The material is taken from the site www.hystology.ru

The organs of the oral cavity are mostly covered with a mucous membrane. It is attached to the bone base of the upper and lower jaws and has a well-defined epithelial layer and a basal lamina. The muscular plate is absent, the submucosa is present only in the cheek area. The epithelial layer is represented by stratified squamous (squamous) epithelium. The basal lamina is made up of fibrous connective tissue.

Lips perform mechanical and tactile functions. These are skin folds in which the outer and inner surfaces are distinguished.

The outer surface of the lip consists of fibrous connective tissue, covered, like the skin, with stratified squamous keratinized epithelium. The skin surface of the upper lip in ruminants passes into the nasal mirror, and in pigs - into the snout. The outer surface of the lip contains hair, sebaceous and sweat glands.

The inner surface of the lip is covered with a mucous membrane. The squamous stratified keratinizing epithelium is located on the main plate, which, in the form of high outgrowths - papillae, protrudes into the epithelium, contributing to an increase in the surface of contact with the epithelium and improving its nutrition.

The muscular layer of the mucous membrane is absent. The main plate passes into the submucosa, where the terminal sections of the complex tubular-alveolar salivary glands are located. By the nature of the produced secret, they are serous and mucous. The excretory ducts open to the surface of the epithelium.

The basis of the lips is the striated muscle tissue of the circular muscle.

The lips are abundantly innervated. They have many different types of receptors and a dense capillary network.

Cheeks consist of inner, middle and outer shells. The inner shell is a mucous membrane that passes to other organs of the oral cavity. It is lined with squamous stratified keratinized epithelium. The main plate forms high papillae covered with keratinized epithelial cells. The middle shell is built from striated muscle fibers and salivary buccal glands located in the connective tissue. The outer shell consists of skin with hair, sebaceous and sweat glands.

Sky is hard and soft.

The hard palate fuses with the periosteum of the bony palate. Its mucous membrane is built from intensely keratinizing stratified squamous epithelium and the main plate containing a network of thin-walled veins that can swell. In a horse, this network looks like a cavernous body. There is no submucosa.

The soft palate, or palatine curtain, is a fold of mucous membrane that separates the oral cavity from the pharynx. The mucous membrane directed into the oral cavity is covered with stratified squamous keratinized epithelium. The main plate forms numerous papillae. In the submucosal base lie the terminal sections of the mucous glands and palatine tonsils (lymph nodules). The basis of the soft palate is represented by striated muscle tissue. The surface of the soft palate, facing the pharynx, is covered with a single layer of multi-row ciliated epithelium. There are no papillae, there are fewer glands in the submucosa. They are

Rice. 232.

Longitudinal section of a ruminant incisor (BUT) and horses (B):
a- crown; b - neck; c - root; g - tooth cavity; d- dentin; e- enamel; and- cement.

are classified as mixed, as they secrete both mucous and serous secretions.

Gums. The mucous membrane is represented by two layers: a squamous stratified highly keratinized epithelium and a lamina propria. There are no glands, lymph nodes and submucosal layer. The mucous membrane fuses with the periosteum of the jawbone. In the region of the horny folds of the upper jaw, the horny layer of the epithelium reaches its greatest development in ruminants. The main plate is rich in elastic fibers and blood vessels.

Teeth referred to as derivatives of the oral mucosa. With their help, animals capture, hold and grind food.

Rice. 253. Dentin and dental pulp:

I - dentin; II- predentin; III - peripheral layer of pulp; IV- intermediate layer of pulp; V- the central layer of the pulp; 1 - dentinal tubules with processes of odontoblasts; 2 bodies of odontoblasts.

The tooth of adult animals is built from the crown, neck, root (Fig. 252). A crown is the portion of a tooth that protrudes above the gum. It is covered in enamel. The root of the tooth is immersed in the gum, lies in the hole of the bone jaw, lined with periosteum; firmly fixed with a circular ligament. The neck is located between the crown and the root. This is the part of the tooth that is covered only by the gum. In the central part of the crown there is a cavity of the tooth, which in the root of the tooth passes into the canal of the tooth. The number of canals in multi-rooted teeth corresponds to the number of roots.

The main structures of the tooth are: dentin, enamel, cement, pulp. The cavity of the tooth and the canal of the tooth root are filled with pulp in the form of fine fibrous connective tissue. In its surface layer there are several rows of cells of mesenchymal origin. They are called odontoblasts and have a pear shape, basophilic fine-grained cytoplasm, and a basally located nucleus. A long process extends from the outer surface of the odontoblast. It penetrates into the dentin located outside the pulp and lies there in the dentinal tubule (Fig. 253). Odontoblasts are similar in structure and value to osteoblasts of bone tissue. Between the odontoblasts are thin collagen fibers that pass into the collagen fibers of the dentin. Deeper than the layer of differentiated odontoblasts lies a layer of poorly differentiated cells, from which odontoblasts develop. The next layer of pulp consists of loose connective tissue rich in blood vessels and nerve fibers.

Dentin makes up the main part of the crown of the neck and root of the tooth. This is a type of bone tissue characterized by significant hardness. It contains the main substance and the thinnest radial processes of odontoblasts, the bodies of which form the surface layer of the dental pulp. The processes of odontoblasts lie in dentinal tubules, through which nutrients pass to the dentin.

In the dentin of the root, the dentin tubules branch; in the dentin of the crown, they do not form lateral branches.

The main substance of dentin consists of bundles

Rice. 254. Histological structure of teeth:

A - the structure of a horse's tooth on a transverse section (according to Ellenberger); one, 3 - cement; 2 - dentin; 4 - enamel; B - enamel prisms (according to Trautman and Fibiger).

collagen fibers and an adhesive containing a large percentage of lime, calcium salts are deposited.

The process of calcification of dentin proceeds unevenly. In the peripheral areas of the dentin, there are less calcified areas called interglobular spaces. They look like cavities with uneven surfaces. In the crown of the tooth, interglobular spaces are more extensive than in the root, where they are smaller but more numerous. Interglobular spaces play an important role in tooth nutrition.

The dentin of the root of the tooth is covered with cement from the outside. It is built from typical coarse fibrous tissue, so its strength is much lower than that of dentin and enamel. The cement is fed through the periosteum of the hole. Cement perforating fibers pass from the periosteum into the cementum, which carry out its connection.

Dentin in the area of ​​the crown of the tooth is covered with enamel. This is the strongest part of the tooth. The strength is due to the low content of organic matter (3 - 4%). Enamel is built from enamel prisms glued together with the same strong adhesive. All enamel prisms of the enamel layer have a radial orientation (Fig. 254). Calcification of the enamel proceeds unevenly, so it has lines that are parallel to the surface of the tooth. Outside, the enamel is covered with a thin cuticle, which is quickly erased on the chewing surface of the tooth.

The epithelium and mesenchyme of the main plate of the oral mucosa take part in the development of the tooth. After the formation of the bone base of the jaw of their stratified squamous epithelium, a continuous epithelial plate, called the dental plate, grows deep into the mesenchyme. On its outer surface, in an amount corresponding to future teeth, epithelial outgrowths in the form of caps are formed, called enamel organs (Fig. 255). Mesenchymal papillae grow into the enamel organs from the mesenchyme. Later, these beginnings

Rice. 255. Scheme of tooth development:

a- gingival epithelium; b - dental plate; in- epithelial dental organs; G- dental papillae (according to Ster).

overgrown with a compacted layer of mesenchyme and a mesenchymal sac is formed. The enamel organs elongate and, with their proximal ends, enter the sockets of the bone jaw. In the wall of the enamel organ, the outer, middle and inner layers can be distinguished. The outer layer consists of flat enamel cells, the middle layer is represented by several rows of stellate multi-processed cells of the pulp of the enamel organ, the inner one is a layer of cylindrical enamel cells located around the mesenchymal papilla. The latter produce tooth enamel and are called adamantoblasts. At the same time, the outer cells of the mesenchymal papilla become elongated with a thin long process extending from the distal part of the cell. These cells are called odontoblasts. They produce dentin.

Consequently, at the middle stage of tooth development, two rows of cells are formed, developing from different embryonic rudiments: epithelial cells of the enamel organ - adamantoblasts and cells of the mesenchymal papilla - odontoblasts (Fig. 256).

Then dentin develops. Odontoblasts in the zone of contact with adamantoblasts produce a layer of soft substance - predentin. The processes of odontoblasts grow into it, and the soft predentin turns into hard dentin. Odontoblasts move deep into the papilla, and their processes remain in the dentin. Located in the dentin tubules, they penetrate the entire dentin radially. Dentin is covered with enamel. It is formed by adamantoblasts: each cell deposits a column of soft matter. With the lengthening of these columns, the adamantoblasts become shorter and then completely disappear. The columns calcify and become prisms, the latter stick together and also calcify.

The cementum of the tooth is formed from the mesenchymal sac of the enamel organ, and the pulp of the tooth is formed from the mesenchymal papilla.

Language participates in the intake and chewing of food, determining its taste, swallowing, and in dogs it is also an organ of thermoregulation.

The tongue consists of a muscular base covered with a mucous membrane.

The muscular base is formed by striated muscle tissue, the fibers of which are located in three mutually perpendicular directions. In the muscular base and mucous membrane of the tongue there are salivary glands: by structure they are referred to as complex alveolar or tubular-alveolar, and by the nature of the secretion produced - to mucous, serous, mixed.

Rice. 256. Middle stage of tooth development:

1 - gingival epithelium; 2 - dental plate; 3 - enamel organ; 4 - dental papilla; 5 - dental pouch; 6 - bone of the lunula; 7 - odontoblasts; 8 - pulp of the enamel organ; 9 - adamantoblasts; 10 - outer cells of the enamel organ; 11 - dentin; 12 - enamel (according to Nemilov).

Rice. 257. Filiform papillae of the tongue:

1 2 3 - blood vessels; 4 5 - secondary papilla; 6 - striated muscle fibers.

The mucous membrane of the tongue is built of two layers: the epithelial layer and the main plate. The epithelial layer is represented by a squamous stratified epithelium, which forms a layer of keratinizing cells on the back of the tongue, which is absent on the lateral and lower surfaces. The mucous membrane of the back of the tongue forms four types of papillae: filiform, mushroom-shaped, roller-shaped, leaf-shaped, built of the same type; the base of each papilla is represented by an outgrowth of the main lamina of the mucous membrane - the connective tissue papilla, which is covered on the outside with a flat stratified keratinized or non-keratinized epithelium. The structure of the papillae is due to their functional significance.

Filiform papillae (Fig. 257) are the most common in animals. They are scattered over the entire dorsal surface of the tongue, perform a mechanical function and roughen the tongue. The connective tissue papilla has a filiform or conical shape. Secondary outgrowths may form on its surface. From above, the papilla is covered with stratified squamous keratinized epithelium.

The horny cap is formed from superficial keratinized cells. Filiform papillae of this type are very common in carnivorous animals.

Fungiform papillae (Fig. 258) are located between the filiform papillae on the dorsal surface of the tongue. They perceive temperature, taste irritations, perform a tactile function. The connective tissue papilla, similar in shape to the expanded part of the fungus, is covered with a squamous non-keratinized stratified epithelium. Taste buds lie on the lateral surfaces of the papilla in its epithelial layer.

The taste bud consists of elongated cells that are tightly adjacent to each other. Their longitudinal axis is oriented perpendicular to the surface of the tongue. The cells of this kidney are located on the basement membrane. It communicates with the oral cavity through the taste pore, which passes into the taste fossa. The taste bud is built from taste and supporting (supporting) cells (Fig. 259). Taste cells have oval nuclei located in the basal part of the cell. The cytoplasm contains intensely developed profiles of the smooth endoplasmic reticulum and many mitochondria. The membrane of the apical pole of the cell with its characteristic receptors forms microvilli that increase the perceiving surface. Between the microvilli is an electron-dense substance. It is characterized by high activity of phosphatase and protein content, mucoproteps, which play an important role in the process of taste reception.

Supporting cells are characterized by larger nuclei. In connection with their secretory function in the cytoplasm, the granular and agranular endoplasmic reticulum, the Golgi complex, as well as bundles of tenofilaments are well developed. Support cells are located between taste cells and nerve fibers. The latter penetrate into the taste bud from the connective tissue of the main plate and, passing between the cells, end with nerve endings on the lateral surface of the taste cells. Excitation in the form of a nerve impulse from the taste bud passes through the nerve endings along the nerve fibers to the central links of the taste analyzer.

The grooved (roll-shaped) papilla lies deep in the mucous membrane and does not protrude above the surface of the tongue (Fig. 260). It is surrounded by a roller, which is delimited from the papilla by a groove. The epithelium covering the papilla is not keratinized. Rows of taste buds lie in the epithelium of the lateral surfaces of the papilla. These papillae perform the function of an organ of taste, they are large in size, few in number, located at the root of the tongue.

Foliate papillae are not found in all animals (ruminants are absent). The shape is similar to a leaf.

Rice. 258. Fungiform papilla of the tongue of a cow:

1 - stratified squamous epithelium; 2 - the main plate of the mucous membrane; 3 - blood vessels; 4 - primary papilla of connective tissue; 5 - secondary papilla; 6 - the basis of the language; a - striated muscle fiber - longitudinal section and b - transverse section (according to Tinyakov).

Rice. 259. Structure of taste buds:

A - microscopic structure: 1 - stratified squamous epithelium of the papilla; 2 - taste time; 3 - supporting cells of the taste bud; 4 - receptor cells; 5 - pins; 6 - connective tissue. B- electron microscopic structure: 1 - taste receptor cell: 2 - supporting cell; 3 - basal cell; 4 - epithelial cell; 5 - microvilli; 6 - nerve endings; 7 - nerve fibers; 8 - mucoproteins (Fig. Pevzner). AT- diagram of the electron microscopic structure of receptor cells: 1 - taste time; 2 - villi; 3 - cytoplasm; 4 - synapse; 5 - nucleus.

Rice. 260. Rolled papilla of the tongue:

1 - stratified squamous epithelium; 2 - own record; 3 - secondary papillae; 4 - ditch; 5 - roller; 6 - smooth muscle cells; 7 - taste bud; 8 - terminal sections of the serous salivary glands; 9 - terminal sections of the mucous salivary glands; 10 - striated muscle fibers; 11 - output (duct of the salivary gland.

Located on the lateral surface of the root of the tongue, one on each side. They consist of long folds of mucous membrane oriented across the tongue. In addition, each mucosal fold on the cut is seen as a secondary papilla. Numerous taste buds are located in the epithelium of the lateral surfaces of the secondary papillae. Therefore, the foliate papilla also refers to the taste buds.

In the spaces between the secondary papillae, the excretory ducts of the salivary glands of the tongue may open.

We all have about 10,000 taste buds, which are located mainly on the surface of the tongue and in the soft tissues of the mouth. They are very sensitive and specially located in such a place that we are able to distinguish food by taste, preferring one food and rejecting another.

chemical sensation

Taste, like smell, is a chemical sensation. It works by a reaction between the chemical elements in food and the sensory elements found in special cells that form taste buds. The reaction is transmitted by nerve endings to the brain in the form of a taste sensation.

The tongue is thus the main organ of taste, since the food that the body takes in goes first into the mouth. The upper surface of the tongue is covered with numerous small growths, tubercles. Around them clusters of taste buds are formed. At the same time, some of them are in the larynx, on the soft palate and on the epiglottis.

taste buds

There are three types of taste papillae, papillae (the Latin word papillae literally means a protrusion in the form of a nipple). We list in order of increasing size: filiform (cone-shaped and filamentous), fungiform (mushroom-shaped) and gutter-shaped (cylindrical). In humans, the last two types are more present.

Fungiform palillae are located over the entire surface of the tongue, in greater numbers - on the sides and at the tip. There are 7 to 12 gutter papillae, the largest, at the back of the tongue. They are arranged in the form of a flat V. Taste buds cover the sides of the gutter papillae and the upper plane of the fungiform papillae.

Each receptor papilla consists of 40 to 100 epithelial cells. These cells are part of the epithelium - a layer that covers the entire surface and cavities of our body.

There are three types of cells in taste buds: supporting, receptor (sensitive) and basal (at the base). Receptor cells are also called gustatory cells because they provide a signal for taste sensations. The supporting cells make up the bulk of the papilla and separate the taste cells from one another. The cells of the receptor papilla are constantly updated - the usual life cycle is about 10 days.

Parts of the tongue

Epiglottis. A small number of taste buds are located here, extending all the way to the beginning of the digestive tract.

palatine tonsil. There are two tonsils in the mouth. There are few taste buds on the soft tissues that support the amygdala.

Gutter papillae. Round in shape, forming (at the back of the tongue) an inverted V.

fungiform papillae. Reminiscent of mushrooms, mainly found on the sides and tip of the tongue

Cone-shaped papillae. Cone-shaped, located mainly at a distance from the median line of the tongue.

Taste pathway

From each taste cell, very thin sensitive hairs sprout (through the epithelial cover). On the surface of the epithelium, they are washed by saliva, which is mixed with a food lump intended for a taste test. These hairs are sometimes referred to as sensory membranes, reflecting their initiatory role in the transmission of taste sensations.

Sensory nerve cells coil around taste cells. From here comes the impulse sent to the brain. The transmission of these signals from taste cells to brain cells is called the "gustatory pathway."

Taste Mechanism

As soon as the food mixed with saliva, the taste buds were signaled to act. Taste cells transform the chemical reaction of taste into a nerve impulse. When the impulse reaches the brain, the analysis of taste information will begin.

When the chemicals in the food react with the taste cells, a nerve impulse is sent to the thalamus, the subcortical center for all kinds of general sensibility. This brain structure processes a variety of impulses and combines similar ones. Then the thalamus sends them to the structure that is responsible for the sense of taste - the gustatory nerve of the cerebral cortex.

The thalamus itself is unable to fully appreciate the quality of taste. This is the work of the more sensitive taste nerve of the cerebral cortex.

Taste nerve of the cerebral cortex

This organ determines the quality of taste. The food substance must be mixed with saliva and come into contact with hairs called taste. From this moment, nerve impulses begin to be transmitted to the brain.

Impulses are sent along the branches of the facial nerves from the taste buds located on the first two thirds of the tongue.

The lingual branch of the glossopharyngeal nerves serves the posterior third of the tongue. It appears that the flow of taste information to the brain is two-way, in order to satisfy the body's need for certain foods.

Taste cells in different parts of the tongue have a different threshold of sensitivity, which activates the beginning of recognition. The bitter part of the tongue can detect poisons in the smallest concentrations. This explains why the seeming inconvenience of being on the "back" of the tongue works as a precautionary measure before swallowing food. Acid receptors are less sensitive. The sensitivity of sweet and salty receptors is even less. The speed of the reaction of receptors to a new taste sensation is from 3 to 5 minutes.

What is often called taste is actually its combination with the sensation of smell. Taste is 80 percent smell, which is why cold, unflavoured food is not appetizing.

There are also other receptors on the tongue that help heighten the sense of taste. Spicy foods increase the pleasure of eating because they activate pain receptors on the tongue.

The structure of the taste bud

Taste hairs- sensitive microvilli of taste cells, washed by saliva.

taste cell- also called receptor cell.

Support cells- isolate taste cells from each other, as well as from cells of the lingual epithelium.

epithelial cells- the outer covering of the tongue.

Nerve endings- transmit their pulses to the part of the brain - the thalamus.

Longitudinal section of the taste bud

Papillae of the tongue, which do not recognize the taste, but crush food due to their abrasive surface.

taste bud- in group clusters on the basis of the papilla.

excretory ducts- Salivary glands of Ebner.

Abner glands- release secretion to wash the taste bud.

Tongue sensitivity to the four tastes

Taste sensations can be grouped into 4 main categories. It is sweet, sour, salty and bitter. Different parts of the tongue have different sensitivity to each of the tastes, although there is no clear structural separation between the taste buds.

The tip of the tongue is most sensitive to sweet and salty foods. The sides of the tongue recognize the sour taste. The back of the tongue reacts most strongly to bitter. However, this separation is not absolute, as most of the taste buds respond to two, three, and sometimes all four taste sensations.

Certain food substances tend to change flavor as they move through the mouth. Saccharin, for example, tastes sweet at first and then turns bitter. Some natural poisons and spoiled food taste bitter. This is most likely why bitterness receptors are located at the back of the tongue as a protective barrier before swallowing. The “back” of the tongue serves as a guard in the mouth, rejecting the intake of “bad” food.

The human body. Outside and inside. №8 2008

thinner and more transparent. There is no hair in this area, the sweat glands gradually disappear, and only the sebaceous glands remain, opening their ducts to the surface of the epithelium. There are more sebaceous glands in the upper lip, especially in the corner of the mouth. The lamina propria is a continuation of the connective tissue part of the skin; her papillae in this zone are low. The inner zone of the intermediate section of the lip (the so-called red border) in newborns is covered with epithelial papillae, which are sometimes called villi. These epithelial papillae gradually smooth out and become inconspicuous as the organism grows. The epithelium of the inner zone of the transitional part of the lip of an adult is 3-4 times thicker than in the outer zone, it is devoid of the stratum corneum. The sebaceous glands are usually absent here. Loose fibrous connective tissue lying under the epithelium, protruding into the epithelium, forms very high papillae, in which there are numerous capillaries. The blood circulating in them shines through the epithelium and causes the red color of the lips. The papillae contain a huge number of nerve endings, so the red edge of the lip is very sensitive.

Mucous lip lined with stratified squamous nonkeratinized epithelium

characteristic of the oral cavity. However, in the cells of the surface layer of the epithelium, a small amount of keratin grains can still be found. The epithelial layer in the mucous section of the lip is much thicker than in the skin. The lamina propria here forms papillae (less high than in the transition section). The muscular lamina of the mucous membrane is absent, and therefore the lamina propria without a sharp border passes into the submucosa, adjacent directly

to striated muscles.

AT submucosal layer contains secretory compartmentssalivary labial glands(gll. labiales). The glands are quite large, sometimes reaching the size of a pea. By structure, these are complex alveolar-tubular glands (see the classification of glands). By the nature of the secret, they belong to the mixed mucous-protein glands. Their excretory ducts are lined with stratified squamous non-keratinized epithelium and open on the surface of the lip.

AT the submucosal base of the mucous membrane of the lip contains arteries and an extensive venous plexus, which also extends into the red part of the lip.

Human language, in addition to participation in taste perception, mechanical processing of food and the act of swallowing , is the organ of speech. The basis of the tongue is striated muscle tissue of the somatic type.

The tongue is covered with a mucous membrane. Its relief is different on the lower, lateral and upper surfaces of the tongue. The simplest structure has mucous membrane on its lower surface. The epithelium here is stratified squamous, non-keratinizing.

Zolina Anna, TGMA, medical faculty.

The lamina propria protrudes into the epithelium, forming short papillae. The lamina propria is followed by the submucosa, which is adjacent directly to the muscles. Due to the presence of a submucosa, the mucous membrane of the lower surface of the tongue is easily displaced.

The mucous membrane of the upper and lateral surfaces of the tongue motionless fused with his muscular body and equipped with special formations - papillae. The submucosa is absent. In human language there is4 types of papillae of the tongue:

 filiform (papillae filiformes),

 mushroom-shaped (papillae fungiformes),

 grooved (papillae vallatae) and

 leaf-shaped (papillae foliatae).

All papillae of the tongue are derivatives of the mucous membrane and are built according to a general plan. The surface of the papillae is formed by a stratified squamous non-keratinized or partially keratinized (in filiform papillae) epithelium lying on the basement membrane. The basis of each papilla is an outgrowth (primary papilla) of its own connective tissue layer of the mucous membrane. From the apex of this primary papilla several (5–20) thinner connective tissue secondary papillae protrude into the epithelium. In the connective tissue basis of the papillae of the tongue there are numerous blood capillaries that are translucent through the epithelium (except for the filiform ones) and give the papillae a characteristic red color.

Filiform papillae the most numerous, evenly cover the upper surface of the tongue, concentrating especially in the angle formed by the papillae, surrounded by a shaft. In size, they are the smallest among the papillae of the tongue. Their length is about 0.3 mm. Along with filiform papillae, there are conical papillae (papillae conicae). In a number of diseases, the process of rejection of superficial keratinizing epithelial cells can slow down, and epithelial cells, accumulating in large quantities on the tops of the papillae, form powerful horny layers. These masses, covering the surface of the papillae with a whitish film, create a picture of the coating of the tongue with a coating.

fungiform papillae few and located on the back of the tongue among the filiform papillae. Their greatest number is concentrated at the tip of the tongue and along its edges. They are larger than filiform - 0.7-1.8 mm in length and about 0.4-1 mm in diameter. The bulk of these papillae are mushroom-shaped with a narrow base and a wide apex. Among them there are conical and lenticular forms.

In the thickness of the epithelium are taste buds (gemmae gustatoriae), located most often in the area of ​​\u200b\u200bthe "cap" of the mushroom papilla. In sections through this zone, up to 3-4 taste buds are found in each mushroom papilla. Some papillae lack taste buds.

Zolina Anna, TGMA, medical faculty.

Grooved papillae (or papillae surrounded by a shaft) found on the upper surface of the root of the tongue in an amount of 6 to 12. They are located between the body and the root of the tongue along the boundary line. They are clearly visible even to the naked eye. Their length is about 1-1,5 mm, diameter 1-3 mm. In contrast to the filiform and fungiform papillae, which clearly rise above the level of the mucous membrane, the upper surface of these papillae lies almost on the same level with it. They have a narrow base and a wide, flattened free part. Around the papilla there is a narrow, deep gap - a groove (hence the name - grooved papilla). The gutter separates the papilla from the ridge - a thickening of the mucous membrane surrounding the papilla. The presence of this detail in the structure of the papilla was the reason for the emergence of another name - "a papilla surrounded by a shaft." Numerous taste buds are located in the thickness of the epithelium of the lateral surfaces of this papilla and the ridge surrounding it. In the connective tissue of the papillae and ridges, there are often bundles of smooth muscle cells arranged longitudinally, obliquely, or circularly. The reduction of these bundles ensures the convergence of the papilla with the roller. This contributes to the most complete contact of nutrients entering the gutter with taste buds embedded in the epithelium of the papilla and ridge. In the loose fibrous connective tissue of the base of the papilla and between the bundles of striated fibers adjacent to it, there are the terminal sections of the salivary protein glands, the excretory ducts of which open into the gutter. The secret of these glands washes the trough of the papilla and cleanses it of food particles accumulating in it, exfoliating epithelium and microbes.

Foliate papillae Languages ​​are well developed only in children. They are represented by two groups located on the right and left edges of the tongue. Each group includes 4-8 parallel papillae separated by narrow spaces. The length of one papilla is about 2-5 mm. Taste buds are enclosed in the epithelium of the lateral surfaces of the papilla. The excretory ducts of the salivary protein glands open into the spaces separating the foliate papillae. Their terminal sections are located between the muscles of the tongue. The secret of these glands washes the narrow spaces between the papillae. In an adult, the foliate papillae are reduced, and in places where the protein glands were previously located, adipose and lymphoid tissues develop.

Root mucosa tongue is characterized by the absence of papillae. However, the surface of the epithelium here is not even, but has a number of elevations and depressions. Elevations are formed due to the accumulation of lymph nodes in the lamina propria of the mucous membrane, sometimes reaching 0.5 cm in diameter. Here, the mucous membrane forms depressions - crypts, into which the ducts of numerous salivary mucous glands open. The collection of accumulations of lymphoid tissue in the root of the tongue is called the lingual tonsil.

Zolina Anna, TGMA, medical faculty.

The muscles of the tongue form the body of this organ. The bundles of striated muscles of the tongue are located in three mutually perpendicular directions: some of them lie vertically, others longitudinally, and others transversely. The muscles of the tongue are divided into right and left halves by a dense connective tissue septum. Loose fibrous connective tissue lying between individual muscle fibers and bundles contains many fatty lobules. The end sections of the salivary glands of the tongue are also located here. On the border between the muscular body and the lamina propria of the mucous membrane of the upper surface of the tongue, there is a powerful connective tissue lamina, consisting of bundles of collagen and elastic fibers intertwining like a lattice. It forms the so-called mesh layer. This is a kind of aponeurosis of the tongue, which is especially strongly developed in the region of the grooved papillae. At the end and at the edges of the tongue, its thickness decreases. Cross-striped muscle fibers, passing through the holes of the mesh layer, are attached to small tendons formed by bundles of collagen fibers lying in the lamina propria.

Salivary glands of the tongue(gll. lingualis) are divided into three types: protein, mucous and mixed.

Protein salivary glands located near the grooved and foliate papillae in the thickness of the tongue. They are simple tubular branched glands. Their excretory ducts open into grooves of papillae surrounded by a shaft, or between foliate papillae, and are lined with stratified squamous epithelium, sometimes containing cilia. The end sections are represented by branched tubules with a narrow lumen. They consist of conical cells that secrete a protein secret, between which intercellular secretory capillaries pass.

Mucous glands located mainly at the root of the tongue and along its lateral edges. These are solitary simple alveolar-tubular branched glands. Their ducts are lined with stratified epithelium, sometimes provided with cilia. At the root of the tongue, they open into the crypts of the lingual tonsil. The tubular terminal sections of these glands consist of mucous cells.

mixed glands located in its anterior region. Their ducts (about 6 million) open along the folds of the mucous membrane under the tongue. Secretory departments of mixed glands are located in the thickness of the tongue.

Blood supply of the tongue carried out by the lingual arteries entering it, which branch out abundantly and form a wide network in the muscles of the tongue. They also give branches to the superficial parts of the tongue. In the reticular layer of the tongue, the vessels are located horizontally, and then vertical terminal branches depart from them to the papillae of the mucous membrane. The terminal branches form a capillary network in the connective tissue papillae, from which one loop of blood capillaries enters each smaller papilla. Blood from the surface layers of the tongue flows into the venous plexus, located in its own layer of the mucous membrane. Larger

Zolina Anna, TGMA, medical faculty.

the venous plexus is located at the base of the tongue. Small lymphatic vessels also form a network in the lamina propria. This network is connected to a larger network present in the submucosa of the lower surface of the tongue.

Lymphatic vessels are also found in large numbers in the region of the tonsil of the tongue.

Innervation. The ramifications of the hypoglossal nerve and the tympanic string form numerous motor nerve endings on striated muscle fibers. Sensitive innervation of the anterior 2/3 of the tongue is carried out by the branches of the trigeminal nerve, the posterior 1/3 by the branches of the glossopharyngeal nerve. In the own plate of the mucous membrane of the tongue there is a well-defined nerve plexus, from which the nerve fibers depart to the taste buds, epithelium, glands and blood vessels. The nerve fibers entering the epithelium branch out among the epithelial cells and end with free nerve endings.

Lymphoepithelial pharyngeal ring of Pirogov-Waldeyer. Tonsils.

On the border of the oral cavity and pharynx in the mucous membrane there are large accumulations of lymphoid tissue. Collectively, they form a lymphoepithelial pharyngeal ring surrounding the entrance to the respiratory and digestive tracts. The largest accumulations of this ring are called tonsils. According to their location, they are distinguished palatine tonsils, pharyngeal tonsils, lingual tonsils. In addition to the tonsils listed above, in the mucous membrane of the anterior part of the digestive tube there are a number of accumulations of lymphoid tissue, of which the largest are accumulations in the area of ​​the auditory tubes - tubal tonsils and in the ventricle of the larynx - laryngeal tonsils.

Tonsils perform an important protective function in the body, neutralizing microbes that constantly enter the body from the external environment through the nasal and oral openings. Along with other organs containing lymphoid tissue, they provide the formation of lymphocytes involved in the reactions of humoral and cellular immunity.

Development. palatine tonsils are laid at the 9th week of embryogenesis in the form of a deepening of the pseudostratified ciliated epithelium of the lateral wall of the pharynx, under which lie compactly located mesenchymal cells and numerous blood vessels. At the 11-12th week, the tonsillar sinus is formed, the epithelium of which is rebuilt into a multilayer flat, and the reticular tissue differentiates from the mesenchyme; vessels appear, including postcapillary venules with high endotheliocytes. The organ is colonized by lymphocytes. At the 14th week, among the lymphocytes, mainly T-lymphocytes (21%) and a few B-lymphocytes (1%) are determined. At the 17-18th week, the first lymph nodes appear. K 19-

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Pharyngeal tonsil develops on the 4th month of the intrauterine period from the epithelium and underlying mesenchyme of the dorsal pharyngeal wall. In the embryo, it is covered with multi-row ciliated epithelium. Lingual tonsil laid on the 5th month.

The tonsils reach their maximum development in childhood. The beginning of the involution of the tonsils coincides with the period of puberty.

Structure. palatine tonsils in an adult organism, they are represented by two oval-shaped bodies located on both sides of the pharynx between the palatine arches. Each tonsil consists of several folds of the mucous membrane, in the own plate of which there are numerous lymphatic nodules (noduli lymphathici). 10-20 crypts (criptae tonsillares) extend from the surface of the tonsil deep into the organ, which branch out and form secondary crypts. mucous membrane covered with stratified squamous nonkeratinized epithelium. In many places, especially in crypts, the epithelium is often infiltrated (populated) with lymphocytes and granulocytes. Leukocytes penetrating into the thickness of the epithelium usually come to its surface in greater or lesser numbers and migrate towards bacteria that enter the oral cavity along with food and air. Microbes in the amygdala are actively phagocytized by leukocytes and macrophages, while some of the leukocytes die. Under the influence of microbes and various enzymes secreted by leukocytes, the tonsil epithelium is often destroyed. However, after some time, due to the multiplication of cells of the epithelial layer, these areas are restored.

own record mucous membrane forms small papillae protruding into the epithelium. Numerous lymph nodules are located in the loose fibrous connective tissue of this layer. In the centers of some nodules, lighter areas are well expressed - germinal centers. Lymphoid nodules of the tonsils are most often separated from each other by thin layers of connective tissue. However, some nodules may coalesce. The muscular plate of the mucous membrane is not expressed.

Submucosa, located under the accumulation of lymphoid nodules, forms a capsule around the tonsil, from which connective tissue septa extend into the depth of the tonsil. In this layer, the main blood and lymphatic vessels of the tonsil and the branches of the glossopharyngeal nerve, which innervate it, are concentrated. The secretory sections of small salivary glands are also located here. The ducts of these glands open on the surface of the mucous membrane located around the tonsil. Outside of the submucosa lie the striated muscles of the pharynx - an analogue of the muscular membrane.

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Pharyngeal tonsil located in the area of ​​the dorsal wall of the pharynx, lying between the openings of the auditory tubes. Its structure is similar to other tonsils. In an adult organism, it is lined with stratified squamous non-keratinized epithelium. However, in the crypts of the pharyngeal tonsil and in the adult, there are sometimes areas of pseudostratified ciliated epithelium, which is characteristic of the embryonic period of development.

In some pathological conditions, the pharyngeal tonsil can be greatly enlarged (the so-called adenoids).

Lingual tonsil located in the mucous membrane of the root of the tongue. The epithelium covering the surface of the tonsil and lining the crypts is stratified squamous, non-keratinized. The epithelium and the underlying lamina propria are infiltrated with lymphocytes penetrating here from the lymph nodes. At the bottom of many crypts, the excretory ducts of the salivary glands of the tongue open. Their secret contributes to the washing and cleansing of the crypts.

Salivary glands

General morphofunctional characteristics. The excretory ducts of three pairs of large salivary glands open into the oral cavity:parotid, submandibular and sublingual . In addition, in the thickness of the oral mucosa there are numerous small salivary glands:labial, buccal, lingual, palatal.

Epithelial structures of all salivary glands develop from ectoderm, as well as the stratified squamous epithelium lining the oral cavity. Therefore, the structure of their excretory ducts and secretory sections is characterized by multilayeredness.

The salivary glands are complex alveolar or alveolar tubular glands. They consist of end sections and ducts that remove the secret.

The end sections (portio terminalis) are of three types according to the structure and nature of the secretion secreted: protein (serous), mucous and mixed (i.e., protein-mucous).

excretory ducts salivary glands are divided into intralobular(ductus interlobularis), including insertion (ductus intercalates) and striated (ductus striatus), interlobular (ductus interlobularis) excretory ducts and ducts of the gland

(ductus excretorius seu glandulae).

Protein glands secrete a liquid secret rich in enzymes. The mucous glands form a thicker, viscous secretion with a high content of mucin, a substance that contains glycoproteins. According to the mechanism of secretion from cells, all salivary glands are merocrine.

The salivary glands perform exocrine and endocrine functions. exocrine function consists in the regular separation of saliva into the oral cavity. In its composition

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includes water (about 99%), protein substances, including enzymes, inorganic substances, as well as cellular elements (epithelial cells and leukocytes).

Saliva moisturizes food, giving it a semi-liquid consistency, which facilitates chewing and swallowing. Constant wetting of the mucous membrane of the cheeks and lips with saliva contributes to act of articulation. One of the important functions of saliva is enzymatic food processing. Saliva enzymes can participate in the breakdown of: polysaccharides (amylase, maltase, hyaluronidase), nucleic acids and nucleoproteins (nucleases and kallikrein), proteins (kallikrein-like proteases, pepsinogen, trypsin-like enzymes), cell membranes (lysozyme).

In addition to their secretory function, the salivary glands perform excretory function. With saliva, various organic and inorganic substances are released into the external environment: uric acid, creatine, iron, iodine, etc. The protective function of the salivary glands consists in the release of a bactericidal substance - lysozyme, as well as class A immunoglobulins.

endocrine function salivary glands is provided by the presence in saliva of biologically active substances such as hormones - insulin, parotin, nerve growth factor (NGF), epithelial growth factor (EGF), thymocyte-transforming factor (TTF), lethality factor, etc. The salivary glands are actively involved in the regulation of water-salt homeostasis.

Development. Bookmark parotid glands occurs at the 8th week of embryogenesis, when epithelial strands begin to grow from the epithelium of the oral cavity into the underlying mesenchyme towards the right and left ear openings. From these strands, numerous outgrowths bud, forming first the excretory ducts, and then the terminal sections. At the 10-12th week there is a system of branched epithelial cords, ingrowth of nerve fibers. At the 4-6th month of development, the terminal sections of the glands are formed, and by the 8-9th month gaps appear in them. Intercalary ducts and terminal sections in fetuses and children under two years of age are represented by typical mucous cells. From the mesenchyme, by 5-5½ months of embryogenesis, the connective tissue capsule and layers of interlobular connective tissue differentiate. At first, the secret has a mucous character. In the last months of development, fetal saliva exhibits amylolytic activity.

submandibular glands are laid at the 6th week of embryogenesis. At the 8th week, gaps form in the epithelial strands. The epithelium of the primary excretory ducts is first two-layered, then multilayered. Terminal sections are formed on the 16th week. The mucous cells of the terminal sections are formed in the process of mucus formation of the cells of the intercalary ducts. The process of differentiation of the terminal sections and intralobular ducts into intercalary sections and salivary tubes continues in the postnatal period of development. In newborns, in the terminal sections, elements are formed, consisting of glandular cells of a cubic and prismatic shape, forming

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protein secretion (Crescent Gianuzzi). Secretion in the terminal sections begins in 4-month-old fetuses. The composition of the secret is different from the secret of an adult. The sublingual glands are laid on the 8th week of embryogenesis in the form of processes from the oral ends of the submandibular glands. On the 12th week, budding and branching of the epithelial primordium are noted.

parotid glands

The parotid gland (gl. parotis) is a complex alveolar branched gland that secretes a protein secret into the oral cavity, and also has an endocrine function. Outside, it is covered with a dense connective tissue capsule. The gland has a pronounced lobed structure. Interlobular ducts and blood vessels are located in the layers of connective tissue between the lobules.

The terminal sections of the parotid gland are proteinaceous (serous).They consist of cone-shaped secretory cells - protein cells, or serocytes (serocyti), and myoepithelial cells. Serocytes have a narrow apical part protruding into the lumen of the terminal section. It contains acidophilic secretory granules, the number of which varies depending on the phase of secretion. The basal part of the cell is wider and contains the nucleus. In the phase of secretion accumulation, cell sizes increase significantly, and after secretion they decrease, the nucleus becomes rounded. The secretion of the parotid glands is dominated by the protein component, but mucopolysaccharides are also often contained, so such glands can be called seromucous. Enzymes found in secretory granulesα-amylase, DNase. Cytochemically andelectron microscopicallythere are several types of granules - CHIC positive withelectron dense rim, CHIC-negativeand small homogeneous spherical shapes. Between the serocytes in the terminal sections of the parotid gland there are intercellular secretory tubules, the lumen of which has a diameter of about 1 micron. A secret is secreted from the cells into these tubules, which then enters the lumen of the terminal secretory section. The total secretory area of ​​the terminal sections of both glands reaches almost 1.5 m2.

Myoepithelial cells (myoepitheliocytes)make up the second layer of cells in the terminal secretory sections. By origin, these are epithelial cells, by function they are contractile elements resembling muscle cells. They are also called stellate epithelial cells, since they have a stellate shape and with their processes cover the terminal secretory sections like baskets. Myoepithelial cells are always located between the basement membrane and the base of the epithelial cells. With their contractions, they contribute to the secretion of the end sections.

The system of excretory ducts includes intercalated, striated, as well as interlobular ducts and the duct of the gland.

Intralobular intercalary ducts of the parotid glandstart directly from its terminal sections. They are usually highly branched. Insertion

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the ducts are lined with cuboidal or squamous epithelium. The second layer in them is formed by myoepitheliocytes. In cells adjacent to the acinus, electron-dense granules containing mucopolysaccharides are found; tonofilaments, ribosomes, and an agranular endoplasmic reticulum are also located here.

Striated salivary ducts are a continuation of the intercalary and are also located inside the lobules. Their diameter is much larger than the intercalary ducts, the lumen is well defined. The striated ducts branch and often form ampullar extensions. They are lined with a single layer of prismatic epithelium. The cytoplasm of cells is acidophilic. In the apical part of the cells, microvilli, secretory granules with contents of various electron densities, and the Golgi apparatus are visible. In the basal parts of the epithelial cells, the basal striation is clearly revealed, formed by mitochondria located in the cytoplasm between the folds of the cytolemma perpendicular to the basement membrane. In the striated sections, cyclic changes unrelated to the rhythm of the digestive process were revealed.

Interlobular excretory ducts lined with bilayer epithelium. As the ducts enlarge, their epithelium gradually becomes multilayered. The excretory ducts are surrounded by layers of loose fibrous connective tissue.

Parotid duct, starting in her body, passes through the masticatory muscle, and its mouth is located on the surface of the mucous membrane of the cheek at the level of the second upper molar (large molar). The duct is lined with stratified cuboidal, and at the mouth - with stratified squamous epithelium.

submandibular glands

Submandibular gland (gll. submaxillare) - complex alveolar(in places alveolar-tubular) branched gland. By the nature of the separated secret, it is mixed, protein-mucous. From the surface of the gland is surrounded by a connective tissue capsule.

Terminal secretory divisions submandibular gland of two types: protein and protein-mucous, but predominate in it protein terminals. Secretory granules of serocytes have a low electron density. Often inside the granules contains an electron-dense core. The terminal sections (acini) consist of 10-18 seromucous cells, of which only 4-6 cells are located around the lumen of the acinus. Secretory granules contain glycolipids and glycoproteins. Mixed end sections larger than protein, and consist of two types of cells - mucous and protein. Mucous cells(mucocyti) are larger than protein ones and occupy the central part of the terminal section. The nuclei of mucous cells are always located at their base, they are strongly flattened and compacted. The cytoplasm of these cells has a cellular structure due to the presence of a mucous secretion in it. A small number of protein cells covers the mucous cells in the form serous crescent(semilunum serosum). The proteinaceous (serous) crescents of Gianuzzi are characteristic structures of mixed glands. Between

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The tongue develops from 1-3 gill arches as a result of the fusion of 5 primordia. Gill arches - part (element) of the gill apparatus of the embryo. The tongue is a muscular organ, the basis is striated muscle tissue. Muscle fibers are located in 3 mutually perpendicular directions. Between the muscle fibers are layers of loose fibrous sdt with blood vessels, as well as the terminal sections of the lingual salivary glands. These glands, by the nature of the secret in the anterior part of the tongue, are mixed (mucous-protein), in the middle part of the tongue - protein, in the region of the root of the tongue - purely mucous.

The muscular body of the tongue is covered with a mucous membrane. On the lower surface, due to the presence of a submucosal base, the mucous membrane is mobile; there is no submucosa on the back of the tongue, so the mucous membrane is motionless in relation to the muscular body.

On the back of the tongue, the mucous membrane forms papillae: filiform, mushroom-shaped, foliate and grooved papillae are distinguished. The histological structure of the papillae is similar: the basis is an outgrowth from a loose mucosal lamina propria (having the form: filiform, mushroom-shaped, leaflet and anvil), outside the papillae are covered with stratified squamous non-keratinizing epithelium. An exception is the filiform papillae - in the region of the tops of these papillae, the epithelium has signs of keratinization or becomes keratinized. The function of the filiform papillae is mechanical, i.e. they work like scrapers. In the thickness of the epithelium of the fungiform, foliate and grooved papillae there are taste buds (or taste buds), which are receptors of the organ of taste. The taste bud has an oval shape and consists of the following types of cells:

1. Taste sensory epitheliocytes - spindle-shaped elongated cells; in the cytoplasm have agranular EPS. Mitochondria have microvilli on the apical surface. Between the microvilli is an electron-dense substance with a high content of specific receptor proteins - sweet-sensitive, acid-sensitive, salt-sensitive and bitter-sensitive. Sensory nerve fibers approach the lateral surface of the sensory epithelial cells and form receptor nerve endings.

2. Support cells - curved spindle-shaped cells that surround and support gustatory sensory epithelial cells.

3. Basal epitheliocytes - poorly differentiated cells, for regeneration of 1 and 2 cells.

The apical surfaces of taste bud cells form taste pits that open into the taste pore. Substances dissolved in saliva enter the taste pits, are adsorbed by the electron-dense substance between the microvilli of sensoepithelial cells, and act on the receptor proteins of the cell membrane, which leads to a change in the electric potential difference between the inner and outer surfaces of the cytolemma, i.e. the cell goes into a state of excitation and this is captured by the nerve endings.

SARATOV STATE

MEDICAL UNIVERSITY

DEPARTMENT OF HISTOLOGY, CYTOLOGY AND EMBRYOLOGY

ANNOTATION

EXAM SUBSTANCES

ON HISTOLOGY, CYTOLOGY AND

EMBRYOLOGY

FOR STUDENTS OF MEDICAL, PEDIATRIC AND DENTAL FACULTIES

EDUCATIONAL AND METHODOLOGICAL AID

SARATOV 2009

This study guide “Annotation of Exam Preparations in Histology, Cytology and Embryology” is intended to help students prepare for the state exam. This manual will also be useful for preparing the main thematic sections on histology (tests), for obtaining diagnostic skills and describing micropreparations.

Drug No. 1

Somites, chord.

Stain: hematoxylin.

The drug is a cross section of a chicken embryo at the stage of differentiation mesoderm and education axial organ rudiments. Find the upper germ layer at low magnification of the microscope - ectoderm, in which signs of a multilayer structure are found; visible under the ectoderm nervous a tube with clearance central channel, and under it is a dense strand of cells (on a cross section - rounded) - chord. Symmetrically from these rudiments of axial organs are located somites- areas of the dorsal mesoderm, in each of the somites three cell zones are distinguished: facing the ectoderm - dermatome, central - myotome, and the underlying sclerotome. On the periphery of the histological preparation - mesoderm lateral plates, split into two sheets: parietal(accompanies ectoderm) and visceral(accompanies the endoderm), which close coelomic cavity. Between the somite and the sheets of the splanchnotome is located segmental leg- intermediate mesoderm. On the opposite side of the ectoderm, a thin strip of flat cells is visible - endoderm. Primary blood vessels with nuclear formed elements in their lumen are visible on the sides of the notochord, near the somites and endoderm.

Drug No. 2

Elastic cartilage

Colour: orcein; the increase is small.

The drug is a section of the elastic cartilaginous tissue of the auricle. At low magnification, note the general plan of the structure of cartilage tissue. connective tissue perichondrium contains vessels and nerves for cartilage trophism, and consists, respectively, of two layers: outer - fibrous and internal - cellular containing cells - chondroblasts. Under the perichondrium is a thin layer single chondrocytes cartilage tissue; due to lack of maturity intercellular substance this zone is colored lighter than the deeper areas. Under the layer of single chondrocytes there is a zone mature cartilage, containing isogenic groups cartilage cells in the form of predominantly columns or chains; the elastic fibers of the ground substance are stained dark cherry or brown.

It should be noted that along the periphery of the cut, layers of the epidermis of the auricle (thin skin) with the corresponding derivatives are often visible: sebaceous and sweat glands and hair roots located in the dermis, passing into the perichondrium.

Drug No. 3

Cross section of the diaphysis of a tubular bone.

Color: thionine-picric acid; the increase is small.

The preparation is a transverse section of lamellar decalcified bone tissue in the area diaphysis. The outer layer of the cut is presented periosteum- periosteum, which is a dense unformed connective tissue. The periosteum has two layers: outer fibrous and inner with cells osteoblasts and contains vessels and nerves that provide trophic bone tissue. The periosteum is in most cases partially destroyed. Under the periosteum is a layer outdoor general plates; process cells are “embedded” between them - osteocytes dark brown. Behind the outer general is a layer osteons. Osteon is a layer of bone plates concentrically on top of each other with osteocytes between them and channel in the center. In addition to osteons, this layer contains intercalary records, which are the remains of the austen of previous generations and the result of bone tissue restructuring under the influence of osteoclasts- cells - resorbents of bone tissue. From the inside, the bone canal surrounds the layer internal general plates, this layer is similar in structure to the layer of outer general plates. From the internal general plates depart bone crossbeams inside the canal, between them in the bone is yellow bone marrow. From the inside, the surface of the inner general plates is coated endosteum- thin fibrous sheath.

Drug No. 4

Striated muscle tissue of the tongue.

Stain: iron hematoxylin; increase - small, large.

The drug is a section of the striated muscle tissue of the tongue. Muscle fibers in the tongue go in three mutually perpendicular directions, so to study them, you should pay attention to the longitudinal and transverse sections and study them at high magnification.

Cross sections of muscle fibers have a rounded or oval shape. Sarcolemma fibers form a contour line. The muscle nuclei are round in shape and their peripheral location is clearly visible. Cross sections of myofibrils have the appearance of dust-like granularity in the sarcoplasm. Around each fiber, soft-fibrous layers are visible. endomysium. Groups of muscle fibers are surrounded perimyzium, which is a wider layer of connective tissue, where cuts of blood vessels and nerves meet. On a longitudinal section of a muscle fiber, pay attention to striation(alternation of dark and light stripes, which is explained by the presence and heterogeneity of the structures of myofibrils). One can see the peripherally lying oval-shaped nuclei belonging to myosymplast or myosatellitocytes. Between individual muscle fibers, thin layers of loose connective tissue are visible with single connective tissue cells lying in them (they have dark elongated nuclei) that form endomysium.

At low magnification, with a general view of the preparation along the periphery of the cut, there is a squamous stratified epithelium, the layer of which is distinguished by a darker color. Under the epithelium is a layer of loose connective tissue, directly passing into the intermuscular connective tissue. The intermuscular loose connective tissue contains the vessels and nerves of the tongue: the shaped elements in the lumen of the vessels are painted in a dark, almost black color; sections of the nerve trunks have a lighter gray color and a fibrous structure; often you can find accumulations of adipocytes.