Sublingual gland histology drawing. Parotid gland: embryology, anatomy, histology and malformations

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 mucous membrane there are numerous small salivary glands: labial, buccal, lingual, palatine.

All salivary glands develop from ectoderm, like the stratified squamous epithelium lining the oral cavity. Therefore, the structure of their excretory ducts and secretory sections is characterized by multi-layering.

The salivary glands are complex alveolar or alveolar-tubular glands. They consist of terminal sections and ducts that remove secretions.

End sections (portio terminalis) according to the structure and nature of the secretion secreted, there are three types: proteinaceous (serous), mucous and mixed (i.e. proteinaceous and mucous).

Excretory ducts salivary glands are divided into intralobular ( ductus interlobularis), including intercalary ( ductus intercalates) and striated ( ductus striatus), interlobular ( ductus interlobularis) excretory ducts and gland ducts ( ductus excretorius seu glandulae).

Protein glands secrete a liquid secretion rich in enzymes. The mucous glands form a thicker, viscous secretion with a higher content mucin- a substance that contains glycoproteins. According to the mechanism for separating secretions from cells, all salivary glands merocrine(eccrine).

The salivary glands perform exocrine and endocrine functions. Exocrine function is the regular release into the oral cavity saliva. It consists of water (about 99%), protein substances, including enzymes, inorganic substances, as well as cellular elements (epithelial cells and leukocytes).

Saliva moistens food and gives it a semi-liquid consistency, which makes chewing and swallowing easier. Constant wetting of the mucous membrane of the cheeks and lips with saliva promotes the act of articulation. One of the important functions of saliva is the enzymatic processing of food. Salivary 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 the secretory function, the salivary glands perform an 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 is to secrete a bactericidal substance - lysozyme, as well as immunoglobulins class A.

The endocrine function of the salivary glands is ensured 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. The formation of the parotid glands occurs in 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. Numerous outgrowths bud from these cords, forming first the excretory ducts and then the terminal sections. At 10-12 weeks there is a system of branched epithelial cords and 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 secretion is mucous in nature. In the last months of development, fetal saliva exhibits amylolytic activity.

The submandibular glands are formed in the 6th week of embryogenesis. At week 8, gaps form in the epithelial cords. The epithelium of the primary excretory ducts is first two-layered, then multilayered. The terminal sections are formed at the 16th week. The mucous cells of the terminal sections are formed in the process of mucusing 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 cubic and prismatic shape, forming a protein secretion (Gianuzzi’s crescent). Secretion in the terminal sections begins in 4-month-old fetuses. The composition of the secretion differs from that of an adult. The sublingual glands are formed in the 8th week of embryogenesis in the form of processes from the oral ends of the submandibular glands. At the 12th week, budding and branching of the epithelial rudiment are noted.

Parotid glands

Parotid gland ( gl. parotis) is a complex alveolar branched gland that secretes protein secretion into the oral cavity and also has an endocrine function. On the outside it is covered with a dense connective tissue capsule. The gland has a pronounced lobular structure. In the layers of connective tissue between the lobules there are interlobular ducts and blood vessels.

Terminal parts of the parotid gland protein(serous). They consist of conical 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, the cell sizes increase significantly, and after secretion they decrease, the nucleus becomes rounded. The secretion of the parotid glands is dominated by a protein component, but often also contains mucopolysaccharides, so such glands can be called seromucous. The enzymes α-amylase and DNase are detected in secretory granules. Cytochemically and electron microscopically, several types of granules are distinguished - PAS-positive with an electron-dense rim, PAS-negative and 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 µm. Secretions are released from the cells into these tubules, which then enter 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) constitute the second layer of cells in the terminal secretory sections. By origin these are epithelial cells, by function they are contractile elements reminiscent of muscle cells. They are also called stellate epithelial cells, since they have a stellate shape and 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 release of secretions from the end sections.

Excretory duct system includes intercalary, striated, and interlobular ducts and the duct of the gland.

Intralobular intercalary ducts of the parotid gland begin directly from its terminal sections. They are usually highly branched. The intercalary ducts are lined with cubic or squamous epithelium. The second layer in them is formed by myoepitheliocytes. In the cells adjacent to the acini, electron-dense granules containing mucopolysaccharides are found; tonofilaments, ribosomes and agranular endoplasmic reticulum are also located here.

Striated The salivary ducts are a continuation of the intercalary ducts and are also located inside the lobules. Their diameter is much larger than the intercalary ducts, and the lumen is well defined. The striated ducts branch and often form ampullary extensions. They are lined with single-layer prismatic epithelium. The cytoplasm of the cells is acidophilic. In the apical part of the cells, microvilli, secretory granules with contents of varying electron density, and the Golgi apparatus are visible. In the basal parts of epithelial cells it is clearly visible basal striation, formed by mitochondria located in the cytoplasm between the folds of the cytolemma perpendicular to the basement membrane. In the striated sections, cyclical changes were revealed that were not associated with the rhythm of the digestive process.

Interlobular excretory ducts lined with double-layer 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 multilayer cubic epithelium, and at the mouth – with multilayer squamous epithelium.

Submandibular glands

Submandibular gland ( gll. submaxillare) is a complex alveolar (in some places alveolar-tubular) branched gland. The nature of the secretion is mixed, protein-mucous. The surface of the iron is surrounded by a connective tissue capsule.

The terminal secretory sections of the submandibular gland are of two types: protein and protein-mucosal, but the protein terminal sections predominate in it. Secretory granules of serocytes have a low electron density. Often the granules contain 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. The mixed terminal sections are larger than the proteinaceous ones and consist of two types of cells - mucous and proteinaceous. Mucus 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 mucous secretion in it. Small quantity protein cells covers mucous cells in the form serous crescent (semilunium serosum). The albuminous (serous) crescents of Giannuzzi are characteristic structures of mixed glands. Between the glandular cells there are intercellular secretory tubules. Outside the crescent cells lie myoepithelial cells.

Intercalary ducts the submandibular gland is less branched and shorter than in the parotid gland, which is explained by the mucusing of some of these sections during development. The cells of these sections contain small secretory granules, often with small dense cores.

Striated ducts in the submandibular gland they are very well developed, long and strongly branched. They often contain narrowing and balloon-like expansions. The prismatic epithelium lining them with well-defined basal striations contains a yellow pigment. Among the cells, electron microscopy distinguishes several types - wide dark, tall light, small triangular-shaped (poorly differentiated) and glass-shaped cells. In the basal part of tall cells, numerous cytoplasmic projections are located on the lateral surfaces. Some animals (rodents), in addition to striated ducts, have granular sections, the cells of which often have a well-developed Golgi apparatus, often located in their basal section, and granules containing trypsin-like proteases, as well as a number of hormonal and growth-stimulating factors. It has been established that the endocrine functions of the salivary glands (secretion of insulin-like and other substances) are associated with these departments.

The interlobular excretory ducts of the submandibular gland, located in the connective tissue septa, are lined first with double-layer and then multilayer epithelium. The duct of the submandibular gland opens next to the duct of the sublingual gland at the anterior edge of the frenulum of the tongue. Its mouth is lined with stratified squamous epithelium. The duct of the submandibular gland is more branched than the duct of the parotid gland.

Sublingual glands

Sublingual gland ( gl. sublinguale) is a complex alveolar-tubular branched gland. The nature of the secretion is mixed, mucous-protein, with a predominance of mucous secretion. It has three types of terminal secretory sections: protein, mixed and mucous.

The mixed terminal sections make up the bulk of the gland and consist of albuminous crescents And mucous cells. Crescent moons formed seromucous cells, they are better expressed than in the submandibular gland. The crescent-forming cells in the sublingual gland are significantly different from the corresponding cells in the parotid and submandibular glands. Their secretory granules react to mucin. These cells secrete both protein and mucous secretions and are therefore called seromucous cells. They have a highly developed granular endoplasmic reticulum. They are equipped with intercellular secretory tubules. The purely mucous terminal sections of this gland consist of characteristic mucous cells containing chondroitin sulfate B and glycoproteins. Myoepithelial elements form the outer layer in all types of end sections.

In the sublingual gland, the total area of ​​the intercalary ducts is very small, since during embryonic development they are almost completely mucused, forming the mucous parts of the terminal sections. The striated ducts in this gland are poorly developed: they are very short and in some places absent. These ducts are lined with prismatic or cuboidal epithelium, in which basal striations are also visible, as in the corresponding ducts of other salivary glands.

The cytoplasm of the epithelial cells lining the striated ducts contains small vesicles, which are considered as an indicator of excretion.

The intralobular and interlobular excretory ducts of the sublingual gland are formed by two-layer prismatic epithelium, and at the mouth - by multilayered squamous epithelium. The connective tissue intralobular and interlobular septa in these glands are better developed than in the parotid or submandibular glands.

Vascularization. All salivary glands are richly supplied with blood vessels. The arteries entering the glands accompany the branches of the excretory ducts. Branches extend from them, feeding the walls of the ducts. At the terminal sections, small arteries break up into a capillary network that densely entwines each of these sections. From the blood capillaries, the blood collects into the veins, which follow the course of the arteries.

The salivary glands are characterized by the presence of a significant amount arteriovenular anastomoses(AVA). They are located at the gate of the gland, at the entrance of the vessels into the lobule and in front of the capillary networks of the terminal sections. Anastomoses in the salivary glands make it possible to significantly change the intensity of blood supply to individual end sections, lobules and even the entire gland, and, consequently, changes in secretion in the salivary glands.

Innervation. Efferent, or secretory, fibers of the large salivary glands come from two sources: parts of the parasympathetic and sympathetic nervous systems. Histologically, myelinated and unmyelinated nerves are found in the glands, following the course of the vessels and ducts. They form nerve endings in the walls of blood vessels, at the end sections and in the excretory ducts of the glands. Morphological differences between secretory and vascular nerves cannot always be determined. In experiments on the submandibular gland of animals, it was shown that the involvement of sympathetic efferent pathways in the reflex leads to the formation of viscous saliva containing a large amount of mucus. When parasympathetic efferent pathways are irritated, a liquid protein secretion is formed. The closure and opening of the lumen of arteriovenular anastomoses and terminal veins is also determined by nerve impulses.

Age-related changes. After birth, the processes of morphogenesis in the parotid salivary glands continue until 16...20 years; in this case, glandular tissue predominates over connective tissue. After 40 years, involutive changes are observed, characterized by a decrease in the volume of glandular tissue, an increase in adipose tissue, and a strong proliferation of connective tissue. During the first 2 years of life, the parotid glands produce mainly a mucous secretion, from the 3rd year to old age - a protein secretion, and by the 80s, again a predominantly mucous secretion.

In the submandibular glands, the full development of the serous and mucous secretory sections is observed in 5-month-old children. The growth of the sublingual glands, like others, occurs most intensively during the first two years of life. Their maximum development is observed by the age of 25. After 50 years, involutional changes begin.

Regeneration. The functioning of the salivary glands is inevitably accompanied by partial destruction of epithelial glandular cells. Dying cells are characterized by large sizes, pyknotic nuclei and dense granular cytoplasm, strongly stained with acidic dyes. Such cells are called swelling. Restoration of the gland parenchyma is carried out mainly through intracellular regeneration and rare divisions of ductal cells.

Some terms from practical medicine:

• sialorrhea, syn.: ptyalism, hypersalivation(sialo-Greek. sialon saliva + Greek rhoia flow, outflow) - increased secretion of saliva of reduced viscosity;
• piggy, syn. mumps epidemic -- acute infectious disease caused by mumps virus transmitted by airborne droplets; characterized by inflammation of the parotid glands, less commonly

Besides many small salivary glands, located in the mucous membrane of the cheeks and glands of the tongue, in the oral cavity there are large salivary glands (parotid, submandibular and sublingual), which are derivatives of the epithelium of the oral mucosa. They are formed in the 2nd month of embryogenesis in the form of paired dense cords growing into the connective tissue. At the beginning of the 3rd month, a gap appears in the anlage of the glands.

From the free ends of the cords forging numerous outgrowths from which the alveolar or tubular-alveolar terminal sections are formed. Their epithelial lining is initially formed by poorly differentiated cells. Later, in the secretory department, as a result of divergent differentiation of the original cell, mucocytes (mucus cells) and serocytes (protein cells), as well as myoepitheliocytes, appear. Depending on the quantitative ratio of these cells, the nature of the secreted secretion and other structural and functional features, the terminal (secretory) sections are distinguished into three types: proteinaceous (serous), mucous (mucoid) and mixed (proteinaceous-mucoid).

As part of the output salivary gland tract distinguish intercalary and striated (or salivary tubes) sections of intralobular ducts, interlobular ducts, as well as the common excretory duct. According to the mechanism of secretion, all major salivary glands are merocrine. The salivary glands produce secretions that enter the oral cavity. In various glands, the secretory cycle, consisting of the phases of synthesis, accumulation and secretion, proceeds heterochronously. This causes continuous secretion of saliva.

Saliva is a mixture secretions of all salivary glands. It contains 99% water, salts, proteins, mucins, enzymes (amylase, maltase, lipase, peptidase, proteinase, etc.), a bactericidal substance - lysozyme and others. Saliva contains deflated epithelial cells, leukocytes, etc. Saliva moistens food, facilitates chewing and swallowing food, and also promotes articulation. The salivary glands perform an excretory function, releasing uric acid, creatinine, iron, etc. from the body. The endocrine function of the salivary glands is associated with the production of an insulin-like substance, nerve growth factor, epithelial growth factor and other biologically active compounds. A person secretes from 1 to 1.5 liters of saliva per day.

Salivation increases with stimulation of parasympathetic and decreases with stimulation of sympathetic nerve fibers.
Parotid glands. These are protein salivary glands, consisting of numerous lobules. In the lobules of the gland, there are terminal secretory sections (acini, or alveoli), intercalary ducts, and striated salivary tubes. In the terminal secretory sections, the epithelium is represented by two types of cells: serocytes and myoepitheliocytes. Serocytes have a cone shape with clearly defined apical and basal parts. The rounded nucleus occupies almost the middle position. In the basal part there are well-developed granular endoplasmic reticulum and the Golgi complex. This indicates a high level of protein synthesis in cells. In the apical part of serocytes, specific secretory granules containing amylase and some other enzymes are concentrated.

Between serocytes intercellular secretory tubules are revealed. Myoepithelial oocytes cover the acini like baskets and lie between the bases of the serocytes and the basement membrane. Their cytoplasm contains contractile filaments, the contraction of which promotes secretion.

Insertion departments excretory ducts begin directly from the terminal sections. They have a small diameter, are highly branched, and are lined with low cuboidal epithelium, among which there are poorly differentiated cambial cells. Here, as well as in the striated ducts, myoepitheliocytes are found. The striated ducts have a larger diameter, a wide lumen and are lined with columnar epithelium with pronounced oxyphilia of the cytoplasm. In the basal part of the cells, striations are revealed, due to the regular arrangement of mitochondria and deep folds of the plasmalemma. These cells transport water and ions. Endocrine cells - serotoninocytes - are found singly or in groups in the excretory ducts.

Submandibular glands. According to the composition of the secretion, these glands are classified as mixed. Their terminal secretory sections are of two types: protein and protein-mucosal. Protein acini predominate, arranged in the same way as in the parotid gland. The mixed terminal sections include serocytes, which make up the so-called serous crescents, and mucocytes. There are also myoepitheliocytes. Mucocytes appear lighter in color compared to serocytes. The nucleus in these cells lies at the base, it is flattened, and the mucous secretion occupies most of the cytoplasm. The insertion sections are short. Well-developed striated ducts. The cells of the striated ducts synthesize insulin-like factor and other biologically active substances.

Epithelium interlobular ducts gradually become multilayered as their caliber increases

Sublingual glands. These are alveolar tubular glands that produce a mucous-protein secretion with a predominance of mucoid. They have three types of secretory sections: protein, mucous and mixed. The main mass consists of mixed terminal sections formed by mucocytes and crescents of serocytes. The intercalary and striated ducts in the sublingual gland are poorly developed.

LECTURE 19: Salivary glands.

1. General characteristics. Functions.

2. Parotid salivary gland.

3. Submandibular salivary gland.

4. Sublingual salivary gland.

1. General characteristics. Functions.

The surface of the oral epithelium is constantly moistened by the secretion of the salivary glands (SG). There are a large number of salivary glands. There are small and large salivary glands. Small salivary glands are present in the lips, gums, cheeks, hard and soft palates, and in the thickness of the tongue. The large salivary glands include the parotid, submandibular and sublingual glands. Small SGs lie in the mucosa or submucosa, and large SGs lie outside these membranes. All SMs in the embryonic period develop from the epithelium of the oral cavity and mesenchyme. SG is characterized by an intracellular type of regeneration.

Functions of the SJ:

1. Exocrine function – secretion of saliva, which is necessary for:

Facilitates articulation;

Formation of a food bolus and its swallowing;

Cleaning the oral cavity from food debris;

Protection against microorganisms (lysozyme);

2. Endocrine function:

Production in small quantities of insulin, parotin, epithelial and nerve growth factors, and a lethality factor.

3. Beginning of enzymatic food processing (amylase, maltase, pepsinogen, nucleases).

4. Excretory function (uric acid, creatinine, iodine).

5. Participation in water-salt metabolism (1.0-1.5 l/day).

Let's take a closer look at large SGs. All large SGs develop from the epithelium of the oral cavity; they are all complex in structure (the excretory duct is highly branched. In large SGs, a terminal (secretory) section and excretory ducts are distinguished.

2. Parotid salivary glands.

The parotid gland is a complex alveolar protein gland. The terminal sections of the alveoli are proteinaceous in nature and consist of serocytes (protein cells). Serocytes are conical cells with basophilic cytoplasm. The apical part contains acidophilic secretory granules. Granular EPS, PC and mitochondria are well expressed in the cytoplasm. In the alveoli, myoepithelial cells are located outward from the serocytes (as if in a second layer). Myoepithelial cells have a stellate or branched shape, their processes encircle the terminal secretory section, and they contain contractile proteins in the cytoplasm. During contraction, myoepithelial cells promote the movement of secretions from the terminal section into the excretory ducts. The excretory ducts begin with intercalary ducts - they are lined with low cubic epithelial cells with basophilic cytoplasm, and are surrounded by myoepithelial cells from the outside. The intercalary ducts continue into the striated sections. The striated sections are lined with single-layer prismatic epithelium with basal striations, caused by the presence of cytolemma folds in the basal part of the cells and mitochondria lying in these folds. On the apical surface, epithelial cells have microvilli. The striated sections on the outside are also covered with myoepitheliocytes. In the striated sections, reabsorption of water from saliva (thickening of saliva) and balancing of the salt composition occurs, in addition, an endocrine function is attributed to this section. The striated sections, merging, continue into interlobular ducts, lined with 2-row epithelium, turning into 2-layer. The interlobular ducts flow into the common excretory duct, lined with stratified squamous non-keratinizing epithelium. The parotid SG is externally covered with a connective tissue capsule, interlobular septa are well defined, i.e. a clear lobulation of the organ is noted. In contrast to the submandibular and sublingual SG, in the parotid SG inside the lobules the PBST layer is poorly expressed.

3. Submandibular salivary gland.

The submandibular fluid is complex alveolar-tubular in structure, mixed in the nature of the secretion, i.e. mucous-protein (with a predominance of the protein component) gland. Most of the secretory sections are alveolar in structure, and the nature of the secretion is proteinaceous - the structure of these secretory sections is similar to the structure of the terminal sections of the parotid gland (see above). A smaller number of secretory sections are mixed - alveolar-tubular in structure, mucous-protein in the nature of the secretion. In the mixed terminal sections, large light mucocytes (poorly accepting dyes) are located in the center. They are surrounded in the form of crescents by smaller basophilic serocytes (protein crescents of Giuanzi). The terminal sections are surrounded on the outside by myoepitheliocytes. In the submandibular gland from the excretory ducts, the intercalary ducts are short, poorly defined, and the remaining sections have a similar structure to the parotid gland.

The stroma is represented by a capsule and SDT-tissue septa extending from it and layers of loose fibrous SDT. Compared to the parotid SG, the interlobular septa are less pronounced (weakly expressed lobulation). But inside the lobules, the PBST layers are better expressed.

4. Sublingual salivary gland.

The sublingual gland is a complex alveolar-tubular gland in structure; the nature of the secretion is mixed (muco-protein) gland with a predominance of the mucous component in the secretion. In the sublingual gland there are a small number of purely proteinaceous alveolar end sections (see description in the parotid gland), a significant number of mixed mucous-protein end sections (see description in the submandibular gland) and purely mucous secretory sections shaped like a tube and consisting of mucocytes with myoepitheliocytes. Among the features of the excretory ducts of the sublingual SG, the weak expression of the intercalary ducts and striated sections should be noted.

The sublingual SG, like the submandibular SG, is characterized by weakly expressed lobulation and well-defined PBST layers inside the lobules.

LECTURE 20: Respiratory system.

1. General morphofunctional characteristics of the respiratory system.

2. Evolution of the respiratory system.

3. Embryonic sources, formation and development of the respiratory system.

4. Age-related changes in the respiratory system.

5. Histological structure of the respiratory system.

1. General morphofunctional characteristics of the respiratory system.

The respiratory system performs the following functions:

1. Gas exchange (enrichment of blood with oxygen, release of carbon dioxide).

2. Participation in water-salt metabolism (water vapor in exhaled air).

3. Excretory function (mainly volatile substances, such as alcohol).

4. Blood depot (abundance of blood vessels).

5. Production of factors regulating blood clotting (in particular heparin and thromboplastin).

6. Participation in fat metabolism (burning fat using the released heat to warm the blood).

7. Participation in the sense of smell.

2. Evolution of the respiratory system.

Evolution of pulmonary respiration. The appearance of pulmonary respiration in the evolutionary ladder is associated with the exit of animals from the aquatic environment to land. Fish have gill breathing - water is constantly passed through the gill slits, oxygen dissolved in the water enriches the blood.

a) for the first time, pulmonary respiration appears in amphibians - and in them both pulmonary respiration and skin respiration exist in parallel. The lungs of amphibians are primitive and consist of 2 sac-like protrusions that open almost directly into the larynx, because trachea very short;

b) in reptiles, the respiratory sacs are divided by partitions into lobules and have a spongy appearance, the airways are more pronounced;

c) in birds - the bronchial tree is highly branched, the lungs are divided into segments. Birds have 5 air sacs - reserve reservoirs of inhaled air;

d) in mammals there is a further lengthening of the respiratory tract and an increase in the number of alveoli. In addition to the segments, lobes appear in the lungs and a diaphragm appears.

3. Embryonic sources, formation and development of the respiratory system.

Sources, formation and development of the respiratory system. The development of the respiratory system begins in the 3rd week of embryonic development. A blind protrusion is formed on the ventral wall of the anterior section of the first intestine (inside - the material of the prechordal plate, the middle layer - mesenchyme, outside - the visceral layer of splanchnotomes). This protrusion grows parallel to the first intestine, then the blind end of this protrusion begins to branch dichotomously. From the material of the prechordal plate are formed: the epithelium of the respiratory part and airways, the epithelium of glands in the walls of the airways; connective tissue elements and smooth muscle cells are formed from the surrounding mesenchyme; from the visceral layers of splanchnotomes - the visceral leaf of the pleura.

4. Age-related changes in the respiratory system.

By the time of birth, the number of lobes and segments basically corresponds to the number of these formations in adults. Before birth, the alveoli of the lungs remain in a collapsed state, lined with cubic or low-prismatic epithelium (i.e., the wall is thick), filled with tissue fluid mixed with amniotic fluid. With the first breath or cry of a child after birth, the alveoli straighten, fill with air, the wall of the alveoli stretches - the epithelium becomes flat. In a stillborn child, the alveoli remain in a collapsed state; under a microscope, the epithelium of the pulmonary alveoli is cubic or low-prismatic (if a piece of the lungs is thrown into water, they drown).

Further development of the respiratory system is due to an increase in the number and volume of alveoli and lengthening of the airways. By the age of 8, the volume of the lungs increases by 8 times compared to a newborn, by 12 years – by 10 times. From the age of 12, the lungs are close in external and internal structure to those of adults, but the slow development of the respiratory system continues until the age of 20-24.

After 70 years, involution is observed in the respiratory system:

The epithelium becomes thinner and thickens; basement membrane of the airway epithelium;

The glands of the airways begin to atrophy, their secretions thicken;

The number of smooth muscle cells in the walls of the airways decreases;

The cartilages of the airways become calcified;

The walls of the alveoli become thinner;

The elasticity of the walls of the alveoli decreases;

The walls of the respiratory bronchioles atrophy and become sclerotic.

5. Histological structure of the respiratory system.

The respiratory system consists of the airways (airways) and the respiratory section.

The airways include: the nasal cavity (with paranasal sinuses), nasopharynx, larynx, trachea, bronchi (large, medium and small), bronchioles (ending in terminal or terminal bronioles).

The nasal cavity is lined with multi-row ciliated epithelium; under the epithelium there is the own plastic mucous membrane made of loose fibrous connective tissue, where there are a large number of elastic fibers, a strongly pronounced plexus of blood vessels and the end sections of the mucous glands. The choroid plexus provides warmth to the passing air. Thanks to the presence of the olfactory epithelium on the nasal concha (see lecture “Sense Organs”), odors are sensed.

The larynx and trachea have a similar structure. They consist of 3 membranes - mucous membrane, fibrocartilaginous membrane and adventitial membrane.

I. The mucous membrane includes:

1. Multi-row ciliated epithelium (with the exception of the vocal cords, where there is multi-layered squamous non-keratinizing epithelium).

2. The lamina propria is made of loose fibrous connective tissue and contains mucous-protein glands. The trachea additionally has a submucous base of loose fibrous connective tissue with mucous-protein glands.

II. Fibrous-cartilaginous membrane - in the larynx: thyroid and cricoid cartilages from hyaline cartilage, sphenoid and cornicular cartilages from elastic cartilage; in the trachea: open cartilaginous rings of hyaline cartilage. Cartilage is covered with a fibrous layer of dense, irregular fibrous connective tissue.

III. The adventitia is made of loose fibrous connective tissue with vessels and nerve fibers.

The bronchi are divided into large, medium and small bronchi according to their caliber and histological structure.

Signs	Large bronchi	Middle bronchi	Small bronchi
Epithelium (general thickness< по мере < диаметра)	Single-layer multi-row ciliated (cl: ciliated, goblet-shaped, basal, endocrine)	Single-layer multi-row flickering (cl: the same)	Multi-row single-layer cylindrical/cubic (cl: the same + secretory (synthetic farm destruction surfactant) + border (chemoreceptors)
Myocyte count
Cartilaginous elements	Incomplete rings of hyaline cartilage	Small islands of elastic cartilage	No cartilage

Functions of air ducts:

Conducting (regulated!) air into the respiratory department;

Air conditioning (warming, humidification and cleaning);

Protective (lymphoid tissue, bactericidal properties of mucus);

Reception of smells.

The respiratory section includes respiratory bronchioles of order I, II and III, alveolar ducts, alveolar sacs and alveoli. Respiratory bronchioles are lined with cuboidal epithelium, the remaining membranes become thinner, individual myocytes remain, and along the way they have sparsely located alveoli. In the alveolar ducts, the wall becomes even thinner, myocytes disappear, and the number of alveoli increases. In the alveolar sacs, the wall consists entirely of alveoli. The set of all branches of one respiratory bronchiole is called the acinus, which is the morpho-functional unit of the respiratory department. Gas exchange in asinuts occurs through the walls of the alveoli.

Ultrastructure of the alveoli. Alveolus is a vesicle with a diameter of 120-140 microns. The inner surface of the alveoli is lined with 3 types of cells:

1. Respiratory epithelial cells (type I) are sharply flattened polygonal cells (the thickness of the cytoplasm in the non-nucleated areas is 0.2 µm, in the nuclear-containing part – up to 6 µm). The free surface has microvilli that increase the working surface. Function: gas exchange occurs through the thin cytoplasm of these cells.

2. Large (secretory) epithelial cells (type II) – cells of greater thickness; have many mitochondria, ER, lamellar complex and secretory granules with surfactant. Surfactant is a surfactant (reduces surface tension), forms a thin film on the surface of the epithelial cells lining the alveoli and has the following properties:

Reducing surface tension and preventing alveoli from collapsing;

Has bactericidal properties;

Facilitates the capture and transport of oxygen through the cytoplasm of respiratory epithelial cells;

Prevents the sweating of tissue fluid into the alveoli.

3. Pulmonary macrophages (type III) – formed from blood monocytes. The cells are motile and can form pseudopodia. The cytoplasm contains mitochondria and lysosomes. After phagocytosis, foreign particles or microorganisms move into the connective tissue layers between the alveoli and there they digest captured objects or die, forming “cemeteries” surrounded by a connective tissue capsule (examples: smoker’s lungs and miners’ lungs).

Respiratory epithelial cells and large epithelial cells are located on the basement membrane; the outside of the alveolus is entwined with elastic fibers and blood capillaries. Between the blood in the hemocapillaries entwining the alveoli and the air in the lumen of the alveoli there is an aerohematic barrier, which consists of the following elements:

Surfactant film;

Nuclear-free region of the cytoplasm of the respiratory epithelial cell;

Basement membrane of the alveoli and hemocapillary (merge!);

Nuclear-free region of the cytoplasm of the endotheliocyte of the hemocapillary.

The concept of interstitial tissue of the lungs is the tissue that fills the spaces between the bronchi and bronchioles, acini and alveoli. Histologically, it is a type of loose fibrous connective tissue, characterized by the following features:

1. In terms of cellular composition - unlike ordinary loose fibrous connective tissue, it contains more lymphocytes (they form lymphoid accumulations, especially along the bronchi and bronchioles - provide immune protection), a larger number of mast cells (synthesize heparin, histamine and thromboplastin - regulate blood clotting) , more macrophages.

2. According to the intercellular substance - contains a larger number of elastic fibers (provides a decrease in the volume of the alveoli during exhalation).

3. Blood supply - contains a very large number of hemocapillaries (gas exchange, blood depot).

LECTURE 21: Urinary system.

1. General characteristics, functions of the urinary system.

2. Sources, the principle of the structure of 3 successive buds in the embryonic period. Age-related changes in the histological structure of the kidneys.

3. Histological structure, histophysiology of the nephron.

4. Endocrine kidney function.

5. Regulation of kidney function.

1. General characteristics, functions of the urinary system.

As a result of metabolism in cells and tissues, energy is generated, but at the same time, end products of metabolism are also formed that are harmful to the body and must be removed. These wastes from the cells enter the blood. The gaseous part of the final products of metabolism, for example CO2, is removed through the lungs, and the products of protein metabolism through the kidneys. So, the main function of the kidneys is to remove metabolic end products from the body (excretory or excretory function). But the kidneys also perform other functions:

1. Participation in water-salt metabolism.

2. Participation in maintaining normal acid-base balance in the body.

3. Participation in the regulation of blood pressure (prostaglandins and renin hormones).

4. Participation in the regulation of erythrocytopoiesis (by the hormone erythropoietin).

2. Sources, the principle of the structure of 3 successive buds in the embryonic period. Age-related changes in the histological structure of the kidneys.

Sources of development, the principle of the structure of 3 consecutive buds.

In the embryonic period, 3 excretory organs are sequentially formed: the pronephros, the first kidney (mesonephros) and the final kidney (metanephros).

The preference is formed from the anterior 10 segmental legs. Segmental legs break off from the somites and turn into tubules - protonephridia; at the end of attachment to the splanchnotomes, the protonephridia open freely into the coelomic cavity (the cavity between the parietal and visceral leaves of the splanchnotomes), and the other ends connecting to form the mesonephric (Wolffian) duct flowing into the expanded section of the hindgut - the cloaca. The human adrenal duct does not function (an example of repetition of phylogeny in ontogenesis); soon the protonephridia undergo reverse development, but the mesonephric duct is preserved and participates in the formation of the first and final kidney and reproductive system.

The first kidney (mesonephros) is formed from the next 25 segmental legs located in the torso area. The segmental stalks break off from both the somites and the splanchnotomes and transform into the tubules of the first kidney (metanephridia). One end of the tubules ends in a blind vesicular extension. Branches from the aorta approach the blind end of the tubules and are pressed into it, turning the blind end of the metanephridia into a 2-walled glass - a renal corpuscle is formed. The other end of the tubules flows into the mesonephric (Wolffian) duct, which remains from the adrenal cortex. The first kidney functions and is the main excretory organ in the embryonic period. In the renal corpuscles, waste products are filtered from the blood into the tubules and enter through the Wolffian duct into the cloaca.

Subsequently, part of the tubules of the first kidney undergo reverse development, and part takes part in the formation of the reproductive system (in men). The mesonephric duct is preserved and takes part in the formation of the reproductive system.

The final bud is formed in the 2nd month of embryonic development from nephrogenic tissue (the unsegmented part of the mesoderm connecting the somites to the splanchnatoms), the mesonephric duct and mesenchyme. From nephrogenic tissue, renal tubules are formed, which, with their blind end, interacting with blood vessels, form renal corpuscles (see kidney I above); The tubules of the final kidney, in contrast to the tubules of the first kidney, are greatly elongated and successively form proximal convoluted tubules, the loop of Henle and distal convoluted tubules, i.e. The nephron epithelium is formed from nephrogenic tissue as a whole. Towards the distal convoluted tubules of the final kidney, a protrusion of the wall of the Wolffian duct grows, from its lower section the epithelium of the ureter, pelvis, renal calyces, papillary tubules and collecting ducts are formed.

In addition to nephrogenic tissue and the Wolffian duct, the formation of the urinary system involves:

1. The transitional epithelium of the bladder is formed from the endoderm of the allantois (the urinary sac is a protrusion of the endoderm of the posterior end of the first intestine) and ectoderm.

2. The epithelium of the urethra is from the ectoderm.

3. From mesenchyme - connective tissue and smooth muscle elements of the entire urinary system.

4. From the visceral layer of splanchnotomes - mesothelium of the peritoneal covering of the kidneys and bladder.

Age-related features of the kidney structure:

In newborns: in the preparation there are a lot of renal corpuscles located close to each other, the renal tubules are short, the cortex is relatively thin;

In a 5-year-old child: the number of renal corpuscles in the field of view decreases (diverge from each other due to an increase in the length of the renal tubules; but there are fewer tubules and their diameter is smaller than in adults;

By the time of puberty: the histological picture does not differ from adults.

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They are exocrine glands of ectodermal origin. They develop on the basis of the multilayered epithelium of the oral mucosa invaginating into the underlying mesenchyme. Divided into two groups:

1. intraorgan (small) - localized in the mucous membrane of the oral organs: labial, buccal, palatal, lingual;

2. extraorganic (large) - located outside the oral cavity, but connected to it by the excretory duct. They include three pairs of large salivary glands: parotid, submandibular and sublingual.

GENERAL PRINCIPLES OF THE STRUCTURE OF THE MAJOR SALIVARY GLANDS.

All major salivary glands are complex, branched in structure, alveolar (parotid) or alveolar-tubular (submandibular and sublingual) glands.

On the outside, the salivary glands are covered with a connective tissue capsule, from which septa extend deep into the organ, dividing it into lobules.

The STROMA of each lobule is formed by loose fibrous unformed connective tissue, in which vessels and nerves pass. Connective tissue contains accumulations of fat cells and numerous plasma cells that produce IgA.

The parenchyma of the glands is formed by ectodermal epithelium, which forms the terminal (secretory) sections and the system of excretory ducts.

The terminal sections consist of glandular epithelial cells of a prismatic shape and myoepithelial flattened cells lying outside the secretory ones.

Glandular cells synthesize, accumulate and secrete secretions; secretion is excreted according to the merokine type.

After the end of secretion, the process is repeated many times, which is why it is called the secretory cycle. Depending on the stage of the secretory cycle, the glandular cell has a different structure.

Based on the composition of glandular cells and the biochemical nature of the secretion, three types of secretory sections are distinguished:

1. Protein (serous) secretory sections contain cells that produce secretions of a protein nature - serocytes. These are prismatic cells with a basophilic coloration of the cytoplasm, with a well-developed synthetic apparatus, large secretory granules in the apical part of the cell. Serocytes produce liquid saliva with a high content of amylase, maltase, peroxidase, glycosaminoglycans and salts. Serocytes also synthesize a glycoprotein that binds and ensures the transfer and release into saliva of IgA produced by the plasma cells of the connective tissue surrounding the terminal sections. The protein secretory sections are small, round in shape, the central lumen in them is poorly distinguishable, and is colored basophilic.

2. The mucous end sections consist of mucous cells - mucocytes.

These are light cells with flattened nuclei located in the basal part. The apical and entire supranuclear part of the mucocytes contains mucous light granules. Mucocytes produce the mucous component of saliva containing glycoproteins and mucins. The mucous secretory sections are light, translucent, larger in size than the protein sections, and may have an irregular shape. They do not have basophilia, the central lumen in them is not visible on preparations.

3. Mixed terminal sections consist of two types of secretory cells - serocytes and mucocytes. The central, main in size, part of the terminal section is formed by mucocytes. The peripheral, marginal zone is surrounded by serocytes arranged in groups in the form of crescents (protein crescents of Gianuzzi). The mixed secretory sections are larger in size than the protein or mucous sections and have an irregular shape.

In all terminal sections, exocrinocytes are surrounded on the outside by myoepithelial cells, which are modified epithelial cells and contain numerous actin myofilaments. Myoepitheliocytes are flattened, have a stellate shape and are located between the basement membrane and the basal pole of glandular cells, covering the latter with their cytoplasmic processes. Myoepithelial cells have the ability to contract, which contributes to the removal of secretions from the end sections into the system of excretory ducts.

EXCRETORY DUCTS of the salivary glands form a system of confluent tubes, among which there are: intralobular ducts - intercalated and striated, interlobular ducts and the common excretory duct.

1) Intercalated excretory ducts begin from the terminal sections and flow into the striated ducts. They are represented by narrow tubes lined with cubic or flattened epithelial cells with poorly developed organelles. In the apical part of these cells, dense granules containing mucoid secretion may be found. Outside of the described epithelial cells in the wall of the intercalary ducts there are myoepithelial cells and cambial elements; due to the latter, the cells of the terminal sections and the system of excretory ducts are regenerated.

2) Striated ducts (salivary tubes) are located between the intercalary and interlobular ducts. They are represented by wide tubes with a well-defined central lumen. They are lined with oxyphilic colored tall prismatic epithelial cells with a rounded centrally located nucleus. These cells are secretory: granules containing kallikrein, an enzyme that breaks down blood plasma substrates, accumulate in their apical part, producing kinins that increase blood flow.

In the basal part of the cells, the cytoplasmic membrane forms deep, densely lying invaginations, in which elongated mitochondria are located in columns. This feature of the basal part of epithelial cells at the light-optical level creates a picture of “basal striation,” which gave rise to the name of the described ducts as striated.

The plasmalemma in the region of basal striation is involved in the transport of water and the reabsorption of Na from saliva. Potassium and bicarbonate ions are actively secreted into saliva, as a result of which the concentration of Na and Cl in it is 8 times lower, and K is 7 times higher than in blood plasma. Thus, the basal striation apparatus is related to the dilution and concentration of saliva.

In addition, the epithelial cells of the intralobular ducts (intercalated and striated), as well as the serocytes of the terminal sections, form a glycoprotein that ensures the transport of secretory IgA into saliva.

3) Interlobular ducts - located in the interlobular connective tissue. They are formed by the fusion of striated intralobular ducts, and their distal ends are combined into a common excretory duct. Among the interlobular ducts there are small and larger ones in diameter. The former are lined with single-row, and the latter with multi-row prismatic or double-layer epithelium.

4) Common excretory duct - has different lengths in different salivary glands.

In the initial part it is composed of multilayered prismatic epithelium, and closer to the mouth - multilayered squamous non-keratinizing epithelium.

STRUCTURE FEATURES OF INDIVIDUAL SALIVARY GLANDS.

PAROTICAL GLAND. It is a complex, branched alveolar gland. It has a thin, dense connective tissue capsule. It produces only protein secretion, therefore it contains only protein end sections: small, round with a small gap in the center. The intercalary ducts are highly branched. Well-developed striated ducts.

THE SUBMANDIBLE GLAND is a complex, branched, alveolar-tubular gland with a secretion of mixed chemical composition. Along with protein saliva, it forms mucus, therefore, in addition to the protein secretory sections, which are numerically predominant in the gland, it contains mixed terminal sections. As a result, the submandibular gland is mixed in the nature of the secretion produced, with a predominance of the protein component, i.e. protein-mucous.

The intercalary ducts in the submandibular gland are short, and the striated ducts are long and highly branched. The latter have expanded and narrowed areas.

THE SUBGLUSAL SALIVARY GLAND, like the submandibular one, is complex, branched, alveolar-tubular in structure, and mixed in the chemical composition of the secretion. The connective tissue capsule is poorly developed. The interlobular septa are developed much more strongly than in other glands.

Contains all three types of end sections, among which mixed and purely mucous end sections predominate. It contains little protein secretory sections, which is why it is called mucoprotein.

In the mixed terminal sections of the sublingual gland, the protein crescents are more developed than in the submandibular gland, but serocytes, in addition to protein secretion, also contain mucins; Therefore, such cells are called seromucous.

Different types of end sections are located unevenly in the gland: some parts of the organ may contain only mucous secretory sections, while others are predominantly mixed.

The intercalary ducts of the sublingual salivary gland are poorly developed, and the striated ones are very short.

The combined secretion of all salivary glands secreted into the oral cavity is called saliva. The parotid gland produces the thinnest saliva, and the sublingual gland produces the most viscous. Daily saliva volume of an adult

ranges from 0.5 to 2 liters. Approximately 25% of daily volume

saliva is produced by the parotid glands, 70% by the submandibular glands and 5% by the

activity of the sublingual and small salivary glands. Saliva secretion rate

also uneven throughout the day: when awake (outside of meals)

it is about 0.5 ml/min., during sleep - 0.05 ml/min., and during

stimulation of salivation reaches 2 or more ml/min.

Saliva has a micellar structure; it contains about 99% water and 1% organic (enzymes, proteoglycans, immunoglobulins) and inorganic (ions Ca, P, Na, K, Cl, etc.) substances, as well as salivary corpuscles - desquamated epithelial cells of the glands . Saliva has a neutral reaction (pH = 6.5-7.5).

At the same time, in the oral cavity, food particles, decaying mucosal cells, leukocyte cells, microflora of the oral cavity and soft dental plaque, and the contents of gingival pockets are mixed with the pure secretion of the salivary glands. The resulting mixed secretion of saliva and oral contents is called ORAL FLUID.

Functions of the salivary glands.

1. Digestive - saliva is involved in the processes of mechanical processing of food, the formation of a food bolus and its swallowing; promotes the taste perception of food and the formation of appetite; carries out chemical processing of food, breaking down polysaccharides (amylase).

2. Protective - protects the mucous membranes from mechanical damage from rough food, and its constant current prevents the attachment of pathogenic microorganisms to the surface of the epithelium and teeth; contains high concentrations of antimicrobial substances (lysozyme, lactoferrin, peroxidase); participates in immunological defense (secretory IgA).

3. Excretory - release from the body of metabolic products (uric acid, creatinine), pharmacological drugs, salts of heavy metals.

4. Regulation of water-salt homeostasis - release of fluid containing Na, K, Ca, Cl ions, etc.

5. Endocrine - production of hormonally active substances and growth factors (parotin, nerve growth factor, epidermal growth factor, etc.).

6. Mineralizing function - saliva is the main source of calcium, phosphorus and other minerals entering the tooth enamel, which affects the physical and chemical properties of tooth enamel, including resistance to caries.

Saliva is the most important factor in the homeostasis of mineral components in the oral cavity. The basis of the mineralizing function of saliva are mechanisms that prevent the demineralization of tooth enamel and promote the flow of minerals from saliva into the enamel. The balance of the mineral composition of enamel and saliva is maintained due to the balance between the dissolution of enamel hydroxyapatite crystals and their formation.

Under normal physiological conditions, hydroxyapatite [Ca10(H2PO4)2.H2O] is a solid compound of calcium (Ca) and phosphate (HPO). Its solubility depends on several conditions:

Active concentration of Ca and HPO4 ions;

Saliva pH;

Ionic strength of biological tissues and liquids.

The content of calcium, phosphates and carbonates in saliva depends on the activity of the salivary glands, which transport these mineral components into saliva. From 55% to 87% of calcium found in saliva is in ionized form, capable of ultrafiltration, the rest is in a bound state (bound by amylase, mucin, glycoproteins). Inorganic phosphate in saliva is in the form of orthophosphate and pyrophosphate, 95% of which are capable of ultrafiltration, and 5% are associated with proteins. The level of secretion of calcium and phosphates is at a constant level throughout the day, which ensures the constancy of these mineral components for physical and chemical exchange in the enamel.

The main mechanism for maintaining the homeostasis of mineral metabolism in the oral cavity is the state of saliva oversaturation with calcium and phosphate ions compared to the enamel. As a result, the increased concentration of these ions in saliva promotes their adsorption on the enamel surface and subsequent diffusion into the enamel along a concentration gradient with the formation of hydroxyapatite crystals. That is, the oversaturation of saliva with calcium and phosphate ions prevents the dissolution (demineralization) of enamel.

Unlike the submandibular and sublingual salivary glands, the saliva produced by the parotid gland is often undersaturated with calcium and phosphate ions, which is associated with more intense caries damage to the teeth of the upper jaw.

The mineralizing function of saliva is carried out most fully in a neutral environment, which is facilitated by the pH of saliva (normally fluctuates between 6.5 - 7.5). The oversaturation of saliva with ions persists up to pH = 6.0; with stronger acidification, saliva quickly becomes unsaturated with hydroxyapatite, leading to its rapid dissolution and losing its mineralizing properties. Alkalinization of the environment enhances the mineralizing properties of saliva, but at the same time promotes the formation of tartar.

A decrease in the functional activity of the salivary glands has a negative effect on the condition of the dentofacial apparatus, because:

The degree of washing of teeth with saliva decreases, which impairs cleansing of the oral cavity, washing out food debris, microflora, etc.;

Deterioration of self-cleaning of the oral cavity leads to a decrease in mineralization processes and a decrease in enamel resistance to demineralizing influences;

The intensity of antibacterial and immunological protective factors in the oral cavity decreases, which leads to the creation of favorable conditions for the development of microflora;

Digestion in the oral cavity worsens;

Homeostasis is disrupted.

SALIVARY GLANDS [glandulae oris(PNA, JNA, BNA); syn.: oral glands, T.] - digestive glands that secrete into the oral cavity a specific secretion that is part of saliva. There are large - parotid, submandibular, sublingual and small salivary glands - buccal, molar, labial, lingual of the hard and soft palate (Fig. 1).

Comparative anatomy and embryology

In animals that live in water, the glands of the mouth are poorly developed and are represented by simple glands that produce mucus. In terrestrial animals, due to the need to moisturize the oral mucosa and wet food, S. more developed. Amphibians have mucous labial, palatine, lingual and premaxillary glands. In reptiles, in addition, sublingual glands appear; in birds, the sublingual and so-called glands are well developed. angular glands. In mammals (except cetaceans), in addition to numerous small S. zh. large S. g. appear, located outside the oral cavity.

In human embryogenesis, all glands of the mouth arise as a result of the ingrowth of cellular elements of multilayered squamous epithelium of the mucous membrane into the underlying mesenchyme. Malye S. zh. develop from the 3rd month of embryonic development, by the 5th month excretory ducts are formed, the glands begin to function. Large S. develop from epithelial strands growing into the underlying mesenchyme, which during the growth process divide and form branching ducts and terminal sections. The formation of the parotid gland occurs at the 6th week, the submandibular gland - at the end of the 6th week. embryonic development. At 7-8 weeks. Several anlages of the sublingual glands appear, from which independent glands are formed; their end sections are united by a common capsule and open into the oral cavity with 10-12 separate openings.

Topography, anatomy

Depending on the location and place of confluence of the excretory ducts of the S. g. They are divided into glands of the vestibule of the oral cavity and glands of the oral cavity itself. The first group includes the molar (gll. molares), buccal (gll. buccales) and labial (gll. labia-les) glands, as well as the parotid gland (see), the excretory duct opens into the vestibule of the oral cavity on the mucous membrane cheeks at the level of the upper second molar. The submandibular and sublingual glands, as well as the glands of the tongue (gll. linguales), hard and soft palate (gll. palatinae) belong to the glands of the oral cavity itself.

Large S. They are lobular formations that can be easily palpated from the oral mucosa (see Parotid gland, Submandibular gland, Sublingual gland).

Malye S. zh. have a diameter of 1 - 5 mm and are located in groups in the submucosa of the mouth (see Mouth, oral cavity). The largest number of small S. zh. located in the submucosa of the lips, hard and soft palate. Among the minor salivary glands of the tongue there are: Ebner's glands - branched tubular glands, the ducts of which open into the grooves of the circumvallate papillae and between the leaf-shaped papillae of the tongue; glands, the ducts of which open into the crypts of the lingual tonsil, as well as the anterior lingual gland (gl. lingualis ant.), which is a cluster of glands that open with 3-4 excretory ducts on the lower surface of the tongue and under it (nunova glands).

Histology

S. zh. They are branched glands consisting of terminal, or secretory, sections and excretory ducts. Each gland is covered with a connective tissue capsule with layers of connective tissue extending from it into the organ, into which blood vessels and nerves pass. These layers divide the gland into lobes and segments, the basis of which is formed by the branches of the small excretory (intralobular) duct, passing into the terminal (secretory) sections. Terminal sections of the s. consist of glandular, secretory cells (glandulocytes) and myoepithelial cells (myoepithelial cells) located outside them. Secretion is formed in glandulocytes. According to the nature of the secretion, they distinguish between protein or serous (parotid gland and Ebner's glands), mucous (for example, palatine glands) and mixed (submandibular, sublingual, buccal, anterior lingual, labial) glands. According to the mechanism of secretion secretion, the salivary glands belong to the merocrine glands (see Glands).

Glandulocytes have a conical shape with a pointed apex and an expanded base. Electron microscopic studies (see Electron microscopy) have shown that on the lateral and basal surfaces of glandulocytes, the plasmalemma forms protrusions, folds and invaginations into the cytoplasm. The lateral surfaces have desmosomes (see) and end plates that provide communication between cells. Microvilli are revealed at the apical edges, the number of which increases with increasing secretory activity of the gland. The cytoplasm contains a well-developed endoplasmic reticulum (see), ribosomes (see) and the Golgi complex (see Golgi complex).

The terminal sections of the protein (serous) veins. formed by conical or pyramidal-shaped glandulocytes with basophilic cytoplasm and rounded nuclei - the so-called. serocytes (serocytus). Between the serocytes there are thin intercellular secretory tubules that do not have their own walls, which are a continuation of the cavity of the terminal sections.

The terminal sections of the mucous membranes of the S. g. formed by glandulocytes that have a very light, poorly stained cytoplasm with numerous vacuoles and a dark nucleus - the so-called. mucocytes (mucocytus. The secretion in mucocytes is formed in the form of mucinogen granules, which merge into a large drop of mucus occupying the apical part of the cell, the nuclei are shifted to the base of the cell and flattened.

In mixed glands, along with purely protein end sections, there are mixed sections, which include both mucous and protein cells. In this case, the central part of the mixed section is occupied by large light mucocytes, and darker serocytes lie along the periphery of the terminal section in the form of a crescent - the so-called. serous crescent, or Januzzi's crescent - semilima serosa (Fig. 2).

Myoepithelial cells (myoepithelial cells) are located on the basement membrane of the stomach. outwards from the glandulocytes, enveloping them with their cytoplasmic processes, the contraction of which promotes the removal of secretions from the end sections and its movement along the ducts. The terminal sections pass into intercalary ducts (ductus intercalati), lined with low cubic or squamous epithelium. They are well developed in the parotid gland, shorter in the submandibular gland and almost completely absent in the sublingual gland. Intercalated ducts pass into striated ducts (ductus striati), or Pfluger tubes, lined with high cubic epithelium, the cytoplasm of which has a characteristic striation. Electron microscopic examination reveals two types of cells here: dark and light (more numerous). The striated ducts are credited with the functions of removing secretions and participating in the processes of its concentration. There is evidence that the cells of the striated ducts take part in the production of hormone-like substances, in particular insulin-like protein. There are no striated ducts in the mucous glands. The intralobular excretory ducts continue into the interlobular ducts, lined with double-row epithelium, which, merging, form a common excretory duct, lined in the terminal section with multilayered squamous epithelium.

Blood supply of the s. carry out the branches of the external carotid arteries (see), blood flows into the system of the external and internal jugular veins (see). A feature of the circulatory system of the stomach. is the presence of numerous arteriovenular and arteriovenous anastomoses, through which blood from the arteries and arterioles enters the veins and venules, bypassing the capillary bed, which contributes to the redistribution of blood in the gland.

Lymph flows into the chin, submandibular and deep cervical lymph. nodes.

Parasympathetic innervation is carried out by the upper salivary nucleus of the facial and lower salivary nucleus of the glossopharyngeal nerves, sympathetic innervation by the external carotid plexus, in the formation of which the branches of the upper cervical ganglion of the sympathetic trunk take part.

Physiology

S. zh. secrete into the oral cavity through the excretory duct system a secret containing digestive enzymes: amylase, proteinase, lipase, etc. (see Salivation). The secretion of all S., mixed in the oral cavity, forms saliva (see), which ensures the formation of a food bolus and the beginning of digestion (see). There is information about the endocrine function of S. and their connections with the endocrine glands.

Pathological anatomy

Dystrophic changes in the stomach. often combined with a violation of their functions. Protein dystrophies (see Protein dystrophy) are characterized by cloudy swelling of glandular cells (granular dystrophy) and hyalinosis of interstitial tissue (see Hyalinosis). Granular degeneration of glandular cells is observed with sialadenitis (see), cachexia (see), as well as with poisoning with salts of heavy metals (mercury, lead, etc.), released with saliva and damaging glandular cells. Hyalinosis of the interstitial tissue leads to thickening of the interlobular septa; hyaline can be found in the walls of small vessels and in the basement membranes of the terminal (secretory) sections of the veins. With general amyloidosis (see), amyloid is occasionally deposited in the walls of blood vessels and basement membranes. Fatty degeneration of glandular cells (see Fatty degeneration) is observed in infectious diseases (diphtheria, tuberculosis) and chronic cardiovascular diseases. Lipomatosis S. is expressed in the growth between their lobules of adipose tissue (see Lipomatosis). Excessive development of adipose tissue in the thickness of the stomach. occurs in general obesity (see) and senile atrophy of the stomach.

Hypertrophy of the stomach. is a response to patol. processes occurring in the body. Increase in s. observed in endocrine diseases (eg, diffuse toxic goiter, hypothyroidism), liver cirrhosis and usually occurs as a result of reactive proliferation of interstitial tissue, which leads to interstitial sialadenitis. Hypertrophy of interstitial tissue is also observed in Mikulicz syndrome (see Mikulicz syndrome). In physiol. conditions of hypertrophy of the stomach. observed during pregnancy and the postpartum period. Sometimes, after removal of one of the paired glands, vicarious hypertrophy develops on the opposite side.

Atrophy of the s. characterized by a decrease in their size. Atrophic changes are observed when the innervation of the gland is disrupted, age-related involution, as well as when the outflow of gland secretions becomes difficult, followed by atrophy of the parenchyma. Histologically, there is a proliferation of connective tissue with thickening of the interlobular septa, a decrease in the size of glandulocytes, and emphasized lobulation of the sternum.

Postmortem changes in S. zh. occur early (after 3-4 hours), which is due to the self-digesting effect of salivary enzymes. Macroscopically, the glands acquire a reddish tint and soften. With pathohistol. The study reveals destructive changes in glandular cells, while interstitial tissue retains its structure much longer.

Examination methods include, in addition to general methods (questioning, examination, palpation, etc.), such special methods as probing of the ducts, sialometry (see Salivation), cytol. examination of secretions, ultrasonic dowsing (see Ultrasound diagnostics), thermovisiography (see Thermography), scanning (see), sialography (see), pantomography (see), pneumosubmandibulography (see), computer tomography (see cm.).

Pathology

Malformations of the stomach. are extremely rare, there are indications of dystopia, congenital absence and hypertrophy of the stomach. In the absence of all large S. xerostomia develops (see).

Damage large S. g. are noted when the parotid, submandibular, sublingual areas are injured. Trauma can lead to rupture of the parenchyma and ducts of the gland. Due to injury to S. a parenchymal defect, stenosis and atresia of the excretory duct, and salivary fistulas occur. Surgical treatment consists of forming the mouth of the duct in case of atresia, plastic closure of the salivary fistula (see Salivary fistulas). Salivary fistula of the parotid duct often recurs after surgery.

Diseases. Most often in S. zh. inflammatory processes develop. There are acute and chronic inflammation. The cause of acute inflammation of the stomach. there may be mumps viruses (see Epidemic mumps), influenza (see) or mixed bacterial flora that penetrates the gland during inf. diseases, after operations, especially on the abdominal cavity, by lymphogenous route or contact from phlegmonous foci in adjacent areas (see Mumps), as well as pathogens of tuberculosis (see), actinomycosis (see), syphilis (see). For acute inflammation of the stomach. characterized by the appearance of painful swelling in the corresponding area, disturbance of general health, increased body temperature, discharge of pus from the mouth of the duct, and abscess formation (Fig. 3).

Chron. inflammation occurs against the background of reactive-dystrophic changes in the stomach. Infectious agents invade the glands through ducts, lymphogenous or hematogenous routes. Chron. inflammation of the stomach may occur with the formation of stones in the ducts of the glands (see Sialolithiasis). The main signs hron. inflammation of the stomach are a long course of patol. process (years) with periodic exacerbations, swelling of the salivary glands and impaired salivary secretion.

Treatment of patients with acute and aggravated chronic conditions. inflammation of the stomach aimed at relieving acute phenomena with the help of medications. The opening of an abscess in the area of ​​the gland is carried out taking into account the anatomical features (see Parotid gland, Submandibular gland, Sublingual region). Measures are taken to restore the function of the gland. With chronic sialadenitis, treatment is indicated that increases the nonspecific resistance of the body, preventing exacerbation of the process (see Mumps, Sialadenitis). Removal of the gland is indicated if conservative treatment is unsuccessful. Treatment of actinomycosis, tuberculosis and syphilis S. carried out according to the rules adopted for these infections.

For various pathol. processes of a general nature: systemic diseases of connective tissue, diseases of the digestive system, nervous system, endocrine glands, etc., in S. zh. Reactive-dystrophic processes develop, which are expressed in an increase in the blood pressure. or disruption of their function. Treatment of reactive-dystrophic processes in the stomach. is aimed at improving the trophism of the gland, stimulating salivation, and eliminating the underlying disease. With systematic treatment, the process in the stomach. stabilizes, sometimes a decrease in the function of the stomach is possible. If necessary, anti-inflammatory therapy is carried out (novocaine blockade of the gland area, dimexide, etc.), as well as measures aimed at increasing the nonspecific resistance of the body.

Reactive processes in natural gas. during pregnancy and lactation, they are expressed in swelling of the glands, they are reversible and disappear after a certain period.

Tumors. Most tumors of S. has an epithelial origin, non-epithelial tumors make up no more than 2.5% of neoplasms of the stomach. Tumors develop predominantly in the large salivary glands: parotid and submandibular, and extremely rarely in the sublingual. The minor salivary glands are affected in approximately 12% of cases, and tumors can arise in any anatomical part of the oral cavity, but are most often localized on the hard palate, on the border of the soft and hard palate, in the area of ​​the alveolar process of the upper jaw.

The WHO International Histological Classification divides tumors of the salivary glands into 4 groups: epithelial (adenomas, mucoepidermoid tumors, acinar cell tumors, carcinomas), nonepithelial, unclassified tumors, related conditions (non-tumor diseases clinically similar to the tumor). In practice, it is advisable to distribute tumors according to the clinical and morphological principle. There are benign tumors, among which there are epithelial ones - polymorphic adenoma, or mixed tumor, adenolymphoma (see), oxyphilic adenoma, other types of adenomas (see Adenoma) and non-epithelial ones - hemangioma, lymphangioma, fibroma, neuroma, lipoma and etc.; locally destructive tumors (acinous cell tumor). Among malignant tumors, epithelial tumors are distinguished: mucoepidermoid tumor, cystadenoid carcinoma, or cylindroma, adenocarcinoma, epidermoid cancer, undifferentiated cancer and non-epithelial ones - sarcoma, lymphoreticular tumor, etc.; malignant tumors that developed in a mixed tumor (malignant polymorphic adenoma); secondary (metastatic) tumors.

Neoplasms of S. g. occur equally often in men and women over the age of 30 years.

Among benign epithelial neoplasms, more than 87% are polymorphic adenomas, or mixed tumors (see). Tumors of the g. usually located in the parenchyma, but can be superficial, sometimes the lesion is bilateral. A clinically benign tumor is a painless formation with a smooth or coarsely lumpy surface and a dense elastic consistency. Benign tumors have a well-defined capsule; only in a mixed tumor the capsule may be absent in certain areas; in this case, the tumor tissue is adjacent directly to the parenchyma of the gland. Usually the tumor is discovered by the patient himself when it reaches a size of 15-20 mm. If a tumor exists for a long time, its size can be significant.

Of the non-epithelial tumors, the most common are hemangioma (see) and lymphangioma (see). In most cases, they are detected already in early childhood in the form of a swelling that changes its shape and size when pressed and strained.

Acinous cell tumor is observed in approximately 1.6% of patients with tumors of the gastrointestinal tract, is localized in the parotid gland, clinically does not differ from benign tumors, signs of infiltrative growth are established only by microscopic examination.

For malignant tumors of S. Characterized by pain in the area of ​​the gland, infiltration of the skin over the tumor, regional and distant metastases.

Mucoepidermoid tumor (see) is localized mainly in the parotid gland and accounts for 2 to 12% of all tumors of the parotid gland. Wedge, the course largely depends on the degree of cell differentiation. Well, moderately and poorly differentiated tumors are distinguished. A well-differentiated mucoepidermoid tumor is difficult to distinguish clinically from a mixed tumor. A malignant course is observed in a third of patients.

Cystadenoid carcinoma, or cylindroma (see), accounts for up to 13% of neoplasms of the pancreas, and is found mainly in small pancreases, less often in large ones. There are three variants of tumor structure that determine the course of the disease: cribriform, characterized by a relatively long course, solid, characterized by a rapidly progressive course, and mixed, occupying an intermediate position in the clinical course. Wedge, manifestations of cystadenoid carcinoma in small S. determined by the localization of the process; in the parotid gland it manifests itself as a mixed tumor or is accompanied by pain and paralysis of the facial muscles. Unlike other malignant tumors, it is characterized by predominantly hematogenous metastasis. Metastases in regional lymph nodes are observed in 8-9% of cases.

Adenocarcinoma, epidermoid and undifferentiated cancer (see) are observed in 12% of patients with tumors of the stomach, and adenocarcinoma is more common than others. Two-thirds of these tumors arise in the parotid and submandibular glands. The process is progressive. The tumor is detected as a dense, painless node or infiltrate in the gland, without clear boundaries. Subsequently, moderate pain appears, which then becomes intense and radiating. An early symptom when the tumor is localized in the parotid gland is paralysis of the facial muscles. Infiltration quickly spreads to the tissues and organs surrounding the tumor, and regional metastases develop, usually on the affected side. Metastasis to distant organs is observed less frequently than with cylindrical oma.

Cancer in a mixed tumor occurs, according to various researchers, in up to 30% of cases. The longer mixed tumors exist, the greater the likelihood of their malignancy. In a mixed tumor, areas of invasive growth and cellular changes characteristic of cancer appear. Characteristic for a certain gistol develops. type of cancer wedge, picture. Because Tumors are usually large in size, but once infiltrative growth begins, they very quickly become inoperable.

Malignant non-epithelial tumors of S. are rare, mainly in the parotid gland. Clinically, they manifest themselves in the same way as other malignant tumors of the stomach, but at the same time they have all the properties of similar tumors of other localizations. With lymphoreticular tumor of the parotid gland, the facial nerve is not involved in the process.

In S. zh. metastases of malignant tumors of other localizations occur, most often melanoma and cancer of the skin of the face and head, oral cavity and upper respiratory tract.

Diagnosis of tumors of the stomach. includes a set of measures, the purpose of which is to determine the nature and degree of malignancy of the process. Preoperative diagnosis is based on clinical, cytological and radiological studies. The most reliable results are gistol. studies obtained from the study of biopsy or surgical material.

Treatment of tumors of the parotid gland is combined or surgical - see Parotid gland. Mixed acinar cell tumors of the submandibular gland are subject to surgical treatment - removal of the gland along with the submandibular fascial sheath (see Submandibular gland). Other benign tumors of the submandibular gland, as well as tumors of the sublingual and minor salivary glands, are enuclated; vascular tumors are sometimes preliminarily subjected to radiation therapy (see) in order to reduce their size.

Treatment of malignant tumors of S. combined. The first stage of treatment in the absence of metastases in regional lymph nodes includes preoperative (3-4 weeks before surgery) remote gamma therapy to the area of ​​the primary tumor in a total focal dose of 4000 rad (40 Gy), at the second stage an operation is performed - fascial sheath excision of the cervical tissue along with the tumor. For widespread tumors and relapses, resection of the lower jaw and excision of the tissues of the floor of the mouth are indicated. In case of metastases to cervical lymph nodes, the corresponding areas of the neck should be included in the irradiation zone. Malignant tumors of small sinuses, localized in the oral cavity and maxillary sinus, should be treated according to the same principle as cancer of these areas (see Paranasal sinuses; Mouth, oral cavity). In the absence of indications for radical surgical treatment, radiation therapy can be used.

Prognosis for benign tumors of the stomach. favorable. Relapses after treatment of mixed tumors are rare. Prognosis for malignant tumors of the stomach. adverse. Relapses and metastases to regional lymph nodes after using a combined treatment method occur in approximately 40-50% of patients. The five-year survival rate does not exceed 25%. The results of treatment of malignant tumors of the submandibular gland are significantly worse than those of the parotid gland.

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G. M. Mogilevsky (pat. an.), A. I. Paches, T. D. Tabolshuvskaya (onc.), I. F. Romacheva (pathology), G. S. Semenova (an., hist., embr.).