A collection of cells and intercellular substance, similar in origin, structure and functions are called cloth. In the human body they secrete 4 main groups of fabrics: epithelial, connective, muscular, nervous.
Epithelial tissue(epithelium) forms a layer of cells that make up the integument of the body and the mucous membranes of all internal organs and cavities of the body and some glands. Through epithelial tissue, metabolism occurs between the body and environment. In epithelial tissue, cells are very close to each other, there is little intercellular substance.
This creates an obstacle for the penetration of microbes, harmful substances And reliable protection tissues underlying the epithelium. Due to the fact that the epithelium is constantly exposed to various external influences, its cells die in large quantities and are replaced by new ones. Cell replacement occurs due to the ability epithelial cells and fast.
There are several types of epithelium - skin, intestinal, respiratory.
Derivatives of the skin epithelium include nails and hair. The intestinal epithelium is monosyllabic. It also forms glands. These are, for example, the pancreas, liver, salivary glands, sweat glands etc. Enzymes secreted by the glands break down nutrients. Products of the breakdown of nutrients are absorbed by the intestinal epithelium and enter the blood vessels. The respiratory tract is lined with ciliated epithelium. Its cells have outward-facing motile cilia. With their help, particulate matter trapped in the air is removed from the body.
Connective tissue. A feature of connective tissue is the strong development of intercellular substance.
The main functions of connective tissue are nutritional and supporting. Connective tissue includes blood, lymph, cartilage, bone, and adipose tissue. Blood and lymph consist of a liquid intercellular substance and blood cells floating in it. These tissues provide communication between organisms, carrying various gases and substances. Fibrous and connective tissue consists of cells connected to each other by intercellular substance in the form of fibers. The fibers can lie tightly or loosely. Fibrous connective tissue is found in all organs. Adipose tissue also looks like loose tissue. It is rich in cells that are filled with fat.
IN cartilage tissue the cells are large, the intercellular substance is elastic, dense, contains elastic and other fibers. There is a lot of cartilage tissue in the joints, between the vertebral bodies.
Bone consists of bone plates, inside of which lie cells. The cells are connected to each other by numerous thin processes. Bone tissue is hard.
Muscle. This tissue is formed by muscles. Their cytoplasm contains thin filaments capable of contraction. Smooth and striated muscle tissue is distinguished.
The fabric is called cross-striped because its fibers have a transverse striation, which is an alternation of light and dark areas. Smooth muscle tissue is part of the walls of internal organs (stomach, intestines, bladder, blood vessels). Striated muscle tissue is divided into skeletal and cardiac. Skeletal muscle tissue consists of elongated fibers reaching a length of 10–12 cm. Cardiac muscle tissue, like skeletal muscle tissue, has transverse striations. However, unlike skeletal muscle, there are special areas where the muscle fibers close tightly together. Thanks to this structure, the contraction of one fiber is quickly transmitted to neighboring ones. This ensures simultaneous contraction of large areas of the heart muscle. Muscle contraction has great value. The contraction of skeletal muscles ensures the movement of the body in space and the movement of some parts in relation to others. Due to smooth muscles, internal organs contract and the diameter of blood vessels changes.
Nervous tissue. Structural unit nervous tissue is a nerve cell - a neuron.
A neuron consists of a body and processes. The neuron body can be various shapes– oval, star-shaped, polygonal. A neuron has one nucleus, usually located in the center of the cell. Most neurons have short, thick, strongly branching processes near the body and long (up to 1.5 m), thin, and branching processes only at the very end. Long processes of nerve cells form nerve fibers. The main properties of a neuron are the ability to be excited and the ability to conduct this excitation along nerve fibers. In nervous tissue these properties are especially well expressed, although they are also characteristic of muscles and glands. Excitation is transmitted along the neuron and can be transmitted to other neurons or muscles connected to it, causing it to contract. The importance of the nervous tissue that forms the nervous system is enormous. Nervous tissue not only forms part of the body as part of it, but also ensures the unification of the functions of all other parts of the body.
Tissue as a collection of cells and intercellular substance. Types and types of fabrics, their properties. Intercellular interactions.
There are about 200 types of cells in the adult human body. Groups of cells that have the same or similar structure, are connected by a common origin and are adapted to perform certain functions form fabrics . This is the next level of the hierarchical structure of the human body - the transition from the cellular level to the tissue level (see Figure 1.3.2).
Any tissue is a collection of cells and intercellular substance , which can be a lot (blood, lymph, loose connective tissue) or little (integumentary epithelium).
The cells of each tissue (and some organs) have their own name: the cells of the nervous tissue are called neurons , cells bone tissue - osteocytes , liver - hepatocytes and so on.
Intercellular substance chemically is a system consisting of biopolymers in high concentration and water molecules. It contains structural elements: collagen fibers, elastin, blood and lymph capillaries, nerve fibers and sensory endings (pain, temperature and other receptors). This provides the necessary conditions for the normal functioning of tissues and the performance of their functions.
There are four types of fabrics in total: epithelial , connecting (including blood and lymph), muscular And nervous (see figure 1.5.1).
Epithelial tissue , or epithelium , covers the body, lines the internal surfaces of organs (stomach, intestines, Bladder and others) and cavities (abdominal, pleural), and also forms the majority of glands. In accordance with this, a distinction is made between the integumentary and glandular epithelium.
Covering epithelium (type A in Figure 1.5.1) forms layers of cells (1), closely - practically without intercellular substance - adjacent to each other. It happens single-layer or multilayer . The integumentary epithelium is a border tissue and performs the main functions: protection from external influences and participation in the metabolism of the body with the environment - absorption of food components and release of metabolic products ( excretion ). The integumentary epithelium is flexible, ensuring the mobility of internal organs (for example, contractions of the heart, distension of the stomach, intestinal motility, expansion of the lungs, and so on).
Glandular epithelium consists of cells, inside of which there are granules with a secret (from the Latin secretio- department). These cells synthesize and secrete many substances important to the body. Through secretion, saliva, gastric and intestinal juices, bile, milk, hormones and other biologically active compounds are formed. The glandular epithelium can form independent organs - glands (for example, the pancreas, thyroid, endocrine glands, or endocrine glands , releasing hormones directly into the blood that perform regulatory functions in the body and others), and may be part of other organs (for example, gastric glands).
Connective tissue (types B and C in Figure 1.5.1) is distinguished by a wide variety of cells (1) and an abundance of intercellular substrate, consisting of fibers (2) and amorphous substance (3). Fibrous connective tissue can be loose or dense. Loose connective tissue (type B) is present in all organs, it surrounds the blood vessels and lymphatic vessels. Dense connective tissue performs mechanical, supporting, shaping and protective functions. In addition, there is also very dense connective tissue (type B), which consists of tendons and fibrous membranes (hard meninges, periosteum and others). Connective tissue not only performs mechanical functions, but also actively participates in metabolism, the production of immune bodies, the processes of regeneration and wound healing, and ensures adaptation to changing living conditions.
Connective tissue also includes adipose tissue (View D in Figure 1.5.1). Fats are deposited (deposited) in it, the breakdown of which releases a large amount of energy.
Play an important role in the body skeletal (cartilage and bone) connective tissues . They perform mainly supporting, mechanical and protective functions.
Cartilage tissue (type D) consists of cells (1) and a large amount of elastic intercellular substance (2), it forms intervertebral discs, some components of the joints, trachea, bronchi. Cartilage tissue does not have blood vessels and receives the necessary substances by absorbing them from surrounding tissues.
Bone (type E) consists of bone plates, inside of which lie cells. The cells are connected to each other by numerous processes. Bone tissue is hard and the bones of the skeleton are built from this tissue.
A type of connective tissue is blood . In our minds, blood is something very important for the body and, at the same time, difficult to understand. Blood (type G in Figure 1.5.1) consists of intercellular substance - plasma (1) and weighed in it shaped elements (2) - red blood cells, leukocytes, platelets (Figure 1.5.2 shows their photographs obtained using electron microscope). All shaped elements develop from a common precursor cell. The properties and functions of blood are discussed in more detail in section 1.5.2.3.
Cells muscle tissue (Figure 1.3.1 and types Z and I in Figure 1.5.1) have the ability to contract. Since contraction requires a lot of energy, muscle cells have a higher content mitochondria .
There are two main types of muscle tissue - smooth (type 3 in Figure 1.5.1), which is present in the walls of many, and usually hollow, internal organs (vessels, intestines, gland ducts and others), and striated (view I in Figure 1.5.1), which includes cardiac and skeletal muscle tissue. Bundles of muscle tissue form muscles. They are surrounded by layers of connective tissue and penetrated by nerves, blood and lymphatic vessels (see Figure 1.3.1).
General information on tissues is given in Table 1.5.1.
Table 1.5.1. Tissues, their structure and functions
| Fabric name | Specific cell names | Intercellular substance | Where is it found? this fabric | Functions | Drawing |
|---|---|---|---|---|---|
| EPITHELIAL TISSUE | |||||
| Covering epithelium (single-layer and multilayer) | Cells ( epithelial cells ) fit tightly to each other, forming layers. The cells of the ciliated epithelium have cilia, while the cells of the intestinal epithelium have villi. | Small, does not contain blood vessels; the basement membrane demarcates the epithelium from the underlying connective tissue. | The internal surfaces of all hollow organs (stomach, intestines, bladder, bronchi, blood vessels, etc.), cavities (abdominal, pleural, articular), the surface layer of skin ( epidermis ). | Protection from external influences (epidermis, ciliated epithelium), absorption of food components (gastrointestinal tract), excretion of metabolic products (urinary system); ensures organ mobility. | Fig.1.5.1, view A |
| Glandular epithelium |
Glandulocytes contain secretory granules with biologically active substances. They can be located singly or form independent organs (glands). | The intercellular substance of the gland tissue contains blood, lymphatic vessels, and nerve endings. | Glands of internal (thyroid, adrenal glands) or external (salivary, sweat) secretion. Cells can be located singly in cover epithelium (respiratory system, gastrointestinal tract). | Output hormones (section 1.5.2.9), digestive enzymes (bile, gastric, intestinal, pancreatic juice, etc.), milk, saliva, sweat and tear fluid, bronchial secretions, etc. | Rice. 1.5.10 “Skin structure” - sweat and sebaceous glands |
| Connective tissues | |||||
| Loose connective | The cellular composition is characterized by great diversity: fibroblasts , fibrocytes , macrophages , lymphocytes , single adipocytes and etc. | A large number of; consists of an amorphous substance and fibers (elastin, collagen, etc.) | Present in all organs, including muscles, surrounds blood and lymphatic vessels, nerves; main component dermis . | Mechanical (sheath of vessel, nerve, organ); participation in metabolism ( trophism ), the production of immune bodies, processes regeneration . | Fig.1.5.1, view B |
| Dense connecting | Fibers predominate over amorphous matter. | Framework of internal organs, dura mater, periosteum, tendons and ligaments. | Mechanical, shaping, supporting, protective. | Fig.1.5.1, view B | |
| Fat | Almost the entire cytoplasm adipocytes occupies a fat vacuole. | There is more intercellular substance than cells. | Subcutaneous fatty tissue, perinephric tissue, omentums abdominal cavity etc. | Deposition of fats; energy supply due to the breakdown of fats; mechanical. | Fig.1.5.1, view D |
| Cartilaginous | Chondrocytes , chondroblasts (from lat. chondron- cartilage) | It is distinguished by its elasticity, including due to its chemical composition. | Cartilages of the nose, ears, larynx; articular surfaces of bones; anterior ribs; bronchi, trachea, etc. | Supportive, protective, mechanical. Participates in mineral metabolism (“salt deposition”). Bones contain calcium and phosphorus (almost 98% of total number calcium!). | Fig.1.5.1, view D |
| Bone | Osteoblasts , osteocytes , osteoclasts (from lat. os- bone) | Strength is due to mineral “impregnation”. | Skeletal bones; auditory ossicles V tympanic cavity(hammer, incus and stapes) | Fig.1.5.1, view E | |
| Blood | Red blood cells (including juvenile forms), leukocytes , lymphocytes , platelets and etc. | Plasma 90-93% consists of water, 7-10% - proteins, salts, glucose, etc. | Internal contents of the cavities of the heart and blood vessels. If their integrity is violated, bleeding and hemorrhage occur. | Gas exchange, participation in humoral regulation, metabolism, thermoregulation, immune defense; coagulation as a defensive reaction. | Fig.1.5.1, view G; Fig.1.5.2 |
| Lymph | Mostly lymphocytes | Plasma (lymphoplasma) | Internal contents of the lymphatic system | Participation in immune defense, metabolism, etc. | Rice. 1.3.4 "Cell Shapes" |
| MUSCLE TISSUE | |||||
| Smooth muscle tissue | Orderly arranged myocytes spindle-shaped | There is little intercellular substance; contains blood and lymphatic vessels, nerve fibers and endings. | In the walls of hollow organs (vessels, stomach, intestines, urinary and gall bladder, etc.) | Peristalsis gastrointestinal tract, bladder contraction, maintenance blood pressure due to vascular tone, etc. | Fig.1.5.1, view 3 |
| Cross-striped | Muscle fibers can contain over 100 cores! | Skeletal muscles; cardiac muscle tissue is automatic (chapter 2.6) | Pumping function of the heart; voluntary muscle activity; participation in thermoregulation of the functions of organs and systems. | Fig.1.5.1 (view I) | |
| NERVOUS TISSUE | |||||
| Nervous | Neurons ; neuroglial cells perform auxiliary functions | Neuroglia rich in lipids (fats) | Brain and spinal cord, ganglia ( ganglia), nerves ( nerve bundles, plexuses, etc.) | Perception of irritation, generation and conduction of impulses, excitability; regulation of the functions of organs and systems. | Fig.1.5.1, view K |
The preservation of shape and the performance of specific functions by the tissue is genetically programmed: the ability to perform specific functions and to differentiate is transmitted to daughter cells via DNA. The regulation of gene expression as the basis of differentiation was discussed in section 1.3.4.
Differentiation is a biochemical process in which relatively homogeneous cells, arising from a common progenitor cell, are transformed into increasingly specialized, specific types of cells that form tissues or organs. Most differentiated cells usually retain their specific signs even in new surroundings.
In 1952, scientists from the University of Chicago separated chicken embryo cells by growing (incubating) them in an enzyme solution with gentle stirring. However, the cells did not remain separated, but began to unite into new colonies. Moreover, when liver cells mixed with retinal cells, the formation of cellular aggregates occurred in such a way that the retinal cells always moved to the inner part of the cell mass.
Cell interactions . What allows fabrics not to crumble at the slightest external influence? And what ensures the coordinated work of cells and their performance of specific functions?
Many observations prove that cells have the ability to recognize each other and respond accordingly. Interaction is not only the ability to transmit signals from one cell to another, but also the ability to act together, that is, synchronously. On the surface of each cell there are receptors (see section 1.3.2), thanks to which each cell recognizes another similar to itself. And these “detector devices” function according to the “key-lock” rule - this mechanism is repeatedly mentioned in the book.
Let's talk a little about how cells communicate with each other. There are two main methods of intercellular interaction: diffusion And adhesive . Diffusion is an interaction based on intercellular channels, pores in the membranes of neighboring cells located strictly opposite each other. Adhesive (from Latin adhaesio- adhesion, adhesion) - mechanical connection of cells, long-term and stable holding them at a close distance from each other. The chapter on cell structure describes different kinds intercellular connections (desmosomes, synapses and others). This is the basis for the organization of cells into various multicellular structures (tissues, organs).
Each tissue cell not only connects with neighboring cells, but also interacts with the intercellular substance, receiving with its help nutrients, signaling molecules (hormones, mediators), and so on. Through chemical substances delivered to all tissues and organs of the body is carried out humoral type of regulation (from Latin humor- liquid).
Another way of regulation, as mentioned above, is carried out using the nervous system. Nerve impulses always reach their target hundreds or thousands of times faster than delivery of chemicals to organs or tissues. The nervous and humoral ways of regulating the functions of organs and systems are closely interrelated. However, the very formation of most chemicals and their release into the blood are under constant control of the nervous system.
Cell, fabric - these are the first levels of organization of living organisms , but even at these stages it is possible to distinguish general mechanisms regulations that ensure the vital functions of organs, organ systems and the body as a whole.
Different cells make up different tissues. The entire variety of tissues of multicellular animals is usually divided into 4 groups:
Epithelium is a layer that covers the internal and external surfaces of organisms. Its main function is to protect the relevant organs from mechanical damage and infection. In those places where body tissue is subjected to constant stress and friction and “wears out,” epithelial cells multiply at high speed. Often, in areas of high stress, the epithelium becomes denser or keratinized. The free surface of the epithelium can also perform the functions of absorption, secretion and excretion, and perceive irritations.
Epithelial tissue- consist of cells closely adjacent to each other, located in one or several layers. The main role of these tissues is to provide cover, protection, excretory functions and the perception of external and internal irritations. The composition of epithelial tissues includes:
1. Epidermis - the epithelium that forms the outer covering of the body - it is a stratified squamous epithelium;
2. The epithelium that lines the tubular formations of the body from the inside is a single-layer cylindrical epithelium of most of the gastrointestinal tract, a single-layer or stratified glandular epithelium and a single-layer ciliated epithelium of the respiratory tract;
3. The mesothelium gives rise to the covering of serous membranes such as the peritoneum, pleura and pericardium and consists of a single layer of flat cells;
4. The endothelium lines the inner surface of blood and lymphatic vessels and consists of a single layer of flat cells;
5. Ependymal epithelium, which lines the meninges in the form of a single layer of flat cells.
Epithelial cells are held together by a cementitious substance containing hyaluronic acid. Since the epithelium does not have blood vessels, oxygen supply and nutrients occurs by diffusion through lymphatic system. Nerve endings can penetrate the epithelium.
Connective tissues are characterized by the presence of a large amount of intercellular substance, which, depending on the role of the tissue, can be liquid, gelatinous, fibrous and impregnated with calcium salts.
Common features of connective tissues are:
- the cells are sufficiently distant from each other;
- intercellular spaces are highly developed, filled with intercellular substance, which is produced by the cells themselves. The intercellular substance can have different consistencies (liquid and solid), different fibers (collagen, elastic). The nature of the intercellular substance is its chemical composition, structure and physical properties determine the functions performed by a specific type of connective tissue.
Connective tissues include blood, lymph, cartilage, bone, fat, and loose connective tissue.
Bone tissue is part of the bones. It has special mechanical properties: hardness, strength due to the special composition of the intercellular substance. The intercellular substance consists of mineral salts, mainly calcium and phosphorus salts (70%) and organic matter - the proteins ossein and collagen (30%). Bone tissue cells - osteocytes, osteoblasts, osteoclasts. Osteocytes are mature bone cells. Osteoblasts are young bone cells, due to which bones grow in thickness and length. Osteoclasts are bone-destroying cells involved in bone remodeling. The intercellular substance forms bone plates with a thickness of 4 to 15 microns. The structural and functional unit of bone tissue is the osteon. An osteon is a system of concentric cylindrical bone plates inserted into each other. Between the laminae of the osteon are bone cells. Inside, along the osteon lies a canal (Haversian canal), in which small blood vessels pass. In bones, osteons are oriented in the direction of the greatest loads, so the osteon structure gives the bones additional strength. Intercalated bone plates are located between the osteons.
Cartilage tissue consists of mature cartilage cells - chondrocytes and young cartilage cells - chondroblasts. The intercellular substance contains a large number of elastic and collagen fibers and others organic matter. There are three types of cartilage tissue: hyaline, elastic and fibrous cartilage.
The connective tissue itself has a special structure of intercellular substance. It is represented by a gel-like mass in which thin fibers lie in different directions in the form of a network. Loose fibrous connective tissue covers blood and lymphatic vessels, nerves, and is part of the skin. Dense fibrous connective tissue is characterized by a strong development of fibers that lie more orderly than in loose tissue. Forms periosteum, tendons, ligaments.
Adipose tissue consists of fat cells in which droplets of fat accumulate. Performs storage, depositing, heat-insulating, shock-absorbing functions. Mainly developed in the deep layer of the skin, deposited on the surface of internal organs. It is divided into two types: white adipose tissue and brown adipose tissue. In humans, white adipose tissue predominates. Brown adipose tissue is well developed in newborns; it mainly performs the function of heat production to warm the body.
Blood and lymph are liquid connective tissues, the basis of their intercellular substance is water. Blood and lymph cells are called formed elements. There are three groups of cells in the blood that have a specific structure and function: erythrocytes, leukocytes and platelets. In lymph, the main cells are a special type of leukocyte - lymphocytes. These fabrics are included internal environment the human body and perform the main function - transport.
Functions of connective tissues:
Support-mechanical
Trophic (nutritional) in relation to other tissues
Protective (mechanical protection, phagocytosis, immunity)
Structure-forming (plastic; participates in wound healing, healing of bone fractures and other processes associated with changes in the structure of organs)
Transport (connective tissues transport nutrients, metabolites, gases, end products of metabolism, regulatory substances)
Muscle tissue characterized by a pronounced ability to contract in response to irritation. These include striated skeletal, striated cardiac and smooth muscle tissue. Muscle tissue cells are mono- or multinucleated formations that have an elongated shape and are called symplasts or muscle fibers.
Cells of many tissues have the ability to change shape, but in muscle tissue this ability becomes the main function.
Basic morphological characteristics elements of muscle tissue: elongated shape, the presence of longitudinally located myofibrils and myofilaments - special organelles that ensure contractility, the location of mitochondria next to the contractile elements, the presence of inclusions of glycogen, lipids and myoglobin.
Special contractile organelles - myofilaments or myofibrils - provide contraction, which occurs when two main fibrillar proteins interact in them - actin and myosin - with the obligatory participation of calcium ions. Mitochondria provide energy for these processes. The reserve of energy sources is formed by glycogen and lipids. Myoglobin is a protein that ensures the binding of oxygen and the creation of its reserve at the time of muscle contraction, when the blood vessels are compressed (the oxygen supply drops sharply).
Nervous tissue capable of perceiving irritations, transforming them into excitement and transmitting it to various organs or other parts of the nervous tissue. They consist of nerve cells (neurons) of various shapes and sizes with characteristic processes and special interstitial tissue (neuroglia), which provides support and trophic functions in relation to neurons.
Nervous tissue consists of nerve cells (neurons) and neuroglia, which perform supporting, protective and delimiting functions. Nerve cells and neuroglia form a morphologically and functionally unified nervous system. The nervous system establishes the relationship between the body and the external environment and participates in the coordination of functions within the body, ensuring its integrity. The structural and functional unit of nervous tissue is the nerve cell (neuron, neurocyte). A neuron consists of a body and processes of varying lengths. One long, non-branching process is called an axon. The axon carries the nerve impulse away from the body nerve cell to working organs or to another nerve cell. Other processes (one or more) - short, branched - are called dendrites. Their endings perceive stimuli and conduct nerve impulses to the body of the neuron. Depending on the function performed, they are distinguished: sensory (afferent), intercalary (associative) and motor (efferent) nerve cells.
The nerve processes, covered with a sheath, form nerve fibers that form into bundles that form nerves. Nerve fibers are divided by function into sensory and motor. Neurons connect to each other using synapses (contacts). Synapses transmit or delay nerve impulses; they are also present in places where the receptor endings of neuron processes come into contact with organs. Neuroglial cells (astrocytes and olegodendrocytes) form the supporting apparatus of the central nervous system, surround the bodies of neurons and their processes, and line the cavities of the brain and spinal cord.
Functions of nervous tissue:
Perception of irritation
Generation of a nerve impulse
Conducting excitation
Signal Analysis
Formation of a response
In any living or plant organism, tissue is formed by cells similar in origin and structure. Any tissue is adapted to perform one or several important functions for an animal or plant organism.
Types of tissues in higher plants
The following types of plant tissues are distinguished:
- educational (meristem);
- integumentary;
- mechanical;
- conductive;
- basic;
- excretory.
All these tissues have their own structural features and differ from each other in the functions they perform.
Fig.1 Plant tissue under a microscope
Educational plant tissue
Educational fabric- This is the primary tissue from which all other plant tissues are formed. It consists of special cells capable of multiple divisions. It is these cells that make up the embryo of any plant.
This tissue is retained in the adult plant. It is located:
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- at the bottom of the root system and at the tops of the stems (ensures plant growth in height and development of the root system) - apical educational tissue;
- inside the stem (ensures the plant grows in width and thickens) - lateral educational tissue;
Plant integumentary tissue
Covering tissue is a protective tissue. It is necessary in order to protect the plant from sharp changes temperature, from excessive evaporation of water, from microbes, fungi, animals and from all kinds of mechanical damage.
The integumentary tissues of plants are formed by cells, living and dead, that are capable of allowing air to pass through, providing the gas exchange necessary for plant growth.
The structure of plant integumentary tissue is as follows:
- first there is the skin or epidermis, which covers the leaves of the plant, stems and the most vulnerable parts of the flower; skin cells are living, elastic, they protect the plant from excessive moisture loss;
- Next is the cork or periderm, which is also located on the stems and roots of the plant (where the cork layer is formed, the skin dies); The cork protects the plant from adverse environmental influences.
There is also a type of integumentary tissue known as crust. This is the strongest covering fabric, cork in in this case is formed not only on the surface, but also in depth, and its upper layers slowly die off. Essentially, the crust is made up of cork and dead tissue.
Fig. 2 Crust - a type of plant covering tissue
For the plant to breathe, cracks form in the crust, at the bottom of which there are special shoots, lentils, through which gas exchange occurs.
Mechanical plant tissue
Mechanical tissues give the plant the strength it needs. It is thanks to their presence that the plant can withstand strong gusts of wind and do not break under streams of rain or under the weight of fruits.
There are two main types of mechanical fabrics: bast and wood fibers.
Conductive plant tissues
Conductive fabric ensures the transport of water with minerals dissolved in it.
This tissue forms two transport systems:
- upward(from roots to leaves);
- downward(from leaves to all other parts of plants).
The ascending transport system consists of tracheids and vessels (xylem or wood), and vessels are more advanced conductors than tracheids.
In descending systems, the flow of water with photosynthesis products passes through sieve tubes (phloem or phloem).
Xylem and phloem form vascular-fibrous bundles - “ circulatory system"plant, which permeates it completely, connecting it into one whole.
Main fabric
Ground tissue or parenchyma- is the basis of the entire plant. All other types of fabrics are immersed in it. This is living tissue and it performs different functions. It is because of this that its different types are distinguished (information about the structure and functions different types main fabric is presented in the table below).
| Types of main fabric | Where is it located in the plant? | Functions | Structure |
| Assimilation | leaves and other green parts of the plant | promotes the synthesis of organic substances | consists of photosynthetic cells |
| Storage | tubers, fruits, buds, seeds, bulbs, root vegetables | promotes the accumulation of organic substances necessary for plant development | thin-walled cells |
| Aquifer | stem, leaves | promotes water accumulation | loose tissue consisting of thin-walled cells |
| Airborne | stem, leaves, roots | promotes air circulation throughout the plant | thin-walled cells |
Rice. 3 The main tissue or parenchyma of the plant
Excretory tissues
The name of this fabric indicates exactly what function it plays. These fabrics help saturate the fruits of plants with oils and juices, and also contribute to the release of a special aroma by the leaves, flowers and fruits. Thus, there are two types of this fabric:
- endocrine tissue;
- Exocrine tissue.
What have we learned?
For the biology lesson, 6th grade students need to remember that animals and plants consist of many cells, which, in turn, arranged in an orderly manner, form one or another tissue. We found out what types of tissues exist in plants - educational, integumentary, mechanical, conductive, basic and excretory. Each tissue performs its own strictly defined function, protecting the plant or providing all its parts with access to water or air.
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The body of many living organisms consists of tissues. Exceptions are all unicellular organisms, as well as some multicellular organisms, for example, which include algae and lichens. In this article we will look at the types of fabrics. Biology studies this topic, namely its section - histology. The name of this industry comes from Greek words"fabric" and "knowledge". There are many types of fabrics. Biology studies both plants and animals. They have significant differences. Biology has been studied for quite some time. For the first time they were described even by such ancient scientists as Aristotle and Avicenna. Biology continues to study tissues and types of tissues - in the 19th century they were studied by such famous scientists as Moldenhauer, Mirbel, Hartig and others. With their participation, new types of cell aggregates were discovered and their functions were studied.
Types of tissues - biology
First of all, it should be noted that the tissues that are characteristic of plants are not characteristic of animals. Therefore, biology can divide tissue types into two large groups: plant and animal. Both combine a large number of varieties. We will consider them further.
Types of animal tissues
Let's start with what is closer to us. Since we belong to the animal kingdom, our body consists precisely of tissues, the varieties of which will now be described. Types of animal tissues can be grouped into four large groups: epithelial, muscle, connective and nervous. The first three are divided into many varieties. Only the last group is represented by only one type. Next, we will consider all types of tissues, the structure and functions that are characteristic of them, in order.
Nervous tissue
Since it only comes in one variety, let's start with that one. The cells of this tissue are called neurons. Each of them consists of a body, an axon and dendrites. The latter are processes through which an electrical impulse is transmitted from cell to cell. A neuron has one axon - it is a long process, there are several dendrites, they are smaller than the first one. The cell body contains the nucleus. In addition, the cytoplasm contains the so-called Nissl bodies - an analogue of the endoplasmic reticullum, mitochondria, which produce energy, as well as neurotubules, which are involved in conducting impulses from one cell to another.
Depending on their functions, neurons are divided into several types. The first type is sensory, or afferent. They conduct impulses from the sense organs to the brain. The second type of neurons is associative, or switching. They analyze the information received from the senses and develop a response impulse. These types of neurons are found in the brain and spinal cord. The last type is motor, or afferent. They conduct impulses from association neurons to the organs. Nervous tissue also contains intercellular substance. It performs very important functions, namely, it ensures a fixed location of neurons in space, and is involved in the removal of unnecessary substances from the cell.
Epithelial
These are types of tissues whose cells are tightly adjacent to each other. They can have a variety of shapes, but are always located close. All the different types of tissues in this group are similar in that they have little intercellular substance. It is mainly presented in the form of a liquid, in some cases it may not be present. These are the types of body tissues that provide its protection and also perform secretory function.
This group includes several varieties. These are flat, cylindrical, cubic, sensory, ciliated and glandular epithelium. From the name of each one you can understand what form of cells they are made of. Various types epithelial tissue They also differ in their location in the body. Thus, the flat one lines the cavities of the upper organs of the digestive tract - oral cavity and esophagus. Columnar epithelium is found in the stomach and intestines. Cubic can be found in the renal tubules. The sensory one lines the nasal cavity; it contains special villi that provide the perception of odors. Ciliated epithelial cells, as its name implies, have cytoplasmic cilia. This type of fabric lines Airways, which are located below the nasal cavity. The cilia that each cell has perform a cleansing function - they to some extent filter the air that passes through the organs covered by this type of epithelium. And the last type of this group of tissues is glandular epithelium. Its cells perform a secretory function. They are found in the glands, as well as in the cavities of some organs, such as the stomach. Cells of this type of epithelium produce hormones, gastric juice, milk, sebum and many other substances.
Muscle tissue
This group is divided into three types. The muscle is smooth, striated and cardiac. All muscle tissues are similar in that they consist of long cells - fibers; they contain a very large number of mitochondria, since they need a lot of energy to carry out movements. lines the cavities of internal organs. We cannot control the contraction of such muscles ourselves, since they are innervated by the autonomic nervous system.
Cells of striated muscle tissue are distinguished by the fact that they contain more mitochondria than the first. This is because they require more energy. Striated muscles can contract much faster than smooth muscles. It consists of skeletal muscles. They are innervated by the somatic nervous system, so we can consciously control them. Cardiac muscle tissue combines some of the characteristics of the first two. It is capable of contracting as actively and quickly as the striated one, but is innervated by the autonomic nervous system, just like the smooth one.
Connective tissue types and their functions
All tissues of this group are characterized by a large amount of intercellular substance. In some cases it appears in a liquid aggregate state, in some - in a liquid state, sometimes - in the form of an amorphous mass. Seven types belong to this group. These are dense and loose fibrous, bone, cartilage, reticular, fatty, blood. The first type is dominated by fibers. It is located around the internal organs. Its functions are to give them elasticity and protect them. In loose fibrous tissue, the amorphous mass predominates over the fibers themselves. It completely fills the gaps between internal organs, while dense fibrous forms only peculiar shells around the latter. She also plays a protective role.
Bone and form the skeleton. It performs a supporting and partly protective function in the body. In the cells and intercellular substance of bone tissue, phosphates and calcium compounds predominate. The exchange of these substances between the skeleton and blood is regulated by hormones such as calcitonin and parathyrotropin. The first maintains the normal condition of bones by participating in the conversion of phosphorus and calcium ions into organic compounds, stored in the skeleton. And the second, on the contrary, with a lack of these ions in the blood provokes their production from skeletal tissues.
Blood contains a lot of liquid intercellular substance, it is called plasma. Its cells are quite peculiar. They are divided into three types: platelets, erythrocytes and leukocytes. The former are responsible for blood clotting. During this process, a small blood clot is formed, which prevents further blood loss. Red blood cells are responsible for transporting oxygen throughout the body and providing it to all tissues and organs. They may contain aglutinogens, which exist in two types - A and B. Blood plasma may contain alpha or beta aglutinins. They are antibodies to aglutinogens. These substances are used to determine the blood type. In the first group, no aglutinogens are observed on the erythrocytes, and in the plasma there are two types of aglutinins at once. The second group has aglutinogen A and aglutinin beta. The third is B and alpha. There are no aglutinins in the plasma of the fourth, but aglutinogens A and B are present on the red blood cells. If A meets alpha or B meets beta, the so-called aglutination reaction occurs, as a result of which the red blood cells die and blood clots form. This can happen if you transfuse blood of the wrong type. Considering that only red blood cells are used during transfusion (plasma is screened out at one of the processing stages donated blood), then a person with the first group can only be transfused with blood of his own group, with the second - blood of the first and second groups, with the third - with the first and third groups, with the fourth - with any group.
Also, D antigens may be present on red blood cells, which determines the Rh factor; if they are present, the latter is positive; if absent, it is negative. Lymphocytes are responsible for immunity. They are divided into two main groups: B lymphocytes and T lymphocytes. The former are produced in the bone marrow, the latter - in the thymus (gland located behind the sternum). T lymphocytes are divided into T-inducers, T-helpers and T-suppressors. Reticular connective tissue consists of a large amount of intercellular substance and stem cells. Blood cells are formed from them. This fabric forms the basis bone marrow and other hematopoietic organs. There are also cells that contain lipids. It performs a reserve, thermal insulation and sometimes protective function.
How do plants work?
These organisms, like animals, consist of aggregates of cells and intercellular substance. We will describe the types of plant tissues further. All of them are divided into several large groups. These are educational, integumentary, conductive, mechanical and basic. The types of plant tissues are numerous, as several belong to each group.
Educational
These include apical, lateral, insertional and wound. Their main function is to ensure plant growth. They consist of small cells that actively divide and then differentiate to form any other type of tissue. The apical ones are located at the tips of the stems and roots, the lateral ones - inside the stem, under the integumentary ones, the intercalary ones - at the bases of the internodes, the wound ones - at the site of damage.
Integumentary
They are characterized by thick cell walls composed of cellulose. They play a protective role. There are three types: epidermis, crust, plug. The first covers all parts of the plant. It may have a protective waxy coating; it also contains hairs, stomata, cuticle, and pores. The crust is distinguished by the fact that it does not have pores; in all other characteristics it is similar to the epidermis. Cork is dead integumentary tissues, which form the bark of trees.
Conductive
These tissues come in two varieties: xylem and phloem. Their functions are the transport of substances dissolved in water from the root to other organs and vice versa. Xylem is formed from vessels formed by dead cells with hard shells; there are no transverse membranes. They transport liquid upward.
Phloem - sieve tubes - living cells that do not have nuclei. The transverse membranes have large pores. With the help of this type of plant tissue, substances dissolved in water are transported downward.
Mechanical
They also come in two types: and sclerenchyma. Their main task is to ensure the strength of all organs. Collenchyma is represented by living cells with lignified membranes that fit tightly to each other. Sclerenchyma consists of elongated dead cells with hard membranes.
Basic
As their name implies, they form the basis of all plant organs. They are assimilation and spare. The first are found in the leaves and green part of the stem. Their cells contain chloroplasts, which are responsible for photosynthesis. Organic substances accumulate in the storage tissue, in most cases it is starch.
