TONSILS
Tonsils— palatine and tubal (paired), lingual and pharyngeal (unpaired), forming the Pirogov-Waldeyer lymphoid pharyngeal ring, located in the area of the pharynx, root of the tongue and nasal pharynx. Tonsils are dense accumulations of lymphoid tissue containing small cellular masses - lymphoid nodules.
Lymphoid nodules present in many organs of the immune system. The stroma of the nodule consists of reticular cells and reticular fibers, forming a three-dimensional network, in the loops of which there are many lymphocytes.
Many lymphoid nodules have light centers of reproduction, surrounded by a darker rim of small lymphocytes 5-6 microns in size, closely adjacent to each other. In the centers of reproduction, lymphoblasts (about 12 µm in size) and medium-sized lymphocytes (about 8 µm in size) predominate, and mitotic figures are visible. Lymphoid nodules reach their maximum size by adolescence, their transverse size during this period reaches 1 mm. In children and adolescents, almost all lymphoid nodules have reproduction centers.
Palatine tonsil (tonsilla palati)na)- steam room, irregular in shape, located in the tonsillar fossa (bay), which is a depression between the palatoglossal and palatopharyngeal arches. The lateral side of the tonsil is adjacent to the connective tissue plate - the pharyngeal fascia, from which trabeculae (septa) extend medially into the lymphoid tissue of the organ.
On the medial free surface of the tonsil, up to 20 openings of the tonsil crypts, which are depressions of the mucous membrane, are visible. Some crypts have the shape of simply arranged tubes, others are branched deep into the amygdala. The mucous membrane is covered with stratified squamous non-keratinizing epithelium, which is infiltrated with lymphocytes.
In the diffuse lymphoid tissue of the tonsils there are dense accumulations of lymphoid tissue - lymphoid nodules (Fig. 101). The largest number of nodules is observed between the ages of 2 and 16 years.
Lymphoid nodules are located near the epithelial cover of the tonsil and near the crypts. In most lymphoid nodules, reproductive centers are visible. Around the nodules there is lymphoid tissue, which between the nodules looks like cellular strands up to 1.2 mm thick. The stroma of the tonsil is reticular tissue, the fibers of which form loops where lymphoid tissue cells are located. The connective tissue inside the palatine tonsil grows especially rapidly after 25-30 years, and the amount of lymphoid tissue decreases. After 40 years, lymphoid nodules in lymphoid tissue are rare, the size of the remaining nodules is relatively small (0.2-0.4 mm).
Blood supply palatine tonsil. The palatine tonsil is supplied by branches of the ascending pharyngeal artery, the facial artery (ascending palatine artery), as well as the descending palatine (from the maxillary artery) and lingual arteries. Venous blood flows into the veins of the pterygoid plexus.
Palatine tonsil innervated due to fibers of the greater palatine nerve (from the pterygopalatine ganglion), the tonsil branch of the glossopharyngeal nerve and sympathetic fibers from the internal carotid plexus.
Age-related features of the palatine tonsil. The palatine tonsils are formed at the 12-14th week of intrauterine development in the form of a cluster under the epithelium of the second pharyngeal pouch. In a 5-month-old fetus, the tonsil is represented by an accumulation of lymphoid tissue up to 2-3 mm in size. At this time, the forming amygdala begins to
Rice. 101. The structure of the palatine tonsil: 1 - mucous membrane; 2 - stratified squamous epithelium; 3 - lymphoid tissue of the tonsil; 4 - lymphoid nodules; 5 - lumen of the crypt (according to I.V. Alma-
I also call L. S. Sutulova)
epithelial strands grow in, future crypts form. At the 30th week, the crypts still do not have a lumen, and lymphoid tissue is located around the epithelial strands. By the time of birth, the amount of lymphoid tissue increases, individual lymphoid nodules appear without reproductive centers, which form after birth. During the 1st year of a child’s life, the size of the tonsils doubles (up to 15 mm in length and 12 mm in width), and by the age of 8-13 they are at their largest and remain this way until about 30 years. After 25-30 years, pronounced age-related involution of lymphoid tissue occurs. Along with a decrease in the mass of lymphoid tissue in the organ, there is a proliferation of connective tissue, which is already clearly noticeable at 17-24 years of age.
Lingual tonsil(tonsilla lingualis)- unpaired, lies in the lamina propria of the mucous membrane of the root of the tongue in the form of one or two accumulations of lymphoid tissue containing numerous lymphoid nodules. The mucous membrane above the tonsil has depressions - crypts, the walls of which are formed by multilayered squamous non-keratinizing epithelium infiltrated with lymphocytes.
Lingual tonsil is supplied with blood branches of the right and left lingual arteries. Venous blood from the tonsils flows into the lingual vein.
Lingual tonsil innervated fibers of the glossopharyngeal and vagus nerves, as well as sympathetic fibers of the external carotid plexus.
Age-related features of the lingual tonsil. The lingual tonsil appears in the 6-7th month of intrauterine development in the form of single diffuse accumulations of lymphoid tissue in the lateral sections of the root of the tongue. At the 8-9th month of fetal development, lymphoid tissue forms lymphoid nodules. At this time, small, irregularly shaped tubercles and folds are visible on the surface of the tongue root. By the time of birth, the number of lymphoid nodules in the tonsil increases. Soon after birth, reproductive centers appear in the lymphoid nodules. Subsequently, the number of lymphoid nodules increases until adolescence. In infants, there are an average of 66 nodules in the lingual tonsil. During early childhood, their number averages 85, and in adolescence - 90. The lingual tonsil reaches its largest size in children and adolescents. Starting from adolescence, the number of lymphoid nodules in the lingual tonsil gradually decreases. In old age and senility, the amount of lymphoid tissue in the lingual tonsil decreases, and connective tissue grows in it.
Pharyngeal tonsil(ttonsilla pharyngetalis)- unpaired, located in the area of the fornix and partly of the posterior wall of the pharynx between the pharyngeal openings of the right and left auditory tubes. In this place there are 4-6 transversely and obliquely oriented folds of the mucous membrane, separated by grooves, inside which is the lymphoid tissue of the pharyngeal tonsil. Between the folds in the grooves, the ducts of the glands open in the thickness of the folds. The free surface of the folds is covered with stratified squamous non-keratinizing epithelium; in the depths of the furrows there are areas of multi-row ciliated epithelium. Under the epithelium in the lamina propria of the mucous membrane there is diffuse lymphoid tissue and lymphoid nodules of the pharyngeal tonsil. The diameter of the nodules is 0.8 mm.
Pharyngeal tonsil is supplied with blood branches of the ascending pharyngeal artery. Venous blood flows into the veins of the pharyngeal plexus.
Amygdala innervated nerve fibers extending from the branches of the facial, glossopharyngeal, and vagus nerves. Sympathetic fibers originate from the periarterial plexuses.
Age-related features of the pharyngeal tonsil. The pharyngeal tonsil is formed in the 3-4th month of intrauterine life in the thickness of the developing mucous membrane of the nasal part of the pharynx. In a newborn, the tonsil is already well defined and measures 5-6 mm. Subsequently, the amygdala grows quite quickly. By the end of the year, its length reaches 12 mm and width - 6-10 mm. The tonsil reaches its largest size at 8-20 years of age, its length is 13-21 mm, and its width is 10-15 mm. Lymphoid nodules in the tonsil appear in the 1st year of life. After 30 years, the pharyngeal tonsil gradually decreases.
Tubal tonsil(tonsilla tubaria)- steam room, located in the area of the tubal ridge, which limits the pharyngeal opening of the auditory tube from behind. The tonsil is an accumulation of lymphoid tissue in the lamina propria of the mucous membrane of the auditory tube near its pharyngeal opening. The tonsil contains single round lymphoid nodules. The mucous membrane is covered with stratified squamous non-keratinizing epithelium.
The tubal tonsil begins to develop at the 7-8th month of intrauterine life in the thickness of the mucous membrane around the pharyngeal opening of the auditory tube. First, separate accumulations of future lymphoid tissue appear, from which the tubal tonsil is subsequently formed. The tubal tonsil is already expressed in a newborn, its length reaches 7-7.5 mm, and it reaches its greatest development at 4-7 years.
In children, small tubercles are visible on the surface of the mucous membrane in the area of the tubal tonsil, under which there are lymphoid nodules. Lymphoid nodules and reproductive centers in them appear in the 1st year of a child’s life. Age-related involution of the tubal tonsil begins in adolescence and young adulthood.
Tubal tonsil is supplied with blood branches of the ascending pharyngeal artery. Venous blood from the tonsil flows into the veins of the pharyngeal plexus.
Nerve fibers they enter the amygdala as part of the branches of the facial, glossopharyngeal and vagus nerves, as well as from the periarterial sympathetic plexuses.
At the border of the oral cavity and pharynx in the mucous membrane there are large accumulations of lymphoid tissue. Together they form a lymphoepithelial pharyngeal ring surrounding the entrance to the respiratory and digestive tracts. The largest clusters of this ring are called tonsils. Based on their location, the palatine tonsils, pharyngeal tonsil, and lingual tonsil are distinguished. In addition to the listed tonsils, in the mucous membrane of the anterior part of the digestive tube there are a number of accumulations of lymphoid tissue, of which the largest are the accumulations in the area of the auditory tubes - tubal tonsils and in the ventricle of the larynx - laryngeal tonsils. Tonsils perform an important protective function in the body, neutralizing microbes that constantly enter the body from the external environment through the nasal and oral openings. Along with other organs containing lymphoid tissue, they provide the formation of lymphocytes involved in the reactions of humoral and cellular immunity. Development. The palatine tonsils are formed in the 9th week of embryogenesis in the form of a depression in the pseudostratified ciliated epithelium of the lateral wall of the pharynx, under which lie compactly located mesenchymal cells and numerous blood vessels. At the 11-12th week, the tonsillar sinus is formed, the epithelium of which is reconstructed into a multilayered squamous one, and reticular tissue is differentiated from the mesenchyme; vessels appear, including postcapillary venules with high endothelial cells. The organ is populated with lymphocytes. At week 14, among the lymphocytes, mainly T-lymphocytes (21%) and a few B-lymphocytes (1%) are detected. At 17-18 weeks, the first lymph nodes appear. By the 19th week, the content of T-lymphocytes increases to 60%, and B-lymphocytes - to 3%. The growth of the epithelium is accompanied by the formation of plugs of keratinizing cells in the epithelial cords. The pharyngeal tonsil develops in the 4th month of the prenatal period from the epithelium and underlying mesenchyme of the dorsal wall of the pharynx. In the embryo, it is covered with multirow ciliated epithelium. The lingual tonsil develops in the 5th month. The tonsils reach their maximum development in childhood. The onset of tonsil involution coincides with puberty. Structure. The palatine tonsils in the adult body are represented by two oval-shaped bodies located on both sides of the pharynx between the palatine arches. Each tonsil consists of several folds of the mucous membrane, in the lamina propria of which there are numerous lymph nodes (noduli lymphathici). From the surface of the tonsil, 10–20 crypts (criptae tonsillares) extend deep into the organ, which branch and form secondary crypts. The mucous membrane is covered with stratified squamous non-keratinizing epithelium. In many places, especially in the crypts, the epithelium is often infiltrated (populated) with lymphocytes and granulocytes. Leukocytes that penetrate into the thickness of the epithelium usually come to its surface in greater or lesser numbers and migrate towards bacteria that enter the oral cavity along with food and air. Microbes in the tonsil are actively phagocytosed by leukocytes and macrophages, and some of the leukocytes die. Under the influence of microbes and various enzymes secreted by leukocytes, the epithelium of the tonsil is often destroyed. However, after some time, due to the proliferation of cells of the epithelial layer, these areas are restored. The lamina propria of the mucous membrane forms small papillae that protrude into the epithelium. The loose fibrous connective tissue of this layer contains numerous lymph nodes. In the centers of some nodules, lighter areas are clearly visible - germinative centers. Lymphoid nodules of the tonsils are most often separated from each other by thin layers of connective tissue. However, some nodules may merge. The muscular plate of the mucous membrane is not expressed. The submucosa, located under a cluster of lymphoid nodules, forms a capsule around the tonsil, from which connective tissue septa extend deep into the tonsil. This layer contains the main blood and lymphatic vessels of the tonsil and the branches of the glossopharyngeal nerve that innervate it. The secretory sections of the small salivary glands are also located here. The ducts of these glands open on the surface of the mucous membrane located around the tonsil. Outside the submucosa lie the striated muscles of the pharynx - an analogue of the muscular coat.
Pharyngeal tonsil located in the area of the dorsal wall of the pharynx, lying between the openings of the auditory tubes. Its structure is similar to other tonsils. In the adult body, it is lined with multilayered squamous non-keratinizing epithelium. However, in the crypts of the pharyngeal tonsil and in adults, areas of pseudostratified ciliated epithelium, characteristic of the embryonic period of development, are sometimes found. In some pathological conditions, the pharyngeal tonsil can be very enlarged (the so-called adenoids). The lingual tonsil is located in the mucous membrane of the root of the tongue. The epithelium covering the surface of the tonsil and lining the crypts is stratified squamous, non-keratinizing. The epithelium and the underlying lamina propria are infiltrated by lymphocytes penetrating here from the lymph nodes. At the bottom of many crypts, the excretory ducts of the salivary glands of the tongue open. Their secretion helps to wash and cleanse the crypts.
Salivary glands
General morphofunctional characteristics. The excretory ducts of three pairs of large salivary glands open into the oral cavity: parotid, submandibular and sublingual. In addition, in the thickness of the oral mucosa there are numerous small salivary glands: labial, buccal, lingual, palatine. The epithelial structures of all salivary glands develop from the ectoderm, as does the stratified squamous epithelium lining the oral cavity. Therefore, the structure of their excretory ducts and secretory sections is characterized by multilayering. The salivary glands are complex alveolar or alveolar-tubular glands. They consist of terminal sections and ducts that remove secretions. The terminal sections (portio terminalis), according to the structure and nature of the secreted secretion, are of three types: proteinaceous (serous), mucous and mixed (i.e. proteinaceous). The excretory ducts of the salivary glands are divided into intralobular (ductus interlobularis), including intercalates (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 of mucin, a substance that includes glycoproteins. According to the mechanism for separating secretions from cells, all salivary glands are merocrine. The salivary glands perform exocrine and endocrine functions. The exocrine function is the regular release of saliva into the oral cavity. 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 class A immunoglobulins. 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 at the 8th week of embryogenesis, when epithelial strands begin to grow from the epithelium of the oral cavity into the underlying mesenchyme towards the right and left ear openings. 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
The 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. The terminal sections of the parotid gland are proteinaceous (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 (myoepithelial cells) make up 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. The system of excretory ducts includes intercalary, striated, and interlobular ducts and the duct of the gland. The 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. The striated 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, basal striations formed by mitochondria located in the cytoplasm between the folds of the cytolemma perpendicular to the basement membrane are clearly visible. In the striated sections, cyclic changes were revealed that were not associated with the rhythm of the digestive process. The interlobular excretory ducts are 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. The duct of the parotid gland, starting in its 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
The 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. Mucous cells (mucocyti) are larger than protein cells 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. A small number of protein cells cover the mucous cells in the form of a 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. The intercalary ducts of the submandibular gland are less branched and shorter than those in the parotid gland, which is explained by the mucus formation of some of these sections during development. The cells of these sections contain small secretory granules, often with small dense cores. The striated ducts in the submandibular gland 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-layered and then multilayered 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. Protein terminal sections are very few in number. The mixed terminal sections make up the bulk of the gland and consist of protein crescents and mucous cells. The crescents formed by seromucous cells are better expressed in them 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 circulatory system of the salivary glands is characterized by the presence of a significant number of 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 the 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 cells. Restoration of the gland parenchyma is carried out mainly through intracellular regeneration and rare divisions of ductal cells.
The term " lymphoepithelial tissue"is used to emphasize the close symbiosis of epithelial and lymphoid cells (reticular epithelium).
Reticulohistiocytic system, which is more often called reticuloendothelial, with its accumulation cells is richly represented in lymphoepithelial tissue. The figure below shows a diagram of the structure of the lymphoepithelial unit. Solitary units of this type, solitary follicles, are found throughout the mucosa. The epithelium is also diffusely impregnated with lymphocytes.
Isolated accumulation of lymphoepithelial tissue, known as Waldeyer's ring, is located in the pharynx at the level of the auditory tube.
Lymphoepithelial organs are called tonsils. The following accumulations of lymphoepithelial tissue are distinguished:
1. Pharyngeal tonsil, or adenoid, a single accumulation of lymphoepithelial tissue located in the upper part of the posterior wall of the nasopharynx.
2. Tubal tonsil, a paired cluster located around the opening of the auditory tube in the Rosenmüllerian fossa.
3. Paired palatine tonsil, located between the anterior and posterior palatine arches.
4. Lingual tonsil, a single cluster located at the root of the tongue. Less common:
5. Tubal-pharyngeal folds, located laterally, which are oriented almost vertically at the transition of the lateral wall to the posterior wall in the oropharynx and nasopharynx.
6. Lymphoepithelial accumulations in the laryngeal ventricle.
1 - hard palate; 2 - palatine glands; 3 - palatine arteries and veins;
4 - muscles of the palatine curtain; 5 - palatoglossus muscle; 6 - palatoglossus arches;
7 - palatine tonsil; 8 - uvula; 9-language; 10-gum.
In contrast from the lymph nodes, lymphoepithelial organs have only efferent lymphatic vessels; they lack afferent ones. Differences in the pathology and physiology of individual lymphoid tissue accumulations are associated with differences in their structure. The figure below shows the structure of the tonsil and adenoids.
Fine structure tonsils characterized by the following features: the presence of soft tissue lamellae, or septa, extending from the basal connective tissue capsule and being a kind of supporting frame in which blood and lymphatic vessels and nerves pass.
Septas, diverging fan-shaped, significantly increase the active surface of the tonsil and serve as a supporting frame for the lymphoepithelial parenchyma. In the palatine tonsil, the active surface is immersed in the mucous membrane, while in the adenoids they protrude above the surface. Wide flat niches formed as a result of screwing in the septa and opening into the oral cavity are called lacunae, and branching cracks along the entire surface of the tonsil are called crypts.
Actually tonsil tissue consists of an accumulation of a very large number of lymphoepithelial units described above. Crypts usually contain remnants of non-viable tissue and round cells, as well as bacteria and fungal colonies, accumulations of pus and encapsulated microabscesses.
Tonsils, forming Waldeyer's pharyngeal lymphoid ring, are already found in the embryo, but they acquire a secondary, final structure, together with the lymph nodes, in the postnatal period, i.e. after direct contact with environmental pathogens. Tonsils begin to grow rapidly between the 1st and 3rd years of life and reach their maximum size between the 3rd and 7th years of life.
With the beginning puberty gradual involution of the tonsils begins. Like the rest of the lymphatic system, tonsils atrophy with age.
Arterial blood supply The pharyngeal tonsil is supplied by branches of the external carotid artery, including the facial and ascending palatine arteries, the ascending pharyngeal and lingual arteries, and possibly direct tonsillar branches.
Veins of the pharyngeal tonsil usually drain into the palatine vein, which in turn drains into the internal or its branch, the facial vein. The pterygoid venous plexus also participates in the drainage of venous blood, from which blood also flows into the internal jugular vein. Through this venous drainage pathway, infection from the tonsils can spread to the cavernous sinus.
Structure of lymphoepithelial tissue: 1 - flat epithelium; 2 - reticular epithelium; 3 - secondary nodes with light centers and dark zones of small lymphocytes;
4 - lymphoid tissue; 5 - arterioles and venules; 6 - postcapillary veins.
Nasopharyngeal tonsil and adenoids (a) and palatine tonsil (b): 1 - tonsillar lacunae; 2 - tonsillar crypts; 3 - cryptogenic abscess.
Video of the anatomy and composition of the Pirogov-Waldeyer lymphoepithelial ring (lymphoid ring of the pharynx)
If you have problems watching, download the video from the pageLymphoid ring (Pirogov–Waldeyer ring)– a complex of 6 pharyngeal tonsils.
Tonsilla lingualis(lingual)– a set of lymphoid follicles of the posterior part of the tongue.
Tonsilla palatina(palatines)– steam room, located in fossa tonsillaris, formed by arcus palatoglossus, and arcus palatopharyngeus. Surrounded by a fibrous capsule.
Tonsilla pharyngea(palatal/adenoids) - an accumulation of lymphoid tissue at the border between the upper and posterior walls of the pharynx, along the midline.
Tonsilla tubaria(pharyngeal)- a paired accumulation of lymphoid tissue between the pharyngeal opening of the tube and the soft palate.
That. at the entrance to the pharynx there is an almost complete ring of lymphoid formations: tonsil of the tongue, 2 palatines, 2 tubes and pharyngeal.
This organ requires a more detailed description. In addition to 4 tonsils, there are accumulations of adenoid tissue in the form of diffuse and limited formations scattered throughout the pharyngeal mucosa. These include the so-called grains of the posterior wall of the pharynx, the lateral ridges of the pharynx and similar formations in the area of the nasopharyngeal openings of the Eustachian tubes.
Palatine tonsils They represent great diversity in their shape and size. The outer surface of the palatine tonsil, covered with a thin connective tissue capsule, is adjacent directly to the wall of the pharynx, in a special bed. The inner surface of the tonsil, facing the lumen of the pharynx, is pitted with crypts or lacunae of various depths and shapes. The lower pole of the tonsil hangs freely over the root of the tongue.
Upper pole almost closely approaches the angle formed by both arches, leaving space for a triangular depression - fossa supratonsillaris. This supramindal fossa, according to the observations of Orleans, sometimes represents a deep cavity located in the thickness of the soft palate (recessus palatinus) and containing an additional lobe of the tonsil. In some cases, in the thickness of the soft palate there is a tree-like branching canal - sinus tourtual, which essentially represents the deep crypt of the tonsil. These anatomical options are of great importance in clinical practice.
Blood supply to the tonsils deserves special attention. The tonsil artery has a different origin, as can be seen in the attached Bulatnikov diagram.
Lymph circulation of the tonsils. The tonsils represent a peripheral lymphadenoid apparatus, similar to Peyer's patches and solitary intestinal follicles. The tonsils do not have afferent lymphatic pathways. There is no lymph flow from inside the tonsils to its surface. On the contrary, the phenomena of absorption from its pharyngeal surface are observed in the amygdala. The lymph flow from the tonsil goes centripetally and is directed to the corresponding regional lymph nodes.
pharyngeal tonsil, located along, is cut by deep grooves, which extend quite symmetrically on both sides of the median groove. Thus, the entire amygdala is divided into separate lobules. In the posterior part of the median sulcus there is a small depression called the bursa pharyngca.
4th amygdala, located between the root of the tongue and the epiglottis, it represents an accumulation of lymphoid tissue of varying sizes. In pathology it plays the least role. parapharyngeal space, made of loose fiber, it is divided by a special connective tissue plate, together with the muscles attached to the styloid process, into 2 sections. In the anterior section there are: art. maxillar. int., n. auriculo-temporalis, n. lingualis and n. alveolaris inferior, and in the thickness of the parotid gland - the external carotid artery. In the posterior section: internal carotid artery, jugular vein, 9th, 10th, 11th and 12th cephalic nerves and lateral trunk of the sympathetic nerve.
Features of the structure of the palatine tonsils: The functional organization of the palatine tonsils is closest to that of Peyer's patches; in them there is direct close contact of lymphoid elements with the epithelium. The tonsils take part in the implementation of “local” (in the oropharynx) nonspecific immune reactions,
Language
Soft sky. Tongue.
The soft palate and uvula consist of a tendon-muscular base covered with a mucous membrane. In the soft palate and uvula, the oropharyngeal (anterior) and nasopharyngeal (posterior) surfaces are distinguished. In fetuses and newborns, the histological boundary between them runs approximately along the line of inflection of the mucous membrane from the oral surface to the nasal surface on the arches of the soft palate and on the uvula. In adults, this border shifts to the posterior (nasal) surface, so that the entire uvula is covered with the mucous membrane characteristic of the oral cavity.
The mucous membrane of the oral surface of the soft palate and uvula is covered with stratified squamous non-keratinizing epithelium. The lamina propria of the mucous membrane forms high, narrow papillae that protrude deeply into the epithelium. Behind it is a highly developed layer of elastic fibers. The muscular plate of the mucous membrane is absent.
Next comes the submucosa, formed by loose fibrous connective tissue rich in fatty elements, in which the mucous salivary glands are located. The excretory ducts of these glands open on the oral surface of the soft palate and uvula.
In the uvula, clusters of glands are also located inside the muscle layer. The striated muscle tissue that forms the basis of the tongue has a number of features. Its muscle fibers branch and form anastomoses among themselves.
The mucous membrane of the nasal surface of the soft palate is covered, like other airways, with multirow (pseudostratified) ciliated epithelium containing goblet cells. The lamina propria of the mucous membrane here is devoid of papillae and is separated from the epithelium by a well-defined basement membrane. Small mucous-type salivary glands open on the surface of the epithelium. Behind the lamina propria is a layer of elastic fibers. The muscular plate of the mucous membrane and submucosa are absent. At the point of transition of the mucous membrane of the oral surface of the palate into the nasal epithelium, from multilayered squamous epithelium becomes first multilayered prismatic, and then multirow ciliated (i.e. ciliated).
The human tongue, in addition to participating in taste perception, mechanical processing of food and the act of swallowing, is an organ of speech (recte articulation). The basis of the tongue is striated muscle tissue of the somatic type.
The tongue is covered with a mucous membrane. Its relief is different on the lower, lateral and upper surfaces of the tongue. The simplest structure is the mucous membrane on its lower surface. The epithelium here is multilayered squamous, non-keratinizing. The lamina propria of the mucous membrane protrudes into the epithelium, forming short papillae. Following the lamina propria is the submucosa, which is adjacent directly to the muscles. Due to the presence of the submucosa, the mucous membrane of the lower surface of the tongue is easily displaced.
The mucous membrane of the upper and lateral surfaces of the tongue is motionlessly fused with its muscular body and is equipped with special formations - papillae. There is no submucosa. There are 4 types of tongue papillae in the human tongue:
threadlike ( papillae filiformes),
· mushroom-shaped ( papillae fungiformes),
· grooved ( papillae vallatae) And
leaf-shaped ( papillae foliatae).
All papillae of the tongue are derivatives of the mucous membrane and are built according to a general plan. The surface of the papillae is formed by multilayered flat non-keratinizing or partially keratinizing (in filiform papillae) epithelium lying on the basement membrane. The basis of each papilla is an outgrowth (primary papilla) of its own connective tissue layer of the mucous membrane. From the apex of this primary papilla several (5–20) thinner connective tissue secondary papillae extend into the epithelium. In the connective tissue base of the papillae of the tongue there are numerous blood capillaries that are visible through the epithelium (except for filiform ones) and give the papillae a characteristic red color.
Filiform papillae the most numerous, evenly cover the upper surface of the tongue, concentrating especially in the corner formed by the papillae, surrounded by a shaft. In size they are the smallest among the papillae of the tongue. Their length is about 0.3 mm. Along with filiform papillae there are conical (papillae conicae). In a number of diseases, the process of rejection of surface keratinizing epithelial cells can slow down, and epithelial cells, accumulating in large quantities at the tops of the papillae, form powerful horny layers. These masses, covering the surface of the papillae with a whitish film, create a picture of a coated tongue.
Fungiform papillae are few in number and are located on the back of the tongue among the filiform papillae. The largest number of them is concentrated at the tip of the tongue and along its edges. They are larger than filamentous ones - 0.7-1.8 mm in length and about 0.4-1 mm in diameter. The bulk of these papillae have the shape of a mushroom with a narrow base and a wide apex. Among them there are conical and lens-shaped forms.
In the thickness of the epithelium there are taste buds (gemmae gustatoriae), most often located in the area of the “cap” of the fungiform papilla. In sections through this zone, up to 3-4 taste buds are found in each fungiform papilla. Some papillae lack taste buds.
Vital papillae(or papillae surrounded by a shaft) are found on the upper surface of the root of the tongue in numbers from 6 to 12. They are located between the body and the root of the tongue along the border line. They are clearly visible even with the naked eye. Their length is about 1-1.5 mm, diameter 1-3 mm. In contrast to the filiform and mushroom-shaped papillae, which clearly rise above the level of the mucous membrane, the upper surface of these papillae lies almost at the same level with it. They have a narrow base and a wide, flattened free part. Around the papilla there is a narrow, deep gap - the groove (hence the name - grooved papilla). The groove separates the papilla from the ridge, a thickening of the mucous membrane surrounding the papilla. The presence of this detail in the structure of the papilla gave rise to another name - “papilla surrounded by a shaft.” Numerous taste buds are located in the thickness of the epithelium of the lateral surfaces of this papilla and the surrounding ridge. In the connective tissue of the papillae and ridges there are often bundles of smooth muscle cells located longitudinally, obliquely or circularly. The contraction of these bundles brings the papilla closer to the ridge. This promotes the most complete contact of food substances entering the gutter with the taste buds embedded in the epithelium of the papilla and ridge. In the loose fibrous connective tissue of the base of the papilla and between the adjacent bundles of striated fibers there are the terminal sections of the salivary protein glands, the excretory ducts of which open into the gutter. The secretion of these glands washes the groove of the papilla and cleans it of food particles that accumulate in it, exfoliating epithelium and microbes.
Leaf-shaped papillae Languages are well developed only in children. They are presented in two groups, located on the right and left edges of the tongue. Each group includes 4-8 parallel papillae, separated by narrow spaces. The length of one papilla is about 2-5 mm. The epithelium of the lateral surfaces of the papilla contains taste buds. The excretory ducts of the salivary protein glands open into the spaces separating the leaf-shaped papillae. Their end sections are located between the muscles of the tongue. The secretion of these glands flushes the narrow spaces between the papillae. In an adult, the leaf-shaped papillae are reduced, and adipose and lymphoid tissues develop in the places where the protein glands were previously located.
The mucous membrane of the tongue root is characterized by the absence of papillae. However, the surface of the epithelium here is not smooth, but has a number of elevations and depressions. Elevations are formed due to the accumulation of lymph nodes in the lamina propria of the mucous membrane, sometimes reaching 0.5 cm in diameter. Here the mucous membrane forms depressions - crypts, into which the ducts of numerous salivary mucous glands open. The collection of lymphoid tissue accumulations at the root of the tongue is called lingual tonsil.
The muscles of the tongue form the body of this organ. The bundles of striated muscles of the tongue are located in three mutually perpendicular directions: some of them lie vertically, others longitudinally, and others transversely. The muscles of the tongue are divided into right and left halves by a dense connective tissue septum. The loose fibrous connective tissue lying between individual muscle fibers and fascicles contains many fatty lobules. The terminal sections of the salivary glands of the tongue are also located here. At the border between the muscular body and the lamina propria of the mucous membrane of the upper surface of the tongue there is a powerful connective tissue plate consisting of bundles of collagen and elastic fibers intertwined like a lattice. It forms the so-called mesh layer. This is a kind of aponeurosis of the tongue, which is especially strongly developed in the area of the grooved papillae. At the end and at the edges of the tongue, its thickness decreases. Cross-striated muscle fibers, passing through the holes of the reticular layer, are attached to small tendons formed by bundles of collagen fibers lying in the lamina propria of the mucous membrane.
Salivary glands of the tongue (gll. lingualis) are divided into three types: protein, mucous and mixed.
Protein salivary glands are located near the grooved and foliate papillae in the thickness of the tongue. These are simple tubular branched glands. Their excretory ducts open into the ridges of the papillae, surrounded by a shaft, or between the leaf-shaped papillae and are lined with stratified squamous epithelium, sometimes containing cilia. The terminal sections are represented by branched tubes with a narrow lumen. They consist of conical cells that secrete protein secretions, between which intercellular secretory capillaries pass.
The mucous glands are located mainly at the root of the tongue and along its lateral edges. These are single simple alveolar-tubular branched glands. Their ducts are lined with stratified epithelium, sometimes equipped with cilia. At the root of the tongue they open into the crypts of the lingual tonsil. The tubular ends of these glands consist of mucous cells.
Mixed glands are located in its anterior section. Their ducts (about 6 million) open along the folds of the mucous membrane under the tongue. The secretory sections of the mixed glands are located in the thickness of the tongue.
At the border of the oral cavity and pharynx in the mucous membrane there are large accumulations of lymphoid tissue. Together they form a lymphoepithelial pharyngeal ring surrounding the entrance to the respiratory and digestive tracts. The largest clusters of this ring are called tonsils. Based on their location, the palatine tonsils, pharyngeal tonsil, and lingual tonsil are distinguished. In addition to the listed tonsils, in the mucous membrane of the anterior part of the digestive tube there are a number of accumulations of lymphoid tissue, of which the largest are the accumulations in the area of the auditory tubes - tubal tonsils and in the ventricle of the larynx - laryngeal tonsils.
Tonsils perform an important protective function in the body, neutralizing microbes that constantly enter the body from the external environment through the nasal and oral openings. Along with other organs containing lymphoid tissue, they provide the formation of lymphocytes involved in the reactions of humoral and cellular immunity.
Development. The palatine tonsils are formed in the 9th week of embryogenesis in the form of a depression in the pseudostratified ciliated epithelium of the lateral wall of the pharynx, under which lie compactly located mesenchymal cells and numerous blood vessels. At the 11-12th week, the tonsillar sinus is formed, the epithelium of which is reconstructed into a multilayered squamous one, and reticular tissue is differentiated from the mesenchyme; vessels appear, including postcapillary venules with high endothelial cells. The organ is populated with lymphocytes. At week 14, mainly T-lymphocytes (21%) and a few B-lymphocytes (1%) are detected among lymphocytes. At 17-18 weeks, the first lymph nodes appear. By the 19th week, the content of T-lymphocytes increases to 60%, and B-lymphocytes - to 3%. The growth of the epithelium is accompanied by the formation of plugs of keratinizing cells in the epithelial cords.
The pharyngeal tonsil develops in the 4th month of the prenatal period from the epithelium and underlying mesenchyme of the dorsal wall of the pharynx. In the embryo, it is covered with multirow ciliated epithelium. The lingual tonsil develops in the 5th month.
The tonsils reach their maximum development in childhood. The onset of tonsil involution coincides with puberty.
Palatine tonsils in the adult body they are represented by two oval-shaped bodies located on both sides of the pharynx between the palatine arches. Each tonsil consists of several folds of the mucous membrane, in the lamina propria of which there are numerous lymph nodes ( noduli lymphatici). 10–20 crypts extend from the surface of the tonsil deep into the organ ( criptae tonsillares), which branch and form secondary crypts. The mucous membrane is covered with stratified squamous non-keratinizing epithelium. In many places, especially in the crypts, the epithelium is often infiltrated (populated) with lymphocytes and granulocytes. Leukocytes that penetrate into the thickness of the epithelium usually come to its surface in greater or lesser numbers and migrate towards bacteria that enter the oral cavity along with food and air. Microbes in the tonsil are actively phagocytosed by leukocytes and macrophages, and some of the leukocytes die. Under the influence of microbes and various enzymes secreted by leukocytes, the epithelium of the tonsil is often destroyed. However, after some time, due to the proliferation of cells of the epithelial layer, these areas are restored.
The lamina propria of the mucous membrane forms small papillae that protrude into the epithelium. The loose fibrous connective tissue of this layer contains numerous lymph nodes. In the centers of some nodules, lighter areas are clearly visible - germinal centers. Lymphoid nodules of the tonsils are most often separated from each other by thin layers of connective tissue. However, some nodules may merge. The muscular plate of the mucous membrane is not expressed.
The submucosa, located under a cluster of lymphoid nodules, forms a capsule around the tonsil, from which connective tissue septa extend deep into the tonsil. This layer contains the main blood and lymphatic vessels of the tonsil and the branches of the glossopharyngeal nerve that innervate it. The secretory sections of the small salivary glands are also located here. The ducts of these glands open on the surface of the mucous membrane located around the tonsil. Outside the submucosa lie the striated muscles of the pharynx - an analogue of the muscular coat.
Pharyngeal tonsil located in the area of the dorsal wall of the pharynx, lying between the openings of the auditory tubes. Its structure is similar to other tonsils. In the adult body, it is lined with multilayered squamous non-keratinizing epithelium. However, in the crypts of the pharyngeal tonsil and in adults, areas of pseudostratified ciliated epithelium, characteristic of the embryonic period of development, are sometimes found.
In some pathological conditions, the pharyngeal tonsil can be very enlarged (the so-called adenoids).
Lingual tonsil located in the mucous membrane of the root of the tongue. The epithelium covering the surface of the tonsil and lining the crypts is stratified squamous, non-keratinizing. The epithelium and the underlying lamina propria are infiltrated by lymphocytes penetrating here from the lymph nodes. At the bottom of many crypts, the excretory ducts of the salivary glands of the tongue open. Their secretion helps to wash and cleanse the crypts.
81. Large salivary glands, their structure. Teeth and their development.
