TO major salivary glands (glandulae salivariae majores) include paired parotid, sublingual and submandibular glands.

Large salivary glands belong to parenchymal organs, which include:

parenchyma- a specialized (secretory) part of the gland, represented by the acinar section containing secretory cells where secretion is produced. Part salivary glands includes mucous cells that secrete a thick mucous secretion, and serous cells that secrete liquid, watery, so-called serous or protein saliva. The secretion produced in the glands is delivered through the system of excretory ducts to the surface of the mucous membrane in different parts of the oral cavity.

stroma- a complex of connective tissue structures that form the internal frame of the organ and contribute to the formation of lobules and lobes; in the layers of connective tissue there are vessels and nerves leading to the acinar cells.

Parotid gland

Parotid gland (glandula parotidea) is the largest of the salivary glands, which is located downward and anterior to auricle, at the posterior edge of the masticatory muscle. Here it is easily accessible for palpation.

Sometimes there may also be an accessory parotid gland (glandula parotidea accessoria), located on the surface of the masseter muscle near the duct parotid gland. The parotid gland is a complex multilobulated alveolar gland consisting of serous cells that produce serous (protein) saliva. It distinguishes between the superficial part (pars superficialis) and the deep part (pars profunda).

The superficial part of the gland has a chewing process and is located on the branch lower jaw and on the masticatory muscle. Sometimes there is also a superior process adjacent to the cartilaginous portion of the external auditory canal. The deep part often has pharyngeal and posterior processes. It is located in the mandibular fossa (fossa retromandibularis), where it is adjacent to the temporomandibular joint, the mastoid process of the temporal bone and some neck muscles.

The parotid gland is covered by the parotid fascia, which forms the capsule of the gland. The capsule consists of superficial and deep layers covering the gland from the outside and inside. It is closely connected to the gland by connective tissue bridges that continue into septa that separate the lobules of the gland from each other. The deep layer of the capsule in the area of ​​the pharyngeal process is sometimes absent, which creates conditions for the purulent process to spread into the peripharyngeal space during parotitis.

Parotid duct(ductus parotideus), or Stenon's duct The name "Stenon's duct" is derived from the name of the anatomist who described it. Such anatomical terms are called eponyms. Eponyms are often used in clinical practice along with nomenclature anatomical terms., is formed by the fusion of interlobar ducts and reaches a diameter of 2 mm. Leaving the gland at its anterior edge, it lies on masticatory muscle 1 cm below the zygomatic arch, pierces the buccal muscle and opens on the mucous membrane of the cheek into the vestibule of the mouth at the level of the 1st-2nd upper molars. The accessory parotid gland is usually located above the parotid duct, into which its own duct flows.

Passes through the thickness of the parotid gland external carotid artery And submandibular vein. Inside the gland, the external carotid artery divides into two terminal branches - maxillary And superficial temporal artery.

Also passes through the parotid gland facial nerve. In it, it is divided into a number of branches radiating from the earlobe area to the facial muscles.

Blood supply parotid salivary gland is carried out by branches external carotid artery(a. carotis externa), among which posterior auricular artery(a. auricularis posterior), passing obliquely backward over the upper edge of the posterior belly of the digastric muscle, transverse artery of the face(a. transversa faciei) and zygomaticoorbital artery(a. zygomaticoorbitalis), extending from superficial temporal artery(a. temporalis superficialis), as well as deep auricular artery(a. auricularis profunda), extending from maxillary artery (a. maxillaris) (see Fig. 10). The excretory duct of the parotid gland is supplied with blood from the transverse artery of the face. The arteries of the parotid gland have numerous anastomoses with each other and with the arteries of nearby organs and tissues.

Venous drainage provided by the veins accompanying the excretory ducts of the gland. Merging, they form parotid veins Ezes (vv. parotideae), carrying blood into mandibular(v. retromandibularis) and facial veins(v. facialis) and further into internal jugular vein(v. jugularis interna).

On the way to the mandibular vein, blood from the upper part of the gland also flows into transverse vein of the face(v. transversa faciei), from its middle and lower part - in masticatory veins(vv. maxillares) and pterygoid plexus(plexus pterygoideus), from the anterior part of the gland - in anterior auricular veins(vv. auriculares anteriores). From the postauricular part of the gland, venous blood flows into posterior auricular vein(v. auricularis posterior), sometimes - in occipital veins(vv. occipitales) and further to external jugular vein(v. jugularis externa).

Lymphatic drainage carried out mainly in deep parotid nodes(nodi parotidei profundi), which includes preauricular, inferior auricular and intraglandular nodes,

and also in superficial parotid nodes(nodi parotidei superficiales). Of these, lymph is directed to superficial And lateral deep cervical ganglia.

Innervation parotid gland is carried out by the parotid branches auriculotemporal nerve(n. auriculotemporalis), extending from mandibular nerve(n. mandibularis - III branch of n. trigeminus). The parotid branches (rr. parotidei) include the sensory ones, the following in the composition trigeminal nerve , and autonomic nerve fibers.

The autonomic innervation of the parotid gland is carried out by parasympathetic postganglionic nerve fibers arising from ear node(ganglion oticum), located on the medial surface of the mandibular nerve under the foramen ovale, and sympathetic postganglionic nerve fibers extending from upper cervical node(ganglion cervicale superius).

Preganglionic parasympathetic nerve fibers originate from inferior salivary nucleus(nucl. salivatorius inf.), located in the medulla oblongata; then in the composition glossopharyngeal nerve(n. glossopharyngeus - IX pair of cranial nerves) and its branches (n. tympanicus, n. petrosus minor) reach ear node(ganglion oticum). From the ear ganglion, postganglionic nerve fibers follow branches in the parotid gland auriculotemporal nerve.

Parasympathetic nerve fibers stimulate the secretion of the gland and dilate its blood vessels.

Preganglionic sympathetic nerve fibers arise from the autonomic nuclei of the upper thoracic segments spinal cord and as part of the sympathetic trunk reach the superior cervical ganglion.

Sympathetic postganglionic nerve fibers come from the superior cervical ganglion and approach the parotid gland as part of plexus of external carotid artery(plexus caroticus externus) along the branches of the external carotid artery supplying blood to the gland. Sympathetic innervation has a constricting effect on blood vessels and inhibits the secretion of the gland.

The secretory function of the salivary glands in animals is studied in acute and chronic experiments. The acute method involves inserting a cannula into the gland duct under anesthesia, through which saliva is released. Chronic (according to Pavlov) - surgical method one of the ducts of the gland is brought out onto the cheek (fistula) and a funnel is fixed to it to collect saliva (Fig. 13.5). experimental methods

RICE. 13.5.

provide an opportunity to study the influence various factors(food, nervous, humoral) on the secretory function of the salivary glands. In humans, a Lashley-Krasnogorsky capsule is used, which is fixed on the mucous membrane of the cheek opposite the gland duct.

Saliva secretion carried out by the salivary glands reflexively.

Parotid the glands, the largest among the salivary glands, form a serous secretion, which contains proteins and a significant amount of water; its quantity is up to 60 % saliva.

Submandibular and sublingual glands produce a mixed serous-mucosal secretion, which includes proteins and mucus - mucin, in an amount of 25-30% and 10-15 % respectively. Small glands of the tongue and oral cavity secrete mainly mucus - mucin.

Per day, the salivary glands produce 0.8-2.0 liters of saliva, which contains water, electrolytes (the same composition as in blood plasma), proteins, enzymes, mucin, protective factors (bactericidal, bacteriostatic), insulin-like protein, parotin . Saliva pH is 6.0-7.4. The dry residue consists of inorganic and organic substances.

■ Enzymes saliva represents: alpha amylase, which begins the hydrolysis of carbohydrates to disaccharides: DNases and RNases- break down amino acids: “lingual” lipase- produced by the salivary glands of the tongue and begins hydrolysis of lipids. A significant group of enzymes (more than 20) are involved in the hydrolysis of substances that form dental plaque, and thereby reduce dental deposits.

■ Mucin is a glycoprotein that protects the oral mucosa from mechanical damage and promotes the formation of food bolus.

The protective factors of saliva include:

1 Lysozyme(muramidase), which destroys bacterial membranes, namely, breaks 1-4 bonds between N-acetyl-muramic acid and N- acetylglucosamine - two main mucopeptides that make up bacterial membranes. Lysozyme enters the oral cavity along with the saliva of large and small salivary glands, with tissue exudate of gingival fluid and from leukocytes that make up the saliva. With a high concentration of lysozyme in the oral cavity, the bacterial flora becomes ineffective.

2 Secretory IgA, less - IgG and IgM. Secretory IgA is produced by the salivary glands and is more resistant to digestive secretions than those found in the blood plasma, while IgM is predominantly an exudate of fluid secreted by the gums. IgA facilitates the aggregation of microbes, forming complexes with epithelial surface proteins, protects it and increases the phagocytic activity of leukocytes.

3 Peroxidases and thiocyanates saliva acts as antibacterial enzymes.

RICE. 13.6.

4 Saliva saturation calcium salts reduces enamel decalcification.

Mechanism of saliva formation , first described by K. Ludwig, indicates that secretion is not a passive filtration of fluid from blood vessels - it is the result of an active function secretory cells. Primary saliva is formed in the acinar cells of the glands. Acinus cells synthesize and secrete enzymes and mucus, spill - form the liquid part of saliva, its ionic composition (Fig. 13.6).

Phases of the secretory cycle. Substances necessary for the synthesis of enzymes, primarily amino acids, penetrate through the basement membrane of the capillary into the secretory cell. The synthesis of prosecrete (the precursor of the enzyme) takes place on ribosomes, from which it is transported to the Golgi apparatus for maturation. The mature secretion is packaged into granules and stored in them until it is released into the lumen of the gland, which is stimulated by Ca 2+ ions.

The liquid part of saliva is formed by ductal cells. At first, it resembles blood plasma, in which there is a high concentration of sodium and chlorine ions and much less potassium and bicarbonate ions. The formation of liquid saliva involves the expenditure of energy using oxygen necessary for the synthesis of ATP. As saliva passes through the ducts, its ionic composition changes - the amount of sodium and chlorine decreases and the amount of potassium and bicarbonate ions increases. The reabsorption of sodium ions and the secretion of potassium ions is regulated by aldosterone (as in the kidney tubules). Ultimately, secondary saliva is formed and secreted into the oral cavity (see Fig. 13.6). Muline digestion is influenced by the level of blood flow in the gland, which depends on the metabolites formed in it, especially kinins (bradykinin), which cause local vasodilation and increased secretion.

In response to the action of various stimuli (with different properties), the salivary glands secrete unequal amounts of saliva, with different compositions. Thus, when eating dry food, a large amount of liquid saliva is released; when consuming liquid (milk), little is produced, but it contains a lot of mucus.

Innervation of the salivary glands carried out by parasympathetic and sympathetic nerves. Parasympathetic innervation of the glands is received from the nuclei of the cranial nerves of the medulla oblongata: parotid - from the lower salivary nucleus - IX pair (glossopharyngeal), submandibular and sublingual - from the upper salivary nucleus - VII pair (facial). Stimulation of the parasympathetic nervous system causes the release of large amounts of liquid saliva, poor in organic substances.

Sympathetic innervation to all salivary glands is provided by the centers of the lateral horns of the II-IV thoracic segments of the spinal cord; through the superior cervical sympathetic ganglion they are directed to the glands. When the sympathetic nerves are activated, little saliva is released, but it contains a high concentration organic matter(enzymes, mucin).

Regulation salivation carried out by folding-reflex mechanisms using:

1 conditioned reflexes the sight and smell of food, the sounds accompanying the act of eating, their center is located in the cerebral cortex (conditioned reflex phase) 2 unconditioned reflexes, associated with irritation of food receptors of the tongue and oral mucosa; their center is located in the salivary nuclei of the medulla oblongata (mad-reflex phase). The afferent input to the central nervous system during the implementation of unconditioned reflexes is the sensory fibers of the V, VII, IX and X pairs of cranial nerves; efferent output - parasympathetic fibers VII, IX pairs and sympathetic neurons of the lateral horns of the II-IV segments of the thoracic region (Fig. 13.7).

Penetrating into the eyeball, sympathetic fibers approach the pupillary dilator. Their function is to dilate the pupil and constrict the blood vessels of the eye. Damage to the efferent sympathetic pathway is accompanied by constriction of the pupil on the same side and dilation of the blood vessels of the eye.

The pathways to the eyeball are also two-neuron. The bodies of the first neurons are located in the accessory nucleus oculomotor nerve. Their axons represent preganglionic fibers, which pass as part of the oculomotor nerve to the ciliary ganglion, where they end on effector neurons. From bodies nerve cells The ciliary ganglion originates from the axons of the second neurons, which represent postganglionic fibers. The latter pass as part of the short ciliary nerves to the ciliary muscle and the muscle that constricts the pupil.

Damage to the parasympathetic efferent pathway leads to loss of the accommodative ability of the eye for distant and near vision of objects and pupil dilation.

INNERVATION OF THE LACRIMAL GLAND

Afferent fibers, conducting impulses from the conjunctiva eyeball and the lacrimal gland, pass into the central nervous system as part of the lacrimal nerve, which is a branch of the optic nerve (from the first branch of the trigeminal nerve). They end on the spinal nucleus of the trigeminal nerve. Next, a connection occurs to the autonomic centers: the upper salivary nucleus and through the reticular formation to the lateral horns of the upper thoracic segments of the spinal cord (Fig. 11).

Efferent sympathetic the pathways to the lacrimal gland are two-neuron. The bodies of the first neurons are located in the lateral intermediate nucleus of the lateral horns of the spinal cord at the level of the upper thoracic segments. Departing from them preganglionic fibers reach the upper cervical node of the sympathetic trunk as part of the white connecting branches and its internodal branches. Postganglionic fibers cells of the upper cervical ganglion pass sequentially through the internal carotid plexus, deep petrosal nerve, and the nerve of the pterygoid canal. Then they go along with the parasympathetic fibers to the maxillary nerve, and through the anastomosis between the zygomatic and lacrimal nerves they reach the lacrimal gland.

Irritation of sympathetic fibers causes a decrease or delay in tear production. The cornea and conjunctiva of the eye become dry.

Efferent parasympathetic the pathways to the lacrimal gland are also two-neuron. The cell bodies of the first neurons lie in the superior salivary nucleus. Preganglionic fibers are directed from the superior salivary nucleus as part of the intermediate nerve together with the facial nerve in the canal of the same name, and then in the form of a large petrosal nerve to the pterygopalatine ganglion, where they end on the second neurons.

Postganglionic fibers The cells of the pterygopalatine ganglion pass as part of the maxillary and zygomatic nerves, and then, through an anastomosis with the lacrimal nerve, to the lacrimal gland.

Irritation of parasympathetic fibers or the superior salivary nucleus is accompanied by an increase in the secretory function of the lacrimal gland. Cutting the fibers can cause cessation of tear production.

INNERVATION OF THE MAJOR SALIVARY GLANDS

Parotid salivary gland.

Afferent fibers begin with sensitive endings in the mucous membrane of the posterior third of the tongue (lingual branch of the IX pair of cranial nerves). The glossopharyngeal nerve conducts taste and general sensitivity to the solitary nucleus located in the medulla oblongata. Interneurons switch the path to the parasympathetic cells of the lower salivary nucleus, and along the reticulospinal path to the cells of the sympathetic centers located in the lateral horns of the upper thoracic segments of the spinal cord (Fig. 12).

Efferent sympathetic preganglionic fibers, sending impulses to the parotid salivary gland, from the lateral intermediate nucleus of the lateral horns of the spinal cord (T 1 - T 2) go as part of the anterior roots of the spinal nerves, white connecting branches to the sympathetic trunk and reach the upper cervical ganglion through interganglionic connections. Here a switch to another neuron occurs. Postganglionic fibers in the form of external carotid nerves, they form a periarterial plexus around the external carotid artery, within which they approach the parotid gland.

Irritation of sympathetic fibers is accompanied by a decrease in the liquid part of saliva secreted, an increase in its viscosity and, accordingly, dry mouth.

Efferent parasympathetic preganglionic fibers begin from the inferior salivary nucleus of the glossopharyngeal nerve, pass into the tympanic nerve, and go through the tympanic canaliculus to tympanic cavity, continue as the lesser petrosal nerve. Through the sphenoid-petrosal fissure, the lesser petrosal nerve leaves the cranial cavity and approaches the auricular ganglion, located next to the mandibular nerve of the V pair of cranial nerves, where they switch to second neurons. Fibers of second neurons ( postganglionic) as part of the auriculotemporal nerve reach the parotid gland.

Parasympathetic fibers conduct impulses that enhance the secretory activity of the parotid salivary glands. Irritation of the nucleus or nerve conductors is accompanied by copious secretion of saliva.

Submandibular and sublingual salivary glands .

Afferent (ascending) fibers begin with sensitive endings in the mucous membrane of the anterior 2/3 of the tongue, and general sensitivity goes along the lingual nerve of the V pair of cranial nerves, and taste sensitivity goes along the fibers of the tympanic chord. The axons of afferent neurons switch on the cells of the solitary nucleus, the processes of which connect with the parasympathetic superior salivary nucleus and the nuclei of the reticular formation. Through the reticulospinal tract, the reflex arc is closed to the centers of the sympathetic nervous system (Th 1 - Th 2).

Saliva secretion is controlled by the autonomic nervous system. Parasympathetic and sympathetic nerves are sent to the salivary glands and reach them by following different routes. Axons inside the glands of various origins arranged in the form of bundles.
Nerve fibers running in the stroma of the glands together with the vessels are directed to the smooth myocytes of the arterioles, the secretory and myoepithelial cells of the coiceal sections, as well as the cells of the intercalary and striated sections. The axons, losing their sheath of Schwann cells, penetrate the basement membrane and are located between the secretory cells of the terminal sections, ending in terminal varicose veins containing vesicles and mitochondria (hypolemmal neuroeffector contact). Some axons do not penetrate the basement membrane, forming varicosities near the secretory cells (epilemmal neuroeffector contact). The fibers innervating the ducts are located predominantly outside the epithelium. The blood vessels of the salivary glands are innervated by sympathetic and parasympathetic axons.
“Classical” neurotransmitters (acetylcholine in parasympathetic and norepinephrine in sympathetic axons) accumulate in small vesicles. Immunohistochemically, a variety of neuropeptide mediators were found in the nerve fibers of the salivary glands, which accumulate in large vesicles with a dense center - substance P, calcitonin gene-related peptide (CABP), vasoactive intestinal peptide (VIP), C-edge peptide of neuropeptide Y (CPON), histidine-methionine peptide (PHM).
The most numerous fibers contain VIP, PGM, CPON. They are located around the end sections, penetrating into them, entwining the excretory ducts and small vessels. Fibers containing PSKG and substance P are much less common. It is assumed that peptidergic fibers are involved in the regulation of blood flow and secretion.
Afferent fibers were also found, which were most numerous around the large ducts; their endings penetrate the basement membrane and are located among the epithelial cells. Substance P-containing unmyelinated and thin myelinated fibers carrying nociceptive signals are located around the terminal sections, blood vessels and excretory ducts.
Nerves have at least four types of effects on the glandular cells of the salivary glands: hydrokinetic (water mobilization), proteokinetic (protein secretion), synthetic (increased synthesis) and trophic (maintaining normal structure and function). In addition to affecting glandular cells, nerve stimulation causes contraction of myoepithelial cells, as well as changes vascular bed(vasomotor effect).
Stimulation of parasympathetic nerve fibers results in the secretion of a significant volume of watery saliva with low protein content and high concentrations of electrolytes. Stimulation of sympathetic nerve fibers causes the secretion of small amounts of viscous saliva with a high mucus content.

Most researchers indicate that the salivary glands are not fully formed at the time of birth; their differentiation is completed mainly by 6 months - 2 years of life, but morphogenesis continues until 16-20 years. At the same time, the nature of the secretion produced may also change: for example, in the parotid gland, during the first years of life, a mucous secretion is produced, which only becomes serous from the 3rd year. After birth, the synthesis of lysozyme and lactoferrin by epithelial cells decreases, but the production of the secretory component progressively increases. At the same time, in the stroma of the gland the number of plasma cells that produce predominantly IgA increases.
After 40 years, the phenomena of age-related involution of glands are observed for the first time. This process intensifies in old age and senility, which is manifested by changes in both the terminal sections and the excretory ducts. The glands, which have a relatively monomorphic structure in youth, are characterized by progressive heteromorphy with age.
With age, the terminal sections acquire greater differences in size, shape and tinctorial properties. The size of the cells of the terminal sections and the content of secretory granules in them decrease, and the activity of their lysosomal apparatus increases, which is consistent with the often detected patterns of lysosomal destruction of secretory granules - crinophagy. The relative volume occupied by the cells of the terminal sections in large and small glands decreases by 1.5-2 times with aging. Some of the terminal sections atrophy and are replaced by connective tissue, which grows both between the lobules and inside the lobules. Predominantly the protein terminal sections are subject to reduction; mucous sections, on the contrary, increase in volume and accumulate secretions. By the age of 80 (as in early childhood), predominantly mucous cells are found in the parotid gland.
Oncocytes. In the salivary glands of people over 30 years of age, special epithelial cells- oncocytes, which are rarely detected in more at a young age and are present in almost 100% of glands in people over 70 years of age. These cells are found singly or in groups, often in the center of the lobules, both in the terminal sections and in the striated and intercalated ducts. They are characterized by large sizes, sharply oxyphilic granular cytoplasm, a vesicular or pyknotic nucleus (binuclear cells are also found). At the electron microscopic level, a distinctive feature of oncocytes is the presence in their

toplasma huge amount mitochondria, filling most of its volume.
The functional role of oncocytes in the salivary glands, as well as in some other organs (thyroid and parathyroid glands) has not been determined. The traditional view of oncocytes as degeneratively changed elements is not consistent with their ultrastructural characteristics and their active participation in the metabolism of biogenic amines. The origin of these cells is also a matter of debate. According to a number of authors, they arise directly from the cells of the terminal sections and excretory ducts due to their changes. It is also possible that they are formed as a result of a peculiar change in the course of differentiation of the cambial elements of the gland epithelium. Oncocytes of the salivary glands can give rise to special tumors of the organ - oncocytomas.
Excretory ducts. The volume occupied by the striated sections decreases with aging, while the interlobular excretory ducts expand unevenly, and accumulations of compacted material are often found in them. The latter are usually oxyphilic colored, may have a layered structure and contain calcium salts. The formation of such small calcified bodies (calculi) is not considered an indicator of pathological processes in the glands, but the formation of large calculi (with a diameter of several millimeters to several centimeters), causing disturbances in the outflow of saliva, is a leading sign of a disease called salivary stone disease, or sialolithiasis.
The stromal component with aging is characterized by an increase in fiber content (fibrosis). The main changes in this case are due to an increase in volume and a denser arrangement of collagen fibers, but at the same time a thickening of elastic fibers is also observed.
In the interlobular layers, the number of adipocytes increases, which can subsequently appear in the lobules of the glands, replacing the terminal sections. This process is most pronounced in the parotid gland. In the latter, for example, with aging, up to 50% of the terminal sections are replaced by adipose tissue. In places, often along the excretory ducts and subepithelial, accumulations of lymphoid tissue are detected. These processes occur in both large and small salivary glands.

Digestive glands in the oral cavity. Innervation of the salivary glands. Efferent parasympathetic innervation of the submandibular and sublingual glands. Preganglionic fibers come from the nucleus salivatorius superior as part of n. intermedins, then chorda tympani and n. lingualis to the ganglion submandibulare, from where the postganglionic fibers begin, reaching the glands. Efferent parasympathetic innervation of the parotid gland. Preganglionic fibers come from the nucleus salivatorius inferior as part of n. glossopharyngeus, then n. tympanicus, n. petrosus minor to ganglion oticum. This is where the postganglionic fibers begin, going to the gland as part of n. auriculotemporalis. Function: increased secretion of the lacrimal and named salivary glands; dilation of gland vessels. Efferent sympathetic innervation of all these glands. Preganglionic fibers begin in the lateral horns of the upper thoracic segments of the spinal cord and end in the superior cervical ganglion of the sympathetic trunk. Postganglionic fibers begin in the named node and reach the lacrimal gland as part of the plexus caroticus internus, to the parotid gland as part of the plexus caroticus externus, and to the submandibular and sublingual glands through the plexus caroticus externus and then through the plexus facialis. Function: delayed saliva secretion (dry mouth); lacrimation (not a drastic effect).

1. Glandula parotidea (para - near; ous, otos - ear), parotid gland, the largest of the salivary glands, serous type. It is located on the lateral side of the face in front and slightly below the auricle, also penetrating into the fossa retromandibularis. The gland has a lobular structure, covered with fascia, fascia parotidea, which closes the gland into a capsule. The excretory duct of the gland, ductus parotideus, 5-6 cm long, extends from the anterior edge of the gland, runs along the surface of the m. masseter, passing through the fatty tissue of the cheek, pierces the m. buccinator and opens into the vestibule of the mouth with a small opening opposite the second large molar upper jaw. The course of the duct varies extremely. The duct is bifurcated. The parotid gland is a complex alveolar gland in its structure.

2. Glandula submandibularis, submandibular gland, mixed in nature, complex alveolar-tubular in structure, second largest. The gland has a lobular structure. It is located in the fossa submandibularis, extending beyond the posterior edge of m. mylohyoidei. Along the posterior edge of this muscle, the process of the gland is wrapped onto the upper surface of the muscle; an excretory duct, ductus submandibularis, departs from it, which opens onto the caruncula sublingualis.

3. Glandula sublingualis, sublingual gland, mucous type, complex alveolar-tubular in structure. It is located on top of m. mylohyoideus at the bottom of the mouth and forms a fold, plica sublingualis, between the tongue and the inner surface of the lower jaw. The excretory ducts of some lobules (18-20 in number) open independently into the oral cavity along the plica sublingualis (ductus sublinguals minores). Main excretory duct sublingual gland, ductus sublingualis major, runs next to the submandibular duct and opens either with one common opening with it, or immediately nearby.

4. Nutrition of the parotid salivary gland comes from the vessels that perforate it (a. temporalis superficialis); venous blood flows into v. retromandibularis, lymph - in Inn. parotidei; The gland is innervated by the branches of tr. sympathicus and n. glossopharyngeus. Parasympathetic fibers from the glossopharyngeal nerve reach the ganglion oticum and then go to the gland as part of n. auriculotemporalis.

5. The submandibular and sublingual salivary glands feed from a. facialis et lingualis. Venous blood flows into v. facialis, lymph - in Inn. submandibulars et mandibulares. Nerves come from n. intermedius (chorda tympani) and innervate the gland through the ganglion submandibulare.

105- 106. Pharynx - Pharynx, throat, represents that part of the digestive tube and respiratory tract, which is the connecting link between the nasal cavity and mouth, on the one hand, and the esophagus and larynx, on the other. It extends from the base of the skull to the VI-VII cervical vertebrae. The internal space of the pharynx is pharyngeal cavity, cavitas pharyngis. The pharynx is located behind the nasal and oral cavities and larynx, in front of the basilar part of the occipital bone and the upper cervical vertebrae. According to the organs located anterior to the pharynx, it can be divided into three parts: pars nasalis, pars oralis and pars laryngea.

• The upper wall of the pharynx, adjacent to the base of the skull, is called the fornix, fornix pharyngis.
• Pars nasalis pharyngis, the nasal part, is functionally a purely respiratory section. Unlike other parts of the pharynx, its walls do not collapse, as they are motionless.
• The anterior wall of the nasal region is occupied by choanae.
• On the lateral walls there is a funnel-shaped pharyngeal opening of the auditory tube (part of the middle ear), ostium pharyngeum tubae. Above and behind, the opening of the tube is limited by the tubal ridge, torus tubarius, which is obtained as a result of the protrusion of the cartilage of the auditory tube.

At the border between the upper and posterior walls of the pharynx in the midline there is an accumulation of lymphoid tissue, tonsilla pharyngea s. adenoidea (hence - adenoids) (in an adult it is hardly noticeable). Another accumulation of lymphoid tissue, a pair, is located between the pharyngeal opening of the tube and the soft palate, tonsilla tubaria. Thus, at the entrance to the pharynx there is an almost complete ring of lymphoid formations: the tonsil of the tongue, two palatine tonsils, two tubal tonsils and a pharyngeal tonsil (lymphoepithelial ring, described by N. I. Pirogov). Pars oralis, mouth part, is the middle section of the pharynx, which communicates in front through the pharynx, fauces, with the oral cavity; its posterior wall corresponds to the third cervical vertebra. The function of the oral part is mixed, since it is where the digestive and respiratory tracts cross. This cross formed during the development of the respiratory organs from the wall of the primary intestine. From the primary nasal bay, the nasal and oral cavities were formed, and the nasal cavity turned out to be located above or, as it were, dorsal to the oral cavity, and the larynx, trachea and lungs arose from the ventral wall of the foregut. Therefore, the head section of the digestive tract turned out to lie between the nasal cavity (above and dorsally) and the respiratory tract (ventrally), which caused the intersection of the digestive and respiratory tracts in the pharynx.

Pars laryngea, laryngeal part, represents the lower part of the pharynx, located behind the larynx and extending from the entrance to the larynx to the entrance to the esophagus. On the front wall is the entrance to the larynx. The basis of the wall of the pharynx is the fibrous membrane of the pharynx, fascia pharyngobasilaris, which at the top is attached to the bones of the base of the skull, covered on the inside with a mucous membrane, and on the outside with muscle. The muscular layer, in turn, is covered on the outside with a thinner layer of fibrous tissue, which connects the wall of the pharynx with the surrounding organs, and at the top passes to m. buccinator and is called fascia buccopharyngea.

The mucous membrane of the nasal pharynx is covered ciliated epithelium in accordance with the respiratory function of this part of the pharynx, in the lower parts the epithelium is multilayered squamous. Here the mucous membrane acquires a smooth surface that facilitates the sliding of the bolus of food during swallowing. This is also facilitated by the secretion of the mucous glands embedded in it and the muscles of the pharynx, located longitudinally (dilators) and circularly (constrictors).

The circular layer is much more pronounced and splits into three compressors located in 3 floors: upper, m. constrictor pharyngis superior, middle, m. constrictor pharyngis medius and inferior, m. constrictor pharyngis inferior.

Starting at various points: on the bones of the base of the skull (tuberculum pharyngeum of the occipital bone, processus pterygoideus sphenoid), on the lower jaw (linea mylohyoidea), on the root of the tongue, the hyoid bone and the cartilages of the larynx (thyroid and cricoid), the muscle fibers of each side go back and connect with each other, forming a suture along the midline of the pharynx, raphe pharyngis. The lower fibers of the inferior pharyngeal constrictor are closely connected with the muscle fibers of the esophagus. The longitudinal muscle fibers of the pharynx are part of two muscles:

1. M. stylopharyngeus, stylopharyngeus muscle, starts from the processus styloideus, goes down and ends partly in the wall of the pharynx itself, partly attached to the upper edge of the thyroid cartilage.

2. M. palatopharyngeus, velopharyngeal muscle (see Palate).

The act of swallowing. Since the respiratory and digestive tracts cross in the pharynx, there are special devices that separate Airways from digestive. By contracting the muscles of the tongue, the bolus of food is pressed by the back of the tongue against the hard palate and pushed through the pharynx. In this case, the soft palate is pulled upward (abbreviated mm. levator veli palatini and tensor veli palatini) and approaches the posterior wall of the pharynx (abbreviated m. palatopharyngeus).

Thus, the nasal part of the pharynx (respiratory) is completely separated from the oral part. At the same time, the muscles located above the hyoid bone pull the larynx upward, and the root of the tongue by contracting m. hyoglossus descends downwards; it presses on the epiglottis, lowers the latter and thereby closes the entrance to the larynx (airways). Next, a sequential contraction of the pharyngeal constrictors occurs, as a result of which the food bolus is pushed towards the esophagus. The longitudinal muscles of the pharynx function as elevators: they pull the pharynx towards the food bolus.

The nutrition of the pharynx comes mainly from a. pharyngea ascendens and branches of a. facialis and a. maxillaris from a. corotis externa. Venous blood flows into the plexus located on top of the muscular layer of the pharynx, and then along the vv. pharyngeae into system v. jugularis interna. The outflow of lymph occurs in the nodi lymphatici cervicales profundi et retropharyngeales. The pharynx is innervated from the nerve plexus - plexus pharyngeus, formed by the branches of the nn. glossopharyngeus, vagus et tr. sympathicus. In this case, sensitive innervation is also carried out along n. glossopharyngeus and by n. vagus; the muscles of the pharynx are innervated by n. vagus, with the exception of m. stylopharyngeus, which is supplied by n. glossopharyngeus.

107. Esophagus - Esophagus, esophagus, It is a narrow and long active tube inserted between the pharynx and the stomach and helps move food into the stomach. It begins at the level of the VI cervical vertebra, which corresponds to the lower edge of the cricoid cartilage of the larynx, and ends at the level of the XI thoracic vertebra. Since the esophagus, starting in the neck, passes further into the chest cavity and, perforating the diaphragm, enters the abdominal cavity, its parts are distinguished: partes cervicalis, thoracica et abdominalis. The length of the esophagus is 23-25 ​​cm. The total length of the path from the front teeth, including the oral cavity, pharynx and esophagus, is 40-42 cm (at this distance from the teeth, adding 3.5 cm, a gastric rubber probe must be advanced into the esophagus to take gastric juice for examination).

Topography of the esophagus. The cervical part of the esophagus is projected from the VI cervical to the II thoracic vertebra. The trachea lies in front of it, the recurrent nerves and common nerves pass along the side carotid arteries. The syntopy of the thoracic esophagus varies depending on different levels its: the upper third of the thoracic esophagus lies behind and to the left of the trachea, in front of it the left recurrent nerve and left a. carotis communis, behind - the spinal column, on the right - the mediastinal pleura. In the middle third, the aortic arch is adjacent to the esophagus in front and to the left at the level of the IV thoracic vertebra, slightly lower (V thoracic vertebra) - the bifurcation of the trachea and the left bronchus; behind the esophagus lies the thoracic duct; on the left and somewhat posteriorly the descending part of the aorta adjoins the esophagus, on the right - the right nervus vagus, right and back - v. azygos. In the lower third of the thoracic esophagus, behind and to the right of it lies the aorta, in front - the pericardium and the left vagus nerve, on the right - the right vagus nerve, which is shifted below to the posterior surface; v lies somewhat posteriorly. azygos; on the left - the left mediastinal pleura. The abdominal part of the esophagus is covered with peritoneum in front and on the sides; the left lobe of the liver is adjacent to it in front and to the right, the upper pole of the spleen is to the left, and a group of lymph nodes is located at the junction of the esophagus and the stomach.

Structure. On a cross-section, the lumen of the esophagus appears as a transverse slit in the cervical part (due to pressure from the trachea), while in the thoracic part the lumen has a round or stellate shape. The wall of the esophagus consists of the following layers: the innermost - the mucous membrane, tunica mucosa, the middle - tunica muscularis and the outer - connective tissue in nature - tunica adventitia. Tunica mucosa contains mucous glands that facilitate the sliding of food during swallowing with their secretions. When not stretched, the mucous membrane gathers into longitudinal folds. Longitudinal folding is a functional adaptation of the esophagus, facilitating the movement of fluids along the esophagus along the grooves between the folds and stretching the esophagus during the passage of dense lumps of food. This is facilitated by the loose tela submucosa, thanks to which the mucous membrane acquires greater mobility, and its folds easily appear and then smooth out. The layer of unstriated fibers of the mucous membrane itself, lamina muscularis mucosae, also participates in the formation of these folds. The submucosa contains lymphatic follicles. Tunica muscularis, corresponding to the tubular shape of the esophagus, which, when performing its function of carrying food, must expand and contract, is located in two layers - the outer, longitudinal (dilating esophagus), and the internal, circular (constricting). In the upper third of the esophagus, both layers are composed of striated fibers; below they are gradually replaced by non-striated myocytes, so that the muscle layers of the lower half of the esophagus consist almost exclusively of involuntary muscles. Tunica adventitia, surrounding the outside of the esophagus, consists of loose connective tissue through which the esophagus is connected to the surrounding organs. The looseness of this membrane allows the esophagus to change the size of its transverse diameter as food passes through.

Pars abdominalis of the esophagus covered with peritoneum. The esophagus is fed from several sources, and the arteries feeding it form abundant anastomoses among themselves. Ah. esophageae to pars cervicalis of the esophagus come from a. thyroidea inferior. Pars thoracica receives several branches directly from the aorta thoracica, pars abdominalis feeds from the aa. phrenicae inferiores et gastrica sinistra. Venous outflow from the cervical part of the esophagus occurs in v. brachiocephalica, from the thoracic region - in vv. azygos et hemiazygos, from the abdominal - into the tributaries portal vein. From the cervical and upper third of the thoracic esophagus, lymphatic vessels go to the deep cervical nodes, pretracheal and paratracheal, tracheobronchial and posterior mediastinal nodes. From the middle third of the thoracic region, the ascending vessels reach the named nodes chest and neck, and descending (through hiatus esophageus) - nodes abdominal cavity: gastric, pyloric and pancreatoduodenal. Vessels coming from the rest of the esophagus (supradiaphragmatic and abdominal sections) flow into these nodes. The esophagus is innervated from n. vagus et tr. sympathicus. Along the branches of tr. sympathicus conveys the feeling of pain; sympathetic innervation reduces esophageal peristalsis. Parasympathetic innervation enhances peristalsis and gland secretion.