The structure, layers and types of the oral mucosa

The digestive system begins in the mouth. Mechanical processing of incoming food is carried out here.

The mucous membrane envelops the surface of the mouth, designed to protect it from any irritants.

The structure and construction of the oral mucosa are very complex and have their own characteristic features that distinguish it from other organs of the human body.

All of these unique features allow the shell to perform a wide variety of functions.

Mucosal histology

The oral cavity is enveloped in a membrane. It covers the inside of the cheeks, lips, alveolar processes, palate, tongue and bottom. She gets hydrated all the time through work salivary glands and has characteristic properties in its structure and implements functional tasks.

The most important functional activities:

1. Protection. It protects the coating from mechanical stress, from harmful bacteria and microbes that enter with food.
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2. Improving digestion. Salivary glands produce saliva, which helps digest food.
3. Feel. It helps to recognize taste, temperature, swallow food and respond to external stimuli.
4. Regulate heat. Mouth breathing can help warm your hands or regulate your body temperature.
5. Maintaining immunity. The mouth contains cells that affect the overall immunity of the body.
6. Suction. Some trace elements and drugs can be absorbed through the oral cavity.

The covering of the mouth can perform all these functions due to its unique structure. The surface design is rather heterogeneous and complex. In some parts it can move and pliable, in the rest it is motionless.

The following layers of the oral mucosa are distinguished:

• epithelial layer;
• directly the mucous layer;
• submucosal layer.

The entire membrane is enveloped in a flat epithelial layer that has many layers. In different parts of the cavity, it has a different structure. In areas of soft sky, lips, cheeks and bottom, it consists of a basal layer and a layer with spines and is not able to keratinize. Areas of the hard palate and gums are covered with granular and stratum corneum. have the ability to keratinize.

The process of hardening and exfoliation of particles occurs due to the fact that mechanical action is carried out on certain areas. This is the result of a response to irritation. Almost half of the entire area of ​​the mouth is subject to keratinization.

The size of the thickness of the epithelium varies in different areas. Places where the impact of external stimuli is minimal - the bottom of the mouth, the lower part of the tongue and lips - the cover is very thin. In other areas, it is much thicker. With increasing age of a person, the thickness of the layer changes. In childhood, it is very thin, then gradually thickens and becomes thin again by old age.

After the epithelial layer is mucous. It is based on connective tissue. With the help of a papilla-shaped eminence, it passes into the epithelial layer. Each papilla is equipped with many nerve fibers and blood vessels. Due to this connection of the two layers between them, the exchange of nutrients and their strong union takes place.

The mucous layer contains the glands of salivary secretion, sebaceous secretion and lymph nodules. Smoothly, this layer flows into the submucosa. It is converted into loose connective tissue containing the smallest glands of salivary secretion and blood vessels of the hematopoietic system.

The submucosa contains a type of fat cells that are responsible for the ability to move. This layer is characteristic of the sections that are not subject to keratinization - the floor of the mouth, cheeks and lips.

Innervation of the oral cavity

The inner lining of the mouth is riddled with a huge number of nerve endings and fibers. Thanks to them, nerve impulses are transmitted to the central parts of the brain. The sensory function of the mouth allows a person to feel the taste, shape, temperature of external stimuli.

All the fibers along which the impulses go are connected to the main nerves of the oral surface:

• trigeminal nerve;
• facial nerve;
• glossopharyngeal nerve;
• nervus vagus.

The structure and direction of nerve fibers is similar to the trunks of blood vessels. The fibers are located in the mucous layer and are complexly intertwined with each other, form the endings of the nerves.

Some of them go to the papillary processes and connect to the epithelial layer, some of them combine with the cells above and go to the upper edge. Such a complex network of fibers and nerve endings covers the entire structure of the coating on all its layers.

The complex system of nerve endings allows the oral cavity to have a very strong sensitivity and respond to the slightest irritation. It is a unique organ of the human body through which it learns the world around it.

Blood supply and lymph drainage

The shell is equipped with an abundance of blood vessels. They look like arteries that are located in the submucosal layer and run parallel to the mucous layer. Arteries branch out processes perpendicular to the mucous layer. Most of the processes are present in the papilla layer and are very densely intertwined near the epithelium.

Capillaries differ in their structure depending on the location. The capillaries of the bottom of the mucous membrane and the gums have fenestrated epithelium, and the lining on the cheeks is a continuous flow. The vessels located along the venous bed are similar to the main arteries.

The cavity is also equipped with lymph drainage. The vessels of the lymphatic system begin with small capillaries with a wide lumen. They are located at the papillae connecting the mucous and epithelial layers. Gradually, the lymph capillaries combine into vessels and are directed similarly to blood vessels. The junction points of all vessels are the lymph nodes. All lymph from the membrane is transferred to the submandibular or cervical lymph node.

The blood supply system is highly developed in the mouth. This allows it to quickly regenerate and renew keratinized particles. Thanks to good blood flow, the mouth covering can perform functions such as protection, absorption, and immunity support.

The structure of the oral cavity

Let us consider in detail each component of the oral cavity, its structure, purpose and function.

Lip

Lips are circular muscles. Their outer side is covered with skin, and the inner side is covered with mucous membranes. A border with a transitional structure passes between the two sides. It lacks sweat glands and hair, but has salivary glands. Such a border is a characteristic feature of humans, unlike other animals.

Submucosal layer of the mucous part lips tightly connected to muscle fibers. Thanks to this, the lips are very smooth and wrinkle-free. The mucous membrane of the lips contains a large number of salivary glands. It mixes tightly with the epithelial layer by many blood capillaries, which are located near the surface and are practically invisible through it. This explains the color red. lips.

The labial mucosa is similar to the oral cavity. This part is not adapted to keratinization. Sebaceous glands are practically not found here and salivary glands predominate. They have a complex structure in the form of tubes, and secrete a more slimy secret.

In small children, the lips are relatively thicker, but at the same time they have a thinner epithelial cover. The main features and structure of the lips develop gradually, and this process ends by about 16 years of age. In the process of growing up of the body, changes in the structure of the lips also appear. The papillae between the layers are smoothed out, the collagen fibers become thinner and a lot of adipose tissue is formed in the submucosal layer.

The lips are equipped with many nerve endings. This makes the lips very sensitive. There are bridles on the upper and lower sides of the lips. These frenulums include collagen and elastic fibers. When close to the gums, the frenum can affect the mobility of the teeth and contribute to their displacement.

Cheek

The buccal covering is similar in structure to the oral membrane and serves as its continuation. It contains a thick epithelial layer that is not capable of keratinizing. The mucous membrane is formed by dense connective tissue with elastic fibers. This layer gradually flows into the submucosa and is tightly attached to the muscle fibers on cheeks.

The presence of elastic fibers in its composition, as well as a strong connection with muscle fibers, allows the surface of the cheeks to have the ability to be smooth and elastic. The submucous layer contains adipose tissue and small salivary glands. Fat deposits and glands can form clumps that can be mistaken for a tumor.

When viewed, the cover on the cheeks and lips has a fairly flat surface. But upon closer inspection, several characteristic properties can be seen. On the side, in the region of the second molar, on top, there is a papilla with an opening through which saliva flows from the parotid salivary gland. In the center of the upper and lower lips, there are folds or bridles that serve as the border for the right and left halves of the mouth.

At the level where the teeth meet, the mucous membrane of the cheeks is slightly different from the rest of the areas. There are no salivary glands, but the sebaceous glands are present and the epithelial cover is able to become keratinized. In infants, after birth, this part is covered with villi, like the villi on a red border.

The cheeks are well supplied with blood. The blood flow is due to the small salivary glands and cells. The mucous membrane of the cheeks contains a network of small blood vessels that are densely intertwined and supply blood to the cheeks.

Solid sky

The surface of the hard palate in some areas does not have the ability to move. This is due to the fact that in these departments it is tightly fused with the palatine bones. The submucosal layer is also absent in these places.

Among the fixed areas are:

• department of adherence to the tooth or marginal zone;
• department in the area of ​​the suture in the palate, where the mucous membrane is fused with the periosteum.

In other areas of the hard palate, there is a submucosal layer. In the areas in front there is adipose tissue, and in the distant areas there are a large number of small salivary glands.

The entire area of ​​the hard palate is divided into 4 sections:

• fatty;
• glandular;
• seam area;
• edge zone.

The mucous layer is expressed by connective tissue with the presence of collagen fibers. It is all covered with an epithelial layer with many layers and with the ability to harden and exfoliate scales. The connection of the mucous and epithelial layers occurs with the help of high papillae with sharp tips.

The area of ​​the hard palate has several irregularities. There is a papilla near the incisors in the front at the seam at the front end. In this area, vessels and nerve fibers pass through the bone. There are also transverse stripes in the front seam section. They are quite clearly visible in small children, but as they grow up, they become smooth and barely noticeable.

The blood flow to the palate passes through the arteries. Through the papilla of the anterior incisors, blood flows to small branches in the mucous membrane, and then crumbles into capillaries in the submucosal layer. The capillaries then carry the blood back to the veins.

The area of ​​the hard palate in front is washed by blood from the incisal artery, similarly, the blood leaves through the incisal vein and the vein of the nasal cavity. There are a lot of lymph vessels through which lymph drainage is carried out. The hard palate is rich in nerve endings. The bulk of nerve fibers are present in the mucous membranes of the anterior region.

Soft sky

The soft palate looks like a fibrous plate, on which striated muscles and mucous membranes are fixed. It is covered with a shell on all sides. There is a small process on it - a tongue.

The surface of the palate and uvula from below is covered with a flat epithelial layer, which is not capable of keratinization. The mucous layer is formed by connective tissue. A large number of elastic fibers are present at the transition between the mucous and submucous layers. The submucosa of the soft palate contains the ends of many glands of salivary secretion, their tops pass through the open part of the mucosa.

The distant part of the soft palate extends to the nasopharynx and is covered with a multilayered epithelial layer, which is exclusive to the respiratory tract. In small children, a multi-row epithelium is also present on the distant part of the uvula. But with age, it is replaced by a multilayer one, and in an adult, the tongue is covered on all sides with an ordinary epithelial layer.

It is well supplied with blood by the many vessels of the circulatory system. The capillaries are located near the edge of the mucosa and cause the red color. Lymphatic drainage in the soft palate is due to the lymph nodules.

Gum

Gum - This is the area of ​​the oral membrane that covers the alveolar processes of the jaws and touches the teeth. It consists of a multi-layered epithelial membrane capable of keratinization. The process of keratinization occurs noticeably on the vestibular gum; on the oral side, parakeratosis very often occurs.

The mucous layer of the gums is very similar to the dermis of the skin. It consists of two layers:

• a layer of papillae made of loose connective tissue;
• a layer in the form of a mesh, consisting of dense tissue and an abundance of collagen fibers.

The papillae have a complex structure, different shapes and sizes. In some parts, they form ramifications. It is along them that the main network of blood vessels of the circulatory system and the endings of the nervous system passes.

The submucosal layer and salivary glands are practically absent. The mucous membrane grows into the periosteum of the alveolar jaw processes. In the area of ​​the dental neck, fibers of the circular dental ligament grow into the mucous layer, and as a result, the gum is able to closely adhere to the teeth.

Plot gumsthat is fused with the periosteum is called the attached gum. The area of ​​the gum that lies freely near the tooth and is separated from it by a gap-like area is called the free gum.

The attached and loose gums are separated by a groove. It runs along the edge of the gum at a distance of 0.5-1.5 mm and characterizes the gingival gap. The area of ​​the gum between the teeth is called the interdental papilla. They are covered with stratified epithelium, but keratinization often turns into parakeratosis.

From the alveolar processes, the gum flows smoothly into the membrane covering the jaw. At the transition there is an uneven, loose epithelial cover. The surface of the jaws is further connected to the periosteum and flows into the folds of the lips or cheeks, the marginal zone of the hard palate or the oral floor.

The gingival gap is the distance between the tooth and the free edge of the gum. In a healthy state, the bottom of this gap reaches the level of the cervical enamel or the cement-enamel border. The epithelium in the gingival gap is firmly attached to the tooth. This site of attachment is called epithelial attachment.

This attachment plays a huge role in protecting the tissues around the tooth from various infections and environmental influences. As a result of the destruction of the epithelium of the gingival gap, the connective tissue is exposed, and the gap expands to the pocket. The epithelium begins to grow along the tooth root and the periodontal fibers are destroyed. This results in loosening and loss of teeth.

Language

Language is an organ made of muscles. It is surrounded by mucous membrane, which grows together with muscles in some parts.

On the dorsum above and on the surfaces on the sides, the submucosa is practically absent. It is in these parts that fusion with muscles occurs. language. The mucous membrane does not move here and does not form folds.

On a part of the tongue, a stratified epithelium is present on top, and characteristic protrusions are formed, called papillae. In their epithelium are taste buds. On the lower part, the stratified epithelium is smooth, does not undergo the process of keratinization, and has a characteristic submucosa.

The papillae of the tongue are divided into 4 types:

• in the form of threads;
• in the form of mushrooms;
• in the form of leaves;
• surrounded by a groove.

The filiform papillae are the most numerous. They are available on the entire lingual back. They are formed from the protrusions of the loose tissue of the mucous layer of the membrane. In addition, the growths entail a number of secondary protrusions, resembling thin villi. They are equipped with multiple peaks.

The epithelium on the papillae can become keratinized. Horny scales are characterized by a white color. The keratinization process is faster in the case of an increase in human body temperature and disturbances in the digestion process.

The mushroom-shaped protrusions are named for the owl's characteristic shape with a long base and a wide apex. They envelop the epithelium, which does not become keratinized. In them, vessels with blood pass very close to the surface. Therefore, the papillae in the form of mushrooms, when enlarged, look like red dots. They also contain taste buds.

Leaf-like - are parallel folds located on the tongue from the sides and have a separation with narrow grooves. Usually their number reaches 8 pieces with a length of up to 5 mm.

Such nipples are clearly visible in small children and some animals. The leaf-like projections are covered with epithelium and contain many taste buds. These bulbs are oval in shape and are composed of epithelial cells that are tightly connected to each other.

The main cells of the taste buds:

• sensorepithelial;
• supportive;
• basal;
• peripheral.

Microvilli depart from the sensoryepithelial cells and flow into the gustatory canal. This channel is presented on the surface of the epithelium in the form of a gustatory pore. There is a chemical between the villi that reacts to chemical compounds and affects nerve impulses. For each bulb of taste, there are more than fifty nerve fibers. On the part of the tongue in the front there are bulbs that recognize the sweet taste, on the back - the bitter one.

The latter type of papillae is grooved. They are located on the border between the main part of the language and its root. Their distinctive feature is that they are not visible on the surface of the tongue, but hidden in its depths.

All protrusions are surrounded by mucous membrane and separated from it by a deep furrow. This sulcus is where the protein glands from the muscle tissue at the base of the papillae drain. There are many taste bulbs in the epithelium around these protrusions.

The salivary glands are located in the tongue:

• mixed type in the anterior section;
• mucous secretion glands at the root of the tongue;
• glands of protein secretion on the border between the main part and the root of the tongue.

Blood flow in language provided by the lingual artery. They branch out into a dense network of capillaries. The venous vessels pass through the lower part of the tongue. Well developed lymph flow. It passes through the vessels through the lower surface of the tongue.

The lingual tonsil is a collection of nodules in the lymphatic system. It enters, along with other tonsils, into the lymphoepithelial ring, which protects the entire body. The amygdala is covered with non-keratinizing epithelium, which forms crypts or depressions. At the bottom of these depressions are the ducts of the lingual glands of salivary secretion.

Pathological processes

Various pathological processes can occur on the mucous membrane, they are all divided into the following types:

• inflammatory;
• tumor.

Inflammation is the body's response to the action of an external stimulus. It can be acute or chronic. By morphological characteristics, three forms can be distinguished:

• alternative;
• exudative;
• productive.

In the oral cavity, depending on the influencing factors, defects may occur:

1. Surface. In the form of erosion, when only the upper cover of the epithelium is damaged and the basal one is not affected. In such cases, a complete restoration of the surface after treatment is possible.
2. Deep. In the form of ulcers, they affect the epithelial and connective tissues of the oral cavity. After the treatment, the healing process takes place, but scars remain.

Any pathological processes affect the state of the oral surface. Changes occur here, which mainly affect the processes of keratinization of the epithelium.

Main pathologies:

1. Acanthosis characterized by an increase in the thickness of the epithelial layer as a result of the multiplication of basal cells and lengthening of the interpapillary processes. As a result, nodules may form. The reason for this phenomenon is such diseaseslike shingles, leukoplakia, lupus, cheilitis etc.
2. Parakeratosis - This is a phenomenon that manifests itself in incomplete keratinization of cells on the surface with the preservation of elongated nuclei in them. The sticky substance disappears from the cells, and as a result, the resulting scales are exfoliated. The cause may be diseases such as vitamin deficiency, leukoplakia, lichen, various forms of cheilitis, etc.
3. Disceratosis - This is a manifestation of improper keratinization, in which the pathology of keratinization is observed in individual cells. These cells are enlarged, rounded and have brightly colored nuclei. Then they take the form of homogeneous acidophilic formations with small granular nuclei and are located in the stratum corneum. Such manifestations are characteristic of Bowen's disease and squamous cell carcinoma.
4. Hyperkeratosis - This is the strongest increase in the thickness of the epithelial layer. This is due to the fact that keratin is formed in excess or exfoliation is delayed. The main reason for this phenomenon is the increased synthesis of keratin due to the increased activity of cells. Hyperkeratosis can occur due to the following diseases - leukoplakia, lichen, lupus, or cheilitis.
   

   Papillomatosis disease

5. Papillomatosis arises due to the fact that the papillary protrusions grow and grow into the epithelium. Basically, this phenomenon occurs due to chronic trauma to the palate with a prosthesis.
6. Vacuolar dystrophy - This is an internal edema of epithelial cells with the formation of decaying cells called vacuoles. The vacuole can occupy the entire space of the cell. The main causes of this pathological process are herpes and lupus.
7. Spongiosis consists in pathology when fluid accumulates between the cells of the styloid layer. At the beginning of the process, the tubules between the cells expand, which is filled with plasma, and then, with an increase in the amount of plasma, the bonds are broken and a cavity is formed. A blister or vesicle appears. This pathology occurs due to herpes, eczema, stomatitis, etc.
8. Ballooningdystrophy occurs as a result of a violation of cellular connections in the styloid layer. The reason for this is an increase in the thickness of the epithelium and the appearance of giant cells or their accumulation. In this case, the cell does not divide and floats in the plasma. This pathology manifests itself with herpes, erythema, lichen, etc.

The oral surface requires careful hygiene and periodic examinations for characteristic lesions. Any changes in the mouth are a manifestation of a disease.

Pathologies in the mouth can be the causes of such diseases:

• dental;
• venereal;
• skin diseases;
• violation in the metabolic processes of substances;
• diseases of internal organs;
• diseases of the circulatory system, etc.

Conclusion

The mucous membrane is a separate organ of the human body. It has several layers and covers the entire surface of the mouth. In different areas, the shell differs in its thickness and ability to keratinize.

The oral membrane is well supplied with blood and carries out lymph drainage. Nerve fibers are located in all its parts, thanks to which the entire surface has good sensitivity.

For various reasons, pathological changes are formed in the oral cavity. Their localization and the nature of the formations indicate the cause of the occurrence. Any changes require immediate treatment.