angle posterolaterally, are directed downward and exit the pyramid of the temporal bone through the stylomastoid foramen. After leaving the canal, the facial nerve gives off branches to the stylohyoid muscle and the posterior belly of the digastric muscle, and then forms a plexus in the thickness of the parotid gland.

The innervation of voluntary movements of the facial muscles is carried out by the branches of the parotid plexus:

• temporal branches (rr. temporales) - posterior, middle and anterior. They innervate the superior and anterior auricular muscles, the frontal belly of the supracranial muscle, the upper half of the orbicularis oculi muscle and the corrugator muscle;
• 2-3 zygomatic branches (rr. zygomatici), directed forward and upward, approaching the zygomatic muscles and the lower half of the orbicularis oculi muscle (which must be taken into account when performing akinesia according to Nadbath, O’Brien, van Lindt);
• 3-4 rather powerful buccal branches (rr. buccales) depart from the upper main branch of the facial nerve and send their branches to the zygomaticus major muscle, the laughter muscle, the buccal muscle, the muscles that elevate and depress the angle of the mouth, the orbicularis oris muscle and the nasal muscle;
• marginal branch of the mandible (r. marginalis mandibulae) - innervates the muscles that lower the angle of the mouth and the lower lip, as well as the mental muscle;
• The cervical branch (r. colli) in the form of 2-3 nerves approaches the subcutaneous muscle of the neck.

Thus, the facial nerve innervates the protractors (muscles that close the palpebral fissure) - m. orbicularis oculi, m. procerus, m. corrugator supercilii and one eyelid retractor - m. frontalis. Regulation of voluntary movements of the facial muscles is carried out by the motor cortex (precentral gyrus, gyrus praecentralis) through the corticonuclear tract, which runs in the posterior limb of the internal capsule and reaches both the ipsi- and contralateral motor nuclei of the facial nerve.

The part of the nucleus innervating the superior facial muscles receives ipsilateral and contralateral innervation. The portion of the nucleus innervating the inferior facial muscles receives corticonuclear fibers only from the contralateral motor cortex. This fact is of great clinical importance, since the central and peripheral paralysis facial nerve is accompanied by a different clinical picture.

Topical diagnosis of peripheral facial paralysis (Erb scheme)

Level of nerve damage	Symptom complex
Below the origin of the chorda tympani in the facial nerve canal	Paralysis of the ipsilateral facial muscles; ipsilateral sweating disorder
Above the origin of the chorda tympani and below the stapedius nerve (n. stapedius)	The same + impaired taste sensitivity on the anterior 2/3 of the ipsilateral half of the tongue; decreased salivation by the glands of the affected side
Above the origin of n. stapedius and below the origin of the greater petrosal nerve	Same + hearing loss
Above the origin of the greater petrosal nerve, the region of the geniculate ganglion	The same + decrease in reflex lacrimation; dryness of the ipsilateral half of the nasopharynx; possible vestibular disorders
Above the geniculate ganglion in the internal auditory canal	The same + disappearance of reflexive and affective (crying) lacrimation, hearing impairment in the hyperacusis variant
Internal auditory opening	Peripheral muscle paralysis, decreased or loss of hearing, decreased excitability of the vestibular apparatus; ipsilateral inhibition of tear and saliva production, absence of corneal and superciliary reflexes, taste disturbance with intact general sensitivity of the tongue (V3)

Unilateral interruption of the corticonuclear pathway leaves the innervation of the frontalis muscle intact (central palsy). A lesion at the level of the nucleus, root or peripheral nerve causes paralysis of all facial muscles of the ipsilateral half of the face - peripheral Bell's palsy.

Peripheral Paralysis Clinic:

• pronounced facial asymmetry;
• atrophy of the facial muscles;
• drooping eyebrow;
• smoothness of the frontal and nasolabial folds;
• drooping corner of the mouth;
• lacrimation;
• lagophthalmos;
• inability to close lips tightly;
• loss of food from the mouth when chewing on the affected side.

The combination of Bell's palsy with dysfunction of the abducens nerve indicates the localization of the pathological focus in the brain stem, with pathology of the vestibulocochlear nerve indicating the presence of a focus in the internal auditory canal.

Central facial palsy occurs as a result of damage to motor cortex neurons or their axons in the corticonuclear tract,located in the posterior leg of the internal capsule and ending in the motor nucleus of the facial nerve. As a result, voluntary contractions of the lower muscles of the contralateral side of the face suffer.Voluntary movements of the muscles of the upper half of the face are preserved due to their bilateral innervation.

Central Paralysis Clinic:

• facial asymmetry;
• atrophy of the muscles of the lower half of the face on the side opposite to the lesion (as opposed to peripheral paralysis);
• no drooping eyebrow (unlike peripheral paralysis);
• there is no smoothness of the frontal folds (unlike peripheral paralysis);
• preserved conjunctival reflex (due to preserved innervation of the orbicularis oculi muscle);
• smoothness of the nasolabial fold on the side opposite to the lesion;
• inability to tightly compress the lips on the side opposite to the lesion;
• loss of food from the mouth when chewing on the side opposite to the lesion.

Secretory parasympathetic fibers of the facial nerve stimulate the secretion of the submandibular, sublingual and lacrimal glands, as well as the glands of the mucous membrane of the nasopharynx, hard and soft palate.

Efferent parasympathetic fibers originate from a diffuse cluster of neurons in the caudal pons, located under the motor nucleus of the facial nerve. These clusters of neurons are called the superior salivary nucleus (nucl. salivatorius superior) and the lacrimal nucleus (nucl. lacrimalis). The axons of these neurons emerge as part of the intermediate nerve.

P The intermediate nerve leaves the brainstem lateral to the motor root of the facial nerve. In the canal of the facial nerve, the autonomic fibers are divided into two bundles - the greater petrosal nerve (innervates the lacrimal gland, as well as the glands of the nose and palate) and the chorda tympani (innervates the submandibular and sublingual salivary glands).

The chorda tympani also contains sensitive fibers (special taste sensitivity) to the anterior 2/3 of the tongue. Separating from the geniculate ganglion, the greater petrosal nerve goes forward and medially, exits the temporal bone through the cleft of the greater petrosal nerve canal and passes along the groove of the same name to the foramen lacerum. Through it, the nerve reaches the base of the skull, where it connects with the deep petrosal nerve (n. petrosus profundus) from the sympathetic plexus of the internal carotid artery. Their fusion leads to the formation of the nerve of the pterygoid canal (n. canalis pterygoidei, Vidian nerve), passing along the pterygoid canal to the pterygopalatine ganglion (gangl. pterigopalatinum).In the area of ​​the node, the nerve of the pterygoid canal connects with the maxillary nerve (V 2 ).

Postganglionic fibers extending from the neurons of the pterygopalatine ganglion, through the zygomatic and zygomaticotemporal nerves, reach the lacrimal nerve (n. lacrimalis, V 1), which innervates the lacrimal gland. Thus, the parasympathetic innervation of the lacrimal gland occurs independently of the innervation of the eyeball and is largely associated with the innervation of the salivary glands.

The ciliary ganglion plays vital role in providing sensitive, sympathetic and parasympathetic innervation of the orbital structures. This is a flattened quadrangular formation measuring 2 mm, adjacent to the outer surface of the optic nerve, located 10 mm from the optic opening and 15 mm from the posterior pole of the eye.

The ciliary node has three roots

• A well-defined sensory root contains sensory fibers from the cornea, iris and ciliary body, which are part of the nasociliary nerve (V 1);
• Parasympathetic (motor) root as part of the external branch of the lower branch n. III reaches the ciliary ganglion, where it forms synaptic transmission and leaves the ciliary ganglion in the form of short ciliary nerves innervating the constrictor pupillary muscle and the ciliary muscle;
• The thin sympathetic root of the ciliary ganglion, the structure of which, like the entire sympathetic system of the orbit, has not been fully studied.

The sympathetic innervation of the eye originates in the ciliary spinal center of Budge (lateral horns C8-Th2). The fibers coming out from here rise upward - to the superior cervical ganglion, where they switch to the next neuron, the axons of which form a plexus on the internal carotid artery (plexus caroticus internus). The sympathetic fibers that leave the ICA siphon enter the abducens nerve root, but soon move from it to the nasociliary nerve, with which they enter the orbit through the superior orbital fissure, passing in transit through the ciliary ganglion. As long ciliary nerves, they innervate the dilator muscle and possibly the choroidal vessels. The second portion of sympathetic fibers enters the orbit along with the ophthalmic artery and innervates the superior and inferior muscles of the eyelid cartilage, Müller's orbital muscle, orbital vessels, sweat glands and, possibly, the lacrimal gland.

Innervation of conjugate eye movements

The center of horizontal gaze (pontine center of gaze) lies in the paramedian reticular formation of the pons near the nucleus of the abducens nerve. Through the medial longitudinal fasciculus, it sends commands to the ipsilateral nucleus of the abducens nerve and the contralateral nucleus of the oculomotor nerve. As a result, the ipsilateral lateral rectus muscle is commanded to abduct, and the contralateral medial rectus muscle is commanded to adduct. In addition to the oculomotor muscles, the medial longitudinal fasciculus connects the anterior and posterior groups of cervical muscles, fibers from the vestibular and basal ganglia, as well as fibers of the cerebral cortex into a single functional complex.

Other potential centers for reflex horizontal conjugal eye movements are fields 18 and 19 of the occipital lobe of the cerebrum, and for voluntary movements - field 8 according to Brodmann.

The center of vertical gaze is apparently located in the reticular formation of the periaqueductal gray substance of the midbrain at the level of the superior colliculi and consists of several specialized nuclei.

• IN back wall The third ventricle contains the prestitial nucleus, which provides upward gaze.
• The nucleus of the posterior commissure (Darksevic) is responsible for downward gaze.
• The intermediate (interstitial) nucleus of Cajal and the nucleus of Darkshevich provide conjugal rotatory movements of the eyes.

It is possible that concomitant vertical eye movements are also provided by neuronal clusters on the anterior border of the superior colliculus. The Darkshevich nucleus and the Cajal nucleus are integration subcortical centers of gaze. From them begins the medial longitudinal fascicle, which includes fibers from the III, IV, VI, VIII, XI pairs of cranial nerves and the cervical plexus.

Thanks to the human visual organs, it perceives almost all information. Innervation of the eye is a very important anatomical and physiological process that provides the motor and sensory functions of the visual apparatus and surrounding tissues. When the supply of the eye structures with nerves interacting with the central nervous system changes, the functioning of the nerve endings is disrupted, which leads to deterioration of vision.

Anatomy of the neural network

The functioning of the visual system is regulated by the human brain. Innervation of the eyeball, circumference and muscles of the eye occurs through 5 pairs of cranial nerves:

• facial;
• diverting;
• block;
• oculomotor;
• trigeminal

The trigeminal nerve is considered one of the largest and most massive nerves. Its branches innervate the nose, upper and lower jaws, eyes, infraorbital, and zygomatic areas. The motor innervation of the organs of vision is carried out by oculomotor nerve fibers, which begin from the brain and supply nerves to the orbit. The sphincter of the pupil is innervated by a nerve that branches off in small branches from the oculomotor process.

Types and functions

The innervation of the eye has many functions and types that are responsible for the normal functioning of the visual system.

Sympathetic, parasympathetic, central make up the entire autonomic nervous system. The sympathetic division innervates the eyeball and adjacent tissues. Parasympathetic innervation occurs due to the third and seventh pairs of the cranial nerves. It is customary to divide the nerves of the ocular structures into sensory, motor and autonomic. Sensitive innervation is a response to external stimuli, as well as allergens within the organ of vision itself, and the regulation of certain metabolic processes. Motor - responsible for the tone of the muscles of the eyeball, upper and lower eyelids, and control the expansion of the palpebral fissure. The lacrimal glands obey the secretory muscles. Autonomic fibers control the degree of expansion and the diameter of the opening in the iris.

The pupillary sphincter is innervated by a nerve that controls the diameter. The pupillary dilator or dilator muscle is responsible for dilation. The main innervation of the eyes is carried out by the 3rd-7th pairs of cranial nerves. These innervating fibers are either motor or sensory in nature.

Causes and symptoms of pathology

There are many factors that provoke damage to the organs of vision. Often these are inflammatory diseases - neuritis, neuralgia. Toxic damage may also occur, for example, tobacco smoke entering the eyes or vapors of harmful substances, the influence of alcohol. Developing and tumor processes nerve endings, muscles, internal and external appendages.

The anatomy of the eyes is designed in such a way that disease of the visual apparatus is not a separate, limited process, but often includes illness of other organs and systems.

If vision deteriorates and there are problems with the perception of objects, it is recommended to undergo an examination by an ophthalmologist, who will identify abnormalities.

A large percentage of pathologies are caused by congenital genetic abnormalities or diseases associated with disruption of the oculomotor nerve: nystagmus, accommodation spasm, strabismus, amblyopia, ophthalmoplegia. The main signs of failure of the innervation of the eyes include disruption of the movement of moisture in the organ, increased IOP, changes in the structure of the fundus, and the appearance of a limited field of vision. A person often ceases to distinguish objects at different distances or movements of the eyeballs occur randomly and at a fast pace. Very often the outcome of such pathological processes leads to blindness, especially without adequate treatment. Therefore, for any problems with visual perception, consultation with an ophthalmologist is necessary.

Diagnosis and treatment

Therapy for any disease comes down to reducing pain and, ideally, full recovery. In case of disruption of the innervation of the ocular structures, before use medicines it is necessary to undergo an examination: Depending on the identified ailment, the doctor prescribes treatment, one of the types of which is medication.

The treatment regimen for various pathologies of the visual organs is different, but its principle is the same for all groups - the effect of the irritating factor must be eliminated. After determining how the eye is innervated and establishing the causes pathological change, the main signs of damage, the doctor selects the optimal drug therapy, laser correction or other treatment methods.

17-09-2011, 13:32

Description

Sensitive innervation of the eye and orbital tissues is carried out by the first branch of the trigeminal nerve - the orbital nerve, which enters the orbit through the superior orbital fissure and is divided into 3 branches: lacrimal, nasociliary and frontal.

The lacrimal nerve innervates the lacrimal gland, the outer parts of the conjunctiva of the eyelids and eyeball, and the skin of the lower and upper eyelids.

The nasociliary nerve gives off a branch to the ciliary ganglion, 3-4 long ciliary branches go to the eyeball, in the suprachoroidal space near the ciliary body they form a dense plexus, the branches of which penetrate the cornea. At the edge of the cornea, they enter the middle sections of its own substance, losing their myelin coating. Here the nerves form the main plexus of the cornea. Its branches under the anterior border plate (Bowman's) form one plexus of the “closing chain” type. The stems coming from here, piercing the border plate, fold on its anterior surface into the so-called subepithelial plexus, from which branches extend, ending with terminal sensory devices directly in the epithelium.

The frontal nerve is divided into two branches: supraorbital and supratrochlear. All branches, anastomosing among themselves, innervate the middle and inner part of the skin of the upper eyelid.

Ciliary, or ciliary, the node is located in the orbit on the outside of the optic nerve at a distance of 10-12 mm from the posterior pole of the eye. Sometimes there are 3-4 nodes around the optic nerve. The ciliary ganglion includes sensory fibers of the nasopharynx nerve, parasympathetic fibers of the oculomotor nerve and sympathetic fibers of the plexus of the internal carotid artery.

4-6 short ciliary nerves depart from the ciliary ganglion, penetrating the eyeball through the posterior part of the sclera and supplying the eye tissue with sensitive parasympathetic and sympathetic fibers. Parasympathetic fibers innervate the sphincter of the pupil and the ciliary muscle. Sympathetic fibers go to the dilator muscle.

The oculomotor nerve innervates all the rectus muscles except the external one, as well as the inferior oblique, levator superior pallidum, sphincter pupillary muscle, and ciliary muscle.

The trochlear nerve innervates the superior oblique muscle, and the abducens nerve innervates the external rectus muscle.

The orbicularis oculi muscle is innervated by a branch of the facial nerve.

Adnexa of the eye

The appendage apparatus of the eye includes the eyelids, conjunctiva, tear-producing and tear-draining organs, and retrobulbar tissue.

Eyelids (palpebrae)

The main function of the eyelids is protective. The eyelids are a complex anatomical formation that includes two layers - musculocutaneous and conjunctival-cartilaginous.

The skin of the eyelids is thin and very mobile, freely gathers into folds when opening the eyelids and also freely straightens when they close. Due to mobility, the skin can easily be pulled to the sides (for example, by scars, causing eversion or inversion of the eyelids). The displaceability, mobility of the skin, the ability to stretch and move are used in plastic surgery.

Subcutaneous tissue is represented by a thin and loose layer, poor in fatty inclusions. As a result, severe swelling easily occurs here due to local inflammatory processes, and hemorrhages due to injuries. When examining a wound, it is necessary to remember about the mobility of the skin and the possibility of large displacement of the wounding object in the subcutaneous tissue.

The muscular part of the eyelid consists of the orbicularis palpebral muscle, the levator palpebrae superioris, the Riolan muscle (a narrow strip of muscle along the edge of the eyelid at the root of the eyelashes) and the Horner muscle (muscle fibers from the orbicularis muscle that surround the lacrimal sac).

The orbicularis oculi muscle consists of the palpebral and orbital bundles. The fibers of both bundles begin from the internal ligament of the eyelids - a powerful fibrous horizontal cord, which is the formation of the periosteum of the frontal process of the upper jaw. The fibers of the palpebral and orbital parts run in arcuate rows. The fibers of the orbital part in the area of ​​the outer corner pass to the other eyelid and form a complete circle. The orbicularis muscle is innervated by the facial nerve.

The muscle that lifts the upper eyelid consists of 3 parts: the anterior part is attached to the skin, the middle part is attached to the upper edge of the cartilage, and the posterior part is attached to the upper fornix of the conjunctiva. This structure ensures the simultaneous lifting of all layers of the eyelids. The anterior and posterior parts of the muscle are innervated by the oculomotor nerve, the middle by the cervical sympathetic nerve.

Behind the orbicularis oculi muscle is a dense connective tissue plate called eyelid cartilage, although it does not contain cartilage cells. The cartilage gives the eyelids a slight bulge that follows the shape of the eyeball. The cartilage is connected to the edge of the orbit by a dense tarso-orbital fascia, which serves as the topographic boundary of the orbit. The contents of the orbit include everything that lies behind the fascia.

In the thickness of the cartilage, perpendicular to the edge of the eyelids, there are modified sebaceous glands - meibomian glands. Their excretory ducts exit into the intermarginal space and are located along the posterior edge of the eyelids. The secretion of the meibomian glands prevents the overflow of tears over the edges of the eyelids, forms a lacrimal stream and directs it into the lacrimal lake, protects the skin from maceration, and is part of the precorneal film that protects the cornea from drying out.

The blood supply to the eyelids is carried out from the temporal side by branches from the lacrimal artery, and from the nasal side - from the ethmoid artery. Both are terminal branches of the ophthalmic artery. The greatest accumulation of eyelid vessels is located 2 mm from its edge. This must be taken into account when surgical interventions and injuries, as well as the location of the muscle bundles of the eyelids. Considering the high displacement capacity of eyelid tissues, minimal removal of damaged areas during primary surgical treatment is desirable.

The outflow of venous blood from the eyelids goes to the superior ophthalmic vein, which has no valves and anastomoses through the angular vein with the cutaneous veins of the face, as well as with the veins of the sinuses and pterygopalatine fossa. The superior orbital vein leaves the orbit through the superior orbital fissure and flows into the cavernous sinus. Thus, an infection from the skin of the face and sinuses can quickly spread to the orbit and into the cavernous sinus.

The regional lymph node of the upper eyelid is the submandibular lymph node, and the lower one is the submandibular lymph node. This must be taken into account during the spread of infection and metastasis of tumors.

Conjunctiva

The conjunctiva is the thin mucous membrane that lines the back surface of the eyelids and the front surface of the eyeball up to the cornea. The conjunctiva is a mucous membrane richly supplied with vessels and nerves. She easily responds to any irritation.

The conjunctiva forms a slit-like cavity (bag) between the eyelid and the eye, which contains the capillary layer of tear fluid.

In the medial direction, the conjunctival sac reaches the inner corner of the eye, where the lacrimal caruncle and the semilunar fold of the conjunctiva (vestigial third eyelid) are located. Laterally, the border of the conjunctival sac extends beyond the outer corner of the eyelids. The conjunctiva performs protective, moisturizing, trophic and barrier functions.

There are 3 sections of the conjunctiva: the conjunctiva of the eyelids, the conjunctiva of the fornix (upper and lower) and the conjunctiva of the eyeball.

The conjunctiva is a thin and delicate mucous membrane, consisting of a superficial epithelial and deep submucosal layer. The deep layer of the conjunctiva contains lymphoid elements and various glands, including lacrimal glands, which provide mucin and lipids for the superficial tear film covering the cornea. The accessory lacrimal glands of Krause are located in the conjunctiva of the superior fornix. They are responsible for the constant production of tear fluid under normal, non-extreme conditions. Glandular formations can become inflamed, which is accompanied by hyperplasia of lymphoid elements, an increase in glandular discharge and other phenomena (folliculosis, follicular conjunctivitis).

The conjunctiva of the eyelids (tun. conjunctiva palpebrarum) is moist, pale pinkish in color, but quite transparent, through it you can see the translucent glands of the cartilage of the eyelids (meibomian glands). The surface layer of the conjunctiva of the eyelid is lined with multirow columnar epithelium, which contains a large number of goblet cells that produce mucus. Under normal physiological conditions there is little of this mucus. Goblet cells respond to inflammation by increasing their numbers and increasing secretion. When the conjunctiva of the eyelid becomes infected, the goblet cell discharge becomes mucopurulent or even purulent.

In the first years of life in children, the conjunctiva of the eyelids is smooth due to the absence of adenoid formations here. With age, you observe the formation of focal accumulations of cellular elements in the form of follicles, which determine special forms follicular lesions of the conjunctiva.

An increase in glandular tissue predisposes to the appearance of folds, depressions and elevations that complicate the surface relief of the conjunctiva, closer to its arches; in the direction of the free edge of the eyelids, the folding is smoothed out.

Conjunctiva of the fornix. In the fornix (fornix conjunctivae), where the conjunctiva of the eyelids passes into the conjunctiva of the eyeball, the epithelium changes from multilayered cylindrical to multilayered flat.

Compared to other sections in the vault area, the deep layer of the conjunctiva is more pronounced. Numerous glandular formations are well developed here, including small additional lacrimal jelly (Krause's glands).

Under the transitional folds of the conjunctiva there is a pronounced layer of loose fiber. This circumstance determines the ability of the conjunctiva of the fornix to easily fold and straighten, which allows the eyeball to maintain full mobility.

Cicatricial changes in the conjunctival fornix limit eye movements. Loose fiber under the conjunctiva contributes to the formation of edema here during inflammatory processes or congestive vascular phenomena. The upper conjunctival fornix is ​​wider than the lower one. The depth of the first is 10-11 mm, and the second - 7-8 mm. Typically, the superior fornix of the conjunctiva extends beyond the superior orbitopalpebral groove, and the inferior fornix is ​​at the level of the inferior orbitopalpebral fold. In the upper outer part of the upper fornix, pinholes are visible, these are the mouths of the excretory ducts of the lacrimal gland

Conjunctiva of the eyeball (conjunctiva bulbi). It distinguishes between a movable part, covering the eyeball itself, and a part of the limbus region, fused to the underlying tissue. From the limbus, the conjunctiva passes to the anterior surface of the cornea, forming its epithelial, optically completely transparent layer.

The genetic and morphological similarity of the epithelium of the conjunctiva of the sclera and cornea determines the possibility of the transition of pathological processes from one part to another. This occurs with trachoma even in its initial stages, which is essential for diagnosis.

In the conjunctiva of the eyeball, the adenoid apparatus of the deep layer is poorly represented; it is completely absent in the cornea area. The stratified squamous epithelium of the conjunctiva of the eyeball is non-keratinizing and under normal physiological conditions retains this property. The conjunctiva of the eyeball is much more abundant than the conjunctiva of the eyelids and fornix, equipped with sensitive nerve endings (the first and second branches of the trigeminal nerve). In this regard, the entry into the conjunctival sac of even small foreign bodies or chemicals causes very unpleasant feeling. It is more significant with inflammation of the conjunctiva.

The conjunctiva of the eyeball is not connected to the underlying tissues in the same way everywhere. Along the periphery, especially in the upper outer part of the eye, the conjunctiva lies on a layer of loose tissue and here it can be freely moved with an instrument. This circumstance is used when performing plastic surgeries when moving sections of the conjunctiva is required.

Along the perimeter of the limbus, the conjunctiva is fixed quite firmly, as a result of which, with significant swelling, a vitreous shaft is formed in this place, sometimes hanging over the edges of the cornea.

The vascular system of the conjunctiva is part of the general circulatory system of the eyelids and eyes. The main vascular distributions are located in its deep layer and are represented mainly by links of the microcircular network. Many intramural blood vessels of the conjunctiva ensure the vital activity of all its structural components.

By changing the pattern of blood vessels in certain areas of the conjunctiva (conjunctival, pericorneal and other types of vascular injections) it is possible differential diagnosis diseases associated with the pathology of the eyeball itself, with diseases of purely conjunctival origin.

The conjunctiva of the eyelids and eyeball is supplied with blood from the arterial arches of the upper and lower eyelids and from the anterior ciliary arteries. The arterial arches of the eyelids are formed from the lacrimal and anterior ethmoidal arteries. The anterior ciliary vessels are branches of the muscular arteries that supply blood to the external muscles of the eyeball. Each muscular artery gives off two anterior ciliary arteries. An exception is the artery of the external rectus muscle, which gives off only one anterior ciliary artery.

These vessels of the conjunctiva, the source of which is the ophthalmic artery, belong to the system of the internal carotid artery. However, the lateral arteries of the eyelids, from which branches supplying part of the conjunctiva of the eyeball arise, anastomose with the superficial temporal artery, which is a branch of the external carotid artery.

The blood supply to most of the conjunctiva of the eyeball is carried out by branches originating from the arterial arches of the upper and lower eyelids. These arterial branches and the accompanying veins form conjunctival vessels, which in the form of numerous stems go to the conjunctiva of the sclera from both anterior folds. The anterior ciliary arteries of the scleral tissue run above the area of ​​attachment of the rectus tendons towards the limbus. 3-4 mm from it, the anterior ciliary arteries are divided into superficial and perforating branches, which penetrate through the sclera into the eye, where they participate in the formation of the large arterial circle of the iris.

The superficial (recurrent) branches of the anterior ciliary arteries and the accompanying venous trunks are the anterior conjunctival vessels. The superficial branches of the conjunctival vessels and the posterior conjunctival vessels anastomosing with them form the superficial (subepithelial) body of the vessels of the conjunctiva of the eyeball. This layer contains the greatest number of elements of the microcircular bed of the bulbar conjunctiva.

The branches of the anterior ciliary arteries, anastomosing with each other, as well as the tributaries of the anterior ciliary veins form the marginal circumference of the limbus, or the perilimbal vascular network of the cornea.

Lacrimal organs

The lacrimal organs consist of two separate topographically distinct departments, namely the tear-producing and lacrimal-discharge parts. The tear performs protective (washes out foreign elements from the conjunctival sac), trophic (nourishes the cornea, which does not have its own vessels), bactericidal (contains nonspecific immune defense factors - lysozyme, albumin, lactoferin, b-lysine, interferon), moisturizing functions (especially the cornea , maintaining its transparency and being part of the precorneal film).

Tear-producing organs.

Lacrimal gland (glandula lacrimalis) in its anatomical structure it is very similar to the salivary glands and consists of many tubular glands, collected in 25-40 relatively separate lobules. The lacrimal gland, by the lateral portion of the aponeurosis of the muscle that lifts the upper eyelid, is divided into two unequal parts, the orbital and palpebral, which communicate with each other by a narrow isthmus.

The orbital part of the lacrimal gland (pars orbitalis) is located in the upper outer part of the orbit along its edge. Its length is 20-25 mm, diameter is 12-14 mm and thickness is about 5 mm. In shape and size, it resembles a bean, which is adjacent with its convex surface to the periosteum of the lacrimal fossa. The gland is covered in front by the tarso-orbital fascia, and in the back it is in contact with the orbital tissue. The gland is held in place by connective tissue cords stretched between the gland capsule and the periorbita.

The orbital part of the gland is usually not palpable through the skin, since it is located behind the bony edge of the orbit that hangs here. When the gland enlarges (for example, tumor, swelling or prolapse), palpation becomes possible. The lower surface of the orbital part of the gland faces the aponeurosis of the muscle that lifts the upper eyelid. The consistency of the gland is soft, the color is grayish-red. The lobes of the anterior part of the gland are closed more tightly than in its posterior part, where they are loosened by fatty inclusions.

3-5 excretory ducts of the orbital part of the lacrimal gland pass through the substance of the inferior lacrimal gland, receiving part of its excretory ducts.

Palpebral or secular part The lacrimal gland is located somewhat anteriorly and below the superior lacrimal gland, directly above the superior fornix of the conjunctiva. When turned inside out upper eyelid and turning the eye inward and downward, the lower lacrimal gland is normally visible in the form of a slight protrusion of a yellowish tuberous mass. In the case of inflammation of the gland (dacryoadenitis), a more pronounced bulge is found in this place due to swelling and compaction of the glandular tissue. The increase in the mass of the lacrimal gland can be so significant that it sweeps away the eyeball.

The lower lacrimal gland is 2-2.5 times smaller than the upper lacrimal gland. Its longitudinal size is 9-10 mm, transverse - 7-8 mm and thickness - 2-3 mm. The anterior edge of the inferior lacrimal gland is covered with conjunctiva and can be palpated here.

The lobules of the lower lacrimal gland are loosely connected to each other, its ducts partly merge with the ducts of the upper lacrimal gland, some open into the conjunctival sac independently. Thus, there are a total of 10-15 excretory ducts of the upper and lower lacrimal glands.

Excretory ducts both lacrimal glands are concentrated in one small area. Scar changes in the conjunctiva in this place (for example, with trachoma) may be accompanied by obliteration of the ducts and lead to a decrease in the lacrimal fluid secreted into the conjunctival sac. The lacrimal gland comes into action only in special cases when a lot of tears are needed (emotions, foreign agents entering the eye).

In normal condition, to perform all functions, 0.4-1.0 ml of tears produce small accessory lacrimal glands Krause (20 to 40) and Wolfring (3-4), embedded in the thickness of the conjunctiva, especially along its upper transitional fold. During sleep, tear secretion slows down sharply. Small conjunctival lacrimal glands, located in the boulevard conjunctiva, provide the production of mucin and lipids necessary for the formation of the precorneal tear film.

Tear is a sterile, clear, slightly alkaline (pH 7.0-7.4) and somewhat opalescent liquid, consisting of 99% water and approximately 1% organic and inorganic parts (mainly sodium chloride, but also sodium carbonates and magnesium, calcium sulfate and phosphate).

With various emotional manifestations, the lacrimal glands, receiving additional nerve impulses, produce excess fluid that flows from the eyelids in the form of tears. There are persistent disturbances in tear secretion towards hyper- or, conversely, hyposecretion, which is often a consequence of pathology of nerve conduction or excitability. Thus, tear production decreases with paralysis of the facial nerve (VII pair), especially with damage to its geniculate ganglion; trigeminal nerve palsies (V pair), as well as in some poisonings and severe infectious diseases With high temperature. Chemical, painful temperature irritations of the first and second branches of the trigeminal nerve or zones of its innervation - the conjunctiva, the anterior parts of the eye, the mucous membrane of the nasal cavity, and the dura mater are accompanied by profuse lacrimation.

The lacrimal glands have sensitive and secretory (vegetative) innervation. General sensitivity of the lacrimal glands (provided by the lacrimal nerve from the first branch of the trigeminal nerve). Secretory parasympathetic impulses are delivered to the lacrimal glands by fibers of the intermediate nerve (n. intermedrus), which is part of the facial nerve. Sympathetic fibers to the lacrimal gland originate from the cells of the superior cervical sympathetic ganglion.

Lacrimal ducts.

They are designed to drain tear fluid from the conjunctival sac. Tear as an organic liquid ensures the normal vital activity and function of the anatomical formations that make up the conjunctival cavity. The excretory ducts of the main lacrimal glands open, as mentioned above, into the lateral section of the upper fornix of the conjunctiva, which creates a semblance of a lacrimal “shower”. From here, the tear spreads throughout the conjunctival sac. The posterior surface of the eyelids and the anterior surface of the cornea limit the capillary gap - the lacrimal stream (rivus lacrimalis). By moving the eyelids, the tear moves along the tear stream towards the inner corner of the eye. Here is the so-called lacrimal lake (lacus lacrimalis), limited by the medial areas of the eyelids and the semilunar fold.

The lacrimal ducts themselves include lacrimal openings (punctum lacrimale), lacrimal canaliculi (canaliculi lacrimales), lacrimal sac (saccus lacrimalis), and nasolacrimal duct (ductus nasolacrimalis).

Lacrimal puncta(punctum lacrimale) are the initial openings of the entire lacrimal apparatus. Their normal diameter is about 0.3 mm. The lacrimal puncta are located at the top of small conical projections called lacrimal papillae (papilla lacrimalis). The latter are located on the posterior ribs of the free edge of both eyelids, the upper one is approximately 6 mm, and the lower one is 7 mm from their internal commissure.

The lacrimal papillae face the eyeball and are almost adjacent to it, while the lacrimal puncta are immersed in the lacrimal lake, at the bottom of which lies the lacrimal caruncle (caruncula lacrimalis). Close contact of the eyelids, and therefore the lacrimal openings with the eyeball, is facilitated by constant tension of the tarsal muscle, especially its medial sections.

The holes located at the top of the lacrimal papillae lead into the corresponding thin tubes - superior and inferior lacrimal canaliculi. They are located entirely in the thickness of the eyelids. In direction, each tubule is divided into a short oblique vertical and a longer horizontal part. The length of the vertical sections of the lacrimal canaliculi does not exceed 1.5-2 mm. They run perpendicular to the edges of the eyelids, and then the tear ducts turn towards the nose, taking a horizontal direction. The horizontal sections of the tubules are 6-7 mm long. The lumen of the lacrimal canaliculi is not the same throughout. They are somewhat narrowed in the bending area and ampullarly widened at the beginning of the horizontal section. Like many other tubular formations, the lacrimal canaliculi have a three-layer structure. The outer, adventitial membrane is composed of delicate, thin collagen and elastic fibers. The middle muscular layer is represented by a loose layer of bundles of smooth muscle cells, which apparently play a certain role in regulating the lumen of the tubules. The mucous membrane, like the conjunctiva, is lined with columnar epithelium. This arrangement of the lacrimal canaliculi allows them to stretch (for example, under mechanical influence - the introduction of conical probes).

The terminal sections of the lacrimal canaliculi, each individually or merging with each other, open into the upper section of a wider reservoir - the lacrimal sac. The mouths of the lacrimal canaliculi usually lie at the level of the medial commissure of the eyelids.

Lacrimal sac(saccus lacrimale) makes up the upper, expanded part of the nasolacrimal duct. Topographically, it relates to the orbit and is located in its medial wall in the bone recess - the fossa of the lacrimal sac. The lacrimal sac is a membranous tube 10-12 mm long and 2-3 mm wide. Its upper end ends blindly; this place is called the vault of the lacrimal sac. In the downward direction, the lacrimal sac narrows and passes into the nasolacrimal duct. The wall of the lacrimal sac is thin and consists of a mucous membrane and a loose submucosal layer connective tissue. The inner surface of the mucous membrane is lined with multirow columnar epithelium with a small number of mucous glands.

The lacrimal sac is located in a kind of triangular space formed by various connective tissue structures. The sac is limited medially by the periosteum of the lacrimal fossa, covered in front by the internal ligament of the eyelids and the tarsal muscle attached to it. The tarso-orbital fascia runs behind the lacrimal sac, as a result of which it is believed that the lacrimal sac is located preseptally, in front of the septum orbitale, i.e., outside the orbital cavity. In this regard, purulent processes of the lacrimal sac extremely rarely give complications to the tissues of the orbit, since the sac is separated from its contents by a dense fascial septum - a natural obstacle to infection.

In the area of ​​the lacrimal sac, under the skin of the internal angle, there passes a large and functionally important vessel - the angular artery (a.angularis). It is the connecting link between the systems of the external and internal carotid arteries. The angular vein is formed at the inner corner of the eye, which then continues into the facial vein.

Nasolacrimal duct(ductus nasolacrimalis) is a natural continuation of the lacrimal sac. Its length is on average 12-15 mm, width 4 mm, the duct is located in the bone canal of the same name. The general direction of the channel is from top to bottom, front to back, outside to inside. The course of the nasolacrimal duct varies somewhat depending on the width of the nasal bridge and pear-shaped opening skulls

Between the wall of the nasolacrimal duct and the periosteum of the bony canal there is a densely branched network of venous vessels, this is a continuation of the cavernous tissue of the inferior turbinate. Venous formations are especially developed around the mouth of the duct. Increased blood filling of these vessels as a result of inflammation of the nasal mucosa causes temporary compression of the duct and its outlet, which prevents tears from moving into the nose. This phenomenon is well known to everyone as lacrimation during an acute runny nose.

The mucous membrane of the duct is lined with two-layer columnar epithelium; small branched tubular glands are found here. Inflammatory processes and ulceration of the mucous membrane of the nasolacrimal duct can lead to scarring and its persistent narrowing.

The lumen of the outlet end of the nasolacrimal duct has a slit-like shape: its opening is located in the front part of the lower nasal meatus, 3-3.5 cm away from the entrance to the nose. Above this opening there is a special fold called the lacrimal fold, which represents a duplication of the mucous membrane and prevents the reverse flow of tear fluid.

In the prenatal period, the mouth of the nasolacrimal duct is closed by a connective tissue membrane, which resolves by the time of birth. However, in some cases, this membrane may persist, which requires urgent measures to remove it. Delay threatens the development of dacryocystitis.

The tear fluid, irrigating the front surface of the eye, partially evaporates from it, and the excess collects in the tear lake. The mechanism of tear production is closely related to the blinking movements of the eyelids. the main role in this process is attributed to the pump-like action of the lacrimal canaliculi, the capillary lumen of which, under the influence of the tone of their intramural muscular layer, associated with the opening of the eyelids, expands and sucks in fluid from the lacrimal lake. When the eyelids close, the canaliculi are compressed and the tear is squeezed into the lacrimal sac. Of no small importance is the suction effect of the lacrimal sac itself, which during blinking movements alternately expands and contracts due to the traction of the medial ligament of the eyelids and the contraction of part of their circular muscle, known as Horner’s muscle. Further outflow of tears along the nasolacrimal duct occurs as a result of the expelling action of the lacrimal sac, and also partly under the influence of gravity.

The passage of tear fluid through the lacrimal ducts under normal conditions lasts about 10 minutes. Approximately this amount of time is required for (3% collargol, or 1% fluorecein) from the lacrimal lake to reach the lacrimal sac (5 minutes - canalicular test) and then the nasal cavity (5 minutes - positive nasal test).