Neurohypophysis histology. Histological structure. Histological structure of the adenohypophysis
Endocrine organs are classified according to their origin, histogenesis and histological origin into three groups. The branchiogenic group is formed from the pharyngeal pouches - this is the thyroid group. The adrenal glands belong to the adrenal glands (the medulla and cortex), paraganglia and a group of brain appendages - these are the hypothalamus, pituitary gland and pineal gland.
It is a functionally regulating system in which interorgan connections exist, and the work of this entire system has a hierarchical relationship with each other.
History of the study of the pituitary gland
Many scientists have studied the brain and its appendages different eras. For the first time, Galen and Vesalius thought about the role of the pituitary gland in the body, who believed that it forms mucus in the brain. In later periods, there were conflicting opinions about the role of the pituitary gland in the body, namely, that it participates in the formation of cerebrospinal fluid. Another theory stated that it absorbs cerebrospinal fluid, then secreting it into the blood.
In 1867 P.I. Peremezhko was the first to make a morphological description of the pituitary gland, distinguishing in it the anterior and posterior lobes and the cavity of the cerebral appendages. In more late period in 1984-1986, Dostoevsky and Flesch, studying microscopic fragments of the pituitary gland, discovered chromophobe and chromophilic cells in its anterior lobe.
Scientists of the 20th century discovered a correlation between the human pituitary gland, the histology of which, when studying its secretory secretions, proved this, with the processes occurring in the body.
Anatomical structure and location of the pituitary gland
The pituitary gland is also called the pituitary or pea gland. It is located in the sella turcica sphenoid bone and consists of a body and legs. From above, the sella turcica covers the spur of the dura mater, which serves as a diaphragm for the pituitary gland. The pituitary stalk passes through the hole in the diaphragm, connecting it to the hypothalamus.
It has a reddish-gray color and is covered fibrous capsule, and its weight is 0.5-0.6 g. Its size and weight vary depending on gender, the development of diseases and many other factors.
Embryogenesis of the pituitary gland
Based on the histology of the pituitary gland, it is divided into adenohypophysis and neurohypophysis. The formation of the pituitary gland begins in the fourth week of embryonic development, and for its formation two rudiments are used, which are directed towards each other. The anterior lobe of the pituitary gland is formed from the pituitary recess, which develops from the oral bay of the ectoderm, and the posterior lobe from the medullary recess, formed by the protrusion of the bottom of the third cerebral ventricle.
Embryonic histology of the pituitary gland differentiates the formation of basophilic cells already at the 9th week of development, and acidophilic cells at the 4th month.
Histological structure of the adenohypophysis
Thanks to histology, the structure of the pituitary gland can be represented by the structural parts of the adenohypophysis. It consists of an anterior, intermediate and tuberal part.
The anterior part is formed by trabeculae - these are branched cords consisting of epithelial cells, between which connective tissue fibers and sinusoidal capillaries are located. These capillaries form a dense network around each trabecula, which provides a close connection with the bloodstream. the trabeculae of which it consists are endocrinocytes with secretory granules located in them.
The differentiation of secretory granules is represented by their ability to stain when exposed to coloring pigments.
Along the periphery of the trabeculae there are endocrinocytes containing in their cytoplasm secretory substances that stain and are called chromophilic. These cells are divided into two types: acidophilic and basophilic.
Acidophilic adrenocytes stain with eosin. This is an acidic dye. Their total number is 30-35%. The cells are round in shape with the nucleus located in the center, with the Golgi complex adjacent to it. The endoplasmic reticulum is well developed and has a granular structure. Acidophilic cells undergo intensive protein biosynthesis and hormone formation.
In the process of histology of the anterior pituitary gland, in acidophilic cells, when staining them, varieties involved in the production of hormones were identified - somatotropocytes, lactotropocytes.
Acidophilus cells
Acidophilic cells include cells that are stained with acidic dyes and are smaller in size than basophils. The nucleus in these is located in the center, and the endoplasmic reticulum is granular.
Somatotropocytes make up 50% of all acidophilic cells and their secretory granules, located in the lateral sections of the trabeculae, are spherical in shape and their diameter is 150-600 nm. They produce somatotropin, which is involved in growth processes and is called growth hormone. It also stimulates cell division in the body.
Lactotropocytes have another name - mammotropocytes. They have an oval shape with dimensions of 500-600 by 100-120 nm. They do not have a clear localization in trabeculae and are scattered in all acidophilic cells. Their total number is 20-25%. They produce the hormone prolactin or luteotropic hormone. His functional value consists of the biosynthesis of milk in the mammary glands, the development of the mammary glands and functional state corpus luteum of the ovaries. During pregnancy, these cells increase in size and the pituitary gland becomes twice as large, which is reversible.
Basophil cells
These cells are relatively larger than acidophilus cells, and their volume occupies only 4-10% in the anterior part of the adenohypophysis. By their structure, these are glycoproteins, which are the matrix for protein biosynthesis. Cells in the histology of the pituitary gland are stained with a preparation that is determined mainly by aldehyde-fuchsin. Their main cells are thyrocytes and gonadotropocytes.
Thyrotropes are small secretory granules with a diameter of 50-100 nm, and their volume is only 10%. Their granules produce thyrotropin, which stimulates the functional activity of follicles thyroid gland. Their deficiency contributes to the enlargement of the pituitary gland, as they increase in size.
Gonadotropes make up 10-15% of the volume of the adenohypophysis and their secretory granules have a diameter of 200 nm. In the histology of the pituitary gland, they can be found in a scattered state in the anterior lobe. It produces follicle-stimulating and luteinizing hormones, and they ensure the full functioning of the sex glands of the body of a man and a woman.
Propiomelanocortin
A large secreted glycoprotein measuring 30 kilodaltons. It is propioomelanocortin, which, after its cleavage, forms corticotropic, melanocyte-stimulating and lipotropic hormones.
Corticotropic hormones are produced by the pituitary gland, and their main purpose is to stimulate the activity of the adrenal cortex. Their volume makes up 15-20% of the anterior lobe of the pituitary gland; they belong to basophilic cells.
Chromophobe cells
Melanocyte-stimulating and lipotropic hormones are secreted by chromophobe cells. Chromophobic cells are difficult to stain or cannot be stained at all. They are divided into cells that have already begun to turn into chromophilic cells, but for some reason did not have time to accumulate secretory granules, and cells that intensively secrete these granules. Cells that are depleted or lack granules are quite specialized cells.
Chromophobe cells also differentiate into small-sized cells with long processes that form a broadly woven network, follicle-stellate cells. Their processes pass through endocrinocytes and are located on sinusoidal capillaries. They can form follicular formations and accumulate glycoprotein secretions.
Intermediate and tuberal parts of the adenohypophysis
The cells of the intermediate part are weakly basophilic and accumulate glycoprotein secretions. They have a polygonal shape and their size is 200-300 nm. They synthesize melanotropin and lipotropin, which are involved in pigmentation and fat metabolism in organism.
The tuberal part is formed by epithelial strands that extend to the anterior part. It is adjacent to the pituitary stalk, which is in contact with the medial eminence of the hypothalamus from its lower surface.
Neurohypophysis
The posterior lobe of the pituitary gland consists of which has a fusiform or process form. It includes nerve fibers the anterior zone of the hypothalamus, which are formed by neurosecretory cells of the axons of the paraventricular and supraoptic nuclei. Oxytocin and vasopressin are formed in these nuclei, which enter and accumulate in the pituitary gland.
Pituitary adenoma
Benign formation in the anterior lobe of the pituitary gland This formation is formed as a result of hyperplasia - this is the uncontrolled development of a tumor cell.
The histology of pituitary adenoma is used in studying the causes of the disease and to determine its type based on the anatomical damage to the growth of the organ. Adenoma can affect endocrinocytes of basophilic cells, chromophobe cells and develop on several cellular structures. She may also have different sizes, and this is reflected in its name. For example, microadenoma, prolactinoma and its other varieties.
Animal pituitary gland
The cat's pituitary gland is spherical and measures 5x5x2 mm. Histology of the cat's pituitary gland revealed that it consists of the adenohypophysis and the neurohypophysis. The adenohypophysis consists of the anterior and intermediate lobes, and the neurohypophysis, through a stalk that is somewhat shorter and thicker in its posterior part, connects to the hypothalamus.
Staining microscopic biopsy fragments of the cat pituitary gland with a preparation for histology at multiple magnification allows one to see the pink granularity of acidophilic endocrinocytes of the anterior lobe. These are large cells. The posterior lobe is slightly stained, has a rounded shape and consists of pituicytes and nerve fibers.
Studying the histology of the pituitary gland in humans and animals allows us to accumulate scientific knowledge and experience, which will help explain the processes occurring in the body.
Endocrine organs are classified according to their origin, histogenesis and histological origin into three groups. The branchiogenic group is formed from the pharyngeal pouches - these are the thyroid gland, parathyroid glands. The adrenal gland group - it includes the adrenal glands (medulla and cortex), paraganglia and a group of brain appendages - these are the hypothalamus, pituitary gland and pineal gland.
The endocrine system is a functionally regulating system in which interorgan connections exist, and the work of this entire system has a hierarchical relationship with each other.
History of the study of the pituitary gland
Many scientists in different eras have studied the brain and its appendages. For the first time, Galen and Vesalius thought about the role of the pituitary gland in the body, who believed that it forms mucus in the brain. In later periods, there were conflicting opinions about the role of the pituitary gland in the body, namely, that it participates in the formation of cerebrospinal fluid. Another theory stated that it absorbs cerebrospinal fluid, then secreting it into the blood.
In 1867 P.I. Peremezhko was the first to make a morphological description of the pituitary gland, distinguishing in it the anterior and posterior lobes and the cavity of the cerebral appendages. In a later period in 1984-1986, Dostoevsky and Flesch, studying microscopic fragments of the pituitary gland, discovered chromophobe and chromophilic cells in its anterior lobe. Scientists of the 20th century discovered a correlation between the human pituitary gland, the histology of which, when studying its secretory secretions, proved this, with the processes occurring in the body.
Anatomical structure and location of the pituitary gland
The pituitary gland is also called the pituitary or pea gland. It is located in the sella turcica of the sphenoid bone and consists of a body and a stalk. From above, the sella turcica covers the spur of the dura mater, which serves as a diaphragm for the pituitary gland. The pituitary stalk passes through the hole in the diaphragm, connecting it to the hypothalamus. 
It is reddish-gray in color, covered with a fibrous capsule, and weighs 0.5-0.6 g. Its size and weight vary depending on gender, disease development, and many other factors.
Embryogenesis of the pituitary gland
Based on the histology of the pituitary gland, it is divided into adenohypophysis and neurohypophysis. The formation of the pituitary gland begins in the fourth week of embryonic development, and for its formation two rudiments are used, which are directed towards each other. The anterior lobe of the pituitary gland is formed from the pituitary recess, which develops from the oral bay of the ectoderm, and the posterior lobe from the medullary recess, formed by the protrusion of the bottom of the third cerebral ventricle. 
Embryonic histology of the pituitary gland differentiates the formation of basophilic cells already at the 9th week of development, and acidophilic cells at the 4th month.
Histological structure of the adenohypophysis
Thanks to histology, the structure of the pituitary gland can be represented by the structural parts of the adenohypophysis. It consists of an anterior, intermediate and tuberal part.
The anterior part is formed by trabeculae - these are branched cords consisting of epithelial cells, between which connective tissue fibers and sinusoidal capillaries are located. These capillaries form a dense network around each trabecula, which provides a close connection with the bloodstream. The glandular cells of the trabecula, of which it consists, are endocrinocytes with secretory granules located in them.
The differentiation of secretory granules is represented by their ability to stain when exposed to coloring pigments.
Along the periphery of the trabeculae there are endocrinocytes containing in their cytoplasm secretory substances that stain and are called chromophilic. These cells are divided into two types: acidophilic and basophilic.
Acidophilic adrenocytes stain with eosin. This is an acidic dye. Their total number is 30-35%. The cells are round in shape with the nucleus located in the center, with the Golgi complex adjacent to it. The endoplasmic reticulum is well developed and has a granular structure. Acidophilic cells undergo intensive protein biosynthesis and hormone formation.
In the process of histology of the anterior pituitary gland, in acidophilic cells, when staining them, varieties involved in the production of hormones were identified - somatotropocytes, lactotropocytes.
Acidophilus cells
Acidophilic cells include cells that are stained with acidic dyes and are smaller in size than basophils. The nucleus in these is located in the center, and the endoplasmic reticulum is granular.
Somatotropocytes make up 50% of all acidophilic cells and their secretory granules, located in the lateral sections of the trabeculae, are spherical in shape and their diameter is 150-600 nm. They produce somatotropin, which is involved in growth processes and is called growth hormone. It also stimulates cell division in the body.
Lactotropocytes have another name - mammotropocytes. They have an oval shape with dimensions of 500-600 by 100-120 nm. They do not have a clear localization in trabeculae and are scattered in all acidophilic cells. Their total number is 20-25%. They produce the hormone prolactin or luteotropic hormone. Its functional significance lies in the biosynthesis of milk in the mammary glands, the development of the mammary glands and the functional state of the corpus luteum of the ovaries. During pregnancy, these cells increase in size and the pituitary gland becomes twice as large, which is reversible.
Basophil cells
These cells are relatively larger than acidophilus cells, and their volume occupies only 4-10% in the anterior part of the adenohypophysis. By their structure, these are glycoproteins, which are the matrix for protein biosynthesis. Cells in the histology of the pituitary gland are stained with a preparation that is determined mainly by aldehyde-fuchsin. Their main cells are thyrocytes and gonadotropocytes. 
Thyrotropes are small secretory granules with a diameter of 50-100 nm, and their volume is only 10%. Their granules produce thyrotropin, which stimulates the functional activity of the thyroid follicles. Their deficiency contributes to the enlargement of the pituitary gland, as they increase in size.
Gonadotropes make up 10-15% of the volume of the adenohypophysis and their secretory granules have a diameter of 200 nm. In the histology of the pituitary gland, they can be found in a scattered state in the anterior lobe. It produces follicle-stimulating and luteinizing hormones, and they ensure the full functioning of the sex glands of the body of a man and a woman.
Propiomelanocortin
A large secreted glycoprotein measuring 30 kilodaltons. It is propioomelanocortin, which, after its cleavage, forms corticotropic, melanocyte-stimulating and lipotropic hormones.
Corticotropic hormones are produced by the pituitary gland, and their main purpose is to stimulate the activity of the adrenal cortex. Their volume makes up 15-20% of the anterior lobe of the pituitary gland; they belong to basophilic cells.
Chromophobe cells
Melanocyte-stimulating and lipotropic hormones are secreted by chromophobe cells. Chromophobic cells are difficult to stain or cannot be stained at all. They are divided into cells that have already begun to turn into chromophilic cells, but for some reason did not have time to accumulate secretory granules, and cells that intensively secrete these granules. Cells that are depleted or lack granules are quite specialized cells.
Chromophobe cells also differentiate into small-sized cells with long processes that form a broadly woven network, follicle-stellate cells. Their processes pass through endocrinocytes and are located on sinusoidal capillaries. They can form follicular formations and accumulate glycoprotein secretions.
Intermediate and tuberal parts of the adenohypophysis
The cells of the intermediate part are weakly basophilic and accumulate glycoprotein secretions. They have a polygonal shape and their size is 200-300 nm. They synthesize melanotropin and lipotropin, which are involved in pigment and fat metabolism in the body.
The tuberal part is formed by epithelial strands that extend to the anterior part. It is adjacent to the pituitary stalk, which is in contact with the medial eminence of the hypothalamus from its lower surface.
Neurohypophysis
The posterior lobe of the pituitary gland consists of neuroglia, the cells of which are spindle-shaped or process-shaped. It includes nerve fibers of the anterior zone of the hypothalamus, which are formed by neurosecretory cells of the axons of the paraventricular and supraoptic nuclei. Oxytocin and vasopressin are formed in these nuclei, which enter and accumulate in the pituitary gland.
Pituitary adenoma
Benign formation in the anterior lobe of the pituitary gland of glandular tissue. This formation is formed as a result of hyperplasia - this is the uncontrolled development of a tumor cell. 
The histology of pituitary adenoma is used to study the causes of the disease and to determine its type based on the cellular structures of the structure and the anatomical damage to the growth of the organ. Adenoma can affect endocrinocytes of basophilic cells, chromophobe cells and develop on several cellular structures. It can also have different sizes, and this is reflected in its name. For example, microadenoma, prolactinoma and its other varieties.
Animal pituitary gland
The cat's pituitary gland is spherical and measures 5x5x2 mm. Histology of the cat's pituitary gland revealed that it consists of the adenohypophysis and the neurohypophysis. The adenohypophysis consists of the anterior and intermediate lobes, and the neurohypophysis, through a stalk that is somewhat shorter and thicker in its posterior part, connects to the hypothalamus. 
Staining microscopic biopsy fragments of the cat pituitary gland with a preparation for histology at multiple magnification allows one to see the pink granularity of acidophilic endocrinocytes of the anterior lobe. These are large cells. The posterior lobe is slightly stained, has a rounded shape and consists of pituicytes and nerve fibers.
Studying the histology of the pituitary gland in humans and animals allows us to accumulate scientific knowledge and experience, which will help explain the processes occurring in the body.
117. Pituitary gland. Development, structure, blood supply and functions of individual lobes.
Development. The pituitary gland develops from: 1) the epithelium of the roof oral cavity, which itself develops from the ectoderm, and 2) the distal end of the infundibulum of the floor of the 3rd ventricle. The adenohypophysis develops from the epithelium of the oral cavity (ectoderm) at the 4-5th week of embryogenesis. As a result of protrusion of the epithelium of the oral cavity towards the bottom of the 3rd ventricle, a pituitary pouch is formed. A funnel grows towards the pituitary recess from the bottom of the 3rd ventricle. When the distal end of the infundibulum is aligned with the pituitary recess, the anterior wall of this recess thickens and becomes the anterior lobe, the posterior wall becomes the intermediate part, and the distal end of the infundibulum becomes the posterior lobe of the pituitary gland.
Structure. The pituitary gland consists of the adenohypophysis (anterior lobe, intermediate lobe, tuberal part) and the neurohypophysis (posterior lobe).
Anterior lobe hidden by a connective capsule, from which extend layers of connective tissue that make up the stroma of the organ. The parenchyma of the organ is epithelial cells called adenocytes, which are arranged in cords.
Cells of the anterior lobe:
chromophilic (contain granules that are colored with dyes)
basophilic (10%)
Gonadotropic
Thyrotropic
acidophilic
Somatotropic
Mammatropic
chromophobic (does not contain granules, therefore they are not colored) (60%)
undifferentiated
differentiating
chromophilic mature
stellate-follicular
corticotropic
Gonadotropic endocrinocytes- the largest cells have a round, sometimes angular shape, an oval or round nucleus, shifted to the periphery, since in the center of the cell there is a macula (spot), in which the Golgi complex and the cell center are located. In the cytoplasm, granular EPS, mitochondria and the Golgi complex are well developed, as well as basophilic granules with a diameter of 200-300 nm, consisting of glycoproteins and stained with aldehyde fuchsin. It is believed that there are 2 types of gonadotropic endocrinocytes, some of which secrete follitropin, others - lutropin.
Folliculotropic hormone (follitropin) in the male body it acts on the initial stage of spermatogenesis, in the female body - on the growth of follicles and the release of estrogens in the gonads.
Lutropin stimulates the secretion of testosterone in the male gonads and the development and function of the corpus luteum in the female gonads.
Castration cells appear in the anterior lobe in cases where the gonads produce insufficient amounts of sex hormones.
Thyrotropic endocrinocytes have an oval or elongated shape, an oval core. Their cytoplasm has a well-developed Golgi complex, granular ER and mitochondria, and contains basophilic granules 80-150 nm in size, stained with aldehyde fuchsin. Thyrotropic endocrinocytes, under the influence of thyroliberin, produce thyrotropic hormone, which stimulates the release of thyroxine by the thyroid gland.
Thyroidectomy cells appear in the pituitary gland when the function of the thyroid gland decreases. In these cells, granular EPS hypertrophies, its cisterns expand, and the secretion of thyroid-stimulating hormone increases. As a result of the expansion of the tubules and EPS cisterns, the cytoplasm of the cells acquires a cellular appearance.
Corticotropic endocrinocytes They are neither acidophilic nor basophilic; they have an irregular shape, a lobed nucleus, and their cytoplasm contains small granules. Under the influence of corticoliberins produced in the nuclei of the mediobasal hypothalamus, these cells secrete corticotropic or adrenocorticotropic hormone (ACTH), which stimulates the function of the adrenal cortex.
Acidophilic endocrinocytes make up 35-40% and are divided into 2 varieties, which are usually round in shape, with an oval or round core located in the center. The cells have a well-developed synthetic apparatus, i.e. the Golgi complex, granular ER, mitochondria; the cytoplasm contains acidophilic granules.
Somatotropic endocrinocytes contain oval or round granules with a diameter of 400-500 nm, produce somatotropic hormone, which stimulates body growth in childhood and adolescence. With hyperfunction of somatotropic cells after completion of growth, acromegaly develops - a disease characterized by the appearance of a hump, an increase in the size of the tongue, lower jaw, hands and feet.
Mammotropic endocrinocytes contain elongated granules reaching sizes of 500-600 nm in parturient and pregnant women. In non-nursing mothers, the granules are reduced to 200 nm. These adenocytes secrete mammotropic hormone, or prolactin. Functions: 1) stimulates milk synthesis in the mammary glands; 2) stimulates the development of the corpus luteum in the ovaries and the secretion of progesterone.
Chromophobic (main) endocrinocytes make up about 60%, are smaller in size, do not contain stainable granules, so their cytoplasm is not stained. The composition of chromophobe adenocytes includes 4 groups:
1) undifferentiated (perform a regenerative function);
2) differentiating, i.e. they began to differentiate, but differentiation did not end, only single granules appeared in the cytoplasm, therefore the cytoplasm is weakly stained;
3) chromophilic mature cells that have just released their secretory granules and therefore have decreased in size and the cytoplasm has lost the ability to stain;
4) stellate-follicular cells, characterized by long processes spreading between endocrinocytes.
A group of such cells, with their apical surfaces facing each other, secretes a secretion, resulting in the formation of pseudofollicles filled with colloid.
Intermediate part (lobe) of the adenohypophysis It is represented by epithelium located in several layers, localized between the anterior and posterior lobes of the pituitary gland. In the intermediate part there are pseudofollicles containing a colloid-like mass. Functions: 1) secretion of melanotropic (melanocyte-stimulating) hormone, which regulates the metabolism of melanin pigment; 2) lipotropic hormone that regulates lipid metabolism.
Tuberal part of the adenohypophysis(pars tuberalis) is located next to the pituitary stalk, consists of intertwined strands of cubic-shaped epithelial cells, and is richly vascularized. Function little studied.
Posterior pituitary gland (neurohypophysis) represented mainly by ependymal glia. Neuroglial cells are called pituicytes. The neurohypophysis does not produce hormones (it is a neurohemal organ). The posterior lobe receives axons from the neurosecretory cells of the supraoptic and paraventricular nuclei. Vasopressin and oxytocin are transported along these axons to the posterior lobe and accumulate on the axon terminals near the blood vessels (it is a depot reservoir for these hormones). These savings are called storage bodies, or Herring's bodies. As needed, hormones flow from these bodies into the blood vessels.
Blood supply. Called the hypothalamic-adenopituitary or pormal system. The afferent pituitary arteries enter the medial eminence of the hypothalamus, where they branch into a network of capillaries (primary capillary plexus). These capillaries form loops and glomeruli with which the axon terminals of the neurosecretory cells of the adenopituitary zone of the hypothalamus contact. The capillaries of the primary plexus are collected in portal veins, running along the pituitary stalk into the anterior lobe, where they break up into sinusoidal capillaries (secondary capillary network), branching between the trabeculae of the gland parenchyma. Finally, the sinusoids of the secondary capillary network are collected in the efferent veins, through which blood, enriched with the hormones of the anterior lobe, enters the general circulation.
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Pituitary(pituitary gland) together with the hypothalamus makes up the hypothalamic-pituitary neurosecretory system. It is a brain appendage. The pituitary gland is divided into adenohypophysis (anterior lobe, intermediate and tuberal parts) and neurohypophysis (posterior lobe, infundibulum).
Development. The adenohypophysis develops from the epithelium of the roof of the oral cavity. At the 4th week of embryogenesis, an epithelial protrusion is formed in the form of a pituitary pouch (Rathke's pouch), from which the gland with external type secretion. Then proximal part The pouch is reduced, and the adenomere becomes a separate endocrine gland. The neurohypophysis is formed from the material of the infundibular part of the bottom of the third ventricle of the brain and is of neural origin. These two parts, different in origin, come into contact to form the pituitary gland.
Structure. The adenohypophysis consists of epithelial strands - trabeculae. Sinusoidal capillaries pass between them. The cells are represented by chromophilic and chromophobic endocrinocytes. Among chromophilic endocrinocytes, acidophilic and basophilic endocrinocytes are distinguished.
Acidophilic endocrinocytes- these are medium-sized cells, round or oval shape, with a well-developed granular endoplasmic reticulum. The nuclei are located in the center of the cells. They contain large dense granules that are stained with acidic dyes. These cells lie on the periphery of the trabeculae and make up 30-35% of the total number of adenocytes in the anterior lobe of the pituitary gland. There are two types of acidophilic endocrinocytes: somatotropocytes, which produce growth hormone (somatotropin), and lactotropocytes, or mammotropocytes, which produce lactotropic hormone (prolactin). Somatotropin stimulates the growth processes of all tissues and organs.
With hyperfunction of somatotropocytes Acromegaly and gigantism may develop, and in conditions of hypofunction, a slowdown in body growth, which leads to pituitary dwarfism. Lactotropic hormone stimulates the secretion of milk in the mammary glands and progesterone in corpus luteum ovary.
Basophilic endocrinocytes- these are large cells, in the cytoplasm of which there are granules that are stained with basic dyes (aniline blue). They make up 4-10% of total number cells in the anterior lobe of the pituitary gland. The granules contain glycoproteins. Basophilic endocrinocytes are divided into thyrotropocytes and gonadotropocytes.
Thyrotropocytes- these are cells with a large number dense small granules, stained with aldehyde fuchsin. They produce thyroid-stimulating hormone. When there is a lack of thyroid hormones in the body, thyrocytes are transformed into thyroidectomy cells with a large number of vacuoles. At the same time, the production of thyrotropin increases.
Gonadotropocytes- rounded cells in which the nucleus is mixed towards the periphery. In the cytoplasm there is a macula - a bright spot where the Golgi complex is located. Small secretory granules contain gonadotropic hormones. When there is a lack of sex hormones in the body, castration cells appear in the adenohypophysis, which are characterized by a ring-shaped shape due to the presence of a large vacuole in the cytoplasm. This transformation of the gonadotropic cell is associated with its hyperfunction. There are two groups of gonadotrophocytes that produce either follicle-stimulating or luteinizing hormones.
Corticotropocytes- these are cells of irregular, sometimes process-like shape. They are scattered throughout the anterior lobe of the pituitary gland. In their cytoplasm, secretory granules are detected in the form of a vesicle with a dense core, surrounded by a membrane. There is a light rim between the membrane and the core. Corticotropocytes produce ACTH (adrenocorticotropic hormone), or corticotropin, which activates the cells of the zona fasciculata and zona reticularis of the adrenal cortex.
Chromophobic endocrinocytes make up 50-60% of the total number of cells of the adenohypophysis. They are located in the middle of the trabeculae, are small in size, do not contain granules, and their cytoplasm is weakly stained. This is a collective group of cells, among which there are young chromophilic cells that have not yet accumulated secretory granules, mature chromophilic cells that have already secreted secretory granules, and reserve cambial cells.
Thus, in adenohypophysis a system of interacting cellular differons is discovered, forming the leading epithelial tissue this part of the gland.
Middle (intermediate) lobe of the pituitary gland in humans it is poorly developed, accounting for 2% of the total volume of the pituitary gland. The epithelium in this lobe is homogeneous, the cells are rich in mucoid. In some places there is a colloid. In the intermediate lobe, endocrinocytes produce melanocyte-stimulating hormone and lipotropic hormone. The first adapts the retina to vision at dusk, and also activates the adrenal cortex. Lipotropic hormone stimulates fat metabolism.
Effect of hypothalamic neuropeptides on endocrinocytes is carried out using the hypothalamic-adenopituitary circulatory system (portal).
Into the primary capillary network The median eminence secretes hypothalamic neuropeptides, which then enter the adenohypophysis and its secondary capillary network through the portal vein. Sinusoidal capillaries the latter are located between the epithelial strands of endocrinocytes. This is how neuropeptides from the hypothalamus act on target cells of the adenohypophysis.
Neurohypophysis has a neuroglial nature, is not a hormone-producing gland, but plays the role of a neurohemal formation in which hormones of some neurosecretory nuclei of the anterior hypothalamus accumulate. In the posterior lobe of the pituitary gland there are numerous nerve fibers of the hypothalamic pituitary tract. These are nerve processes of neurosecretory cells of the supraoptic and paraventricular nuclei of the hypothalamus. Neurones of these nuclei are capable of neurosecretion. The neurosecretion (transducer) is transported along the nerve processes to the posterior lobe of the pituitary gland, where it is detected in the form of Herring bodies. The axons of neurosecretory cells end in the neurohypophysis with neurovascular synapses, through which neurosecretion enters the blood.
Neurosecret contains two hormones: antidiuretic (ADH), or vasopressin (it acts on nephrons, regulating the reabsorption of water, and also constricts blood vessels, increasing blood pressure); oxytocin, which stimulates contraction of the smooth muscles of the uterus. Medicine, obtained from the posterior lobe of the pituitary gland, is called pituitrin and is used to treat diabetes insipidus. The neurohypophysis contains neuroglial cells called pituicytes.
Reactivity of the hypothalamic-pituitary system. Combat injuries and accompanying stress lead to complex disturbances in the neuroendocrine regulation of homeostasis. At the same time, neurosecretory cells of the hypothalamus increase the production of neurohormones. In the adenohypophysis, the number of chromophobe endocrinocytes decreases, which weakens the reparative processes in this organ. The number of basophilic endocrinocytes increases, and large vacuoles appear in acidophilic endocrinocytes, indicating their intense functioning. With long-term radiation damage in the endocrine glands, destructive changes occur in secretory cells and inhibition of their function.
Hypothalamus
The hypothalamus is the highest nerve control center endocrine functions. This site diencephalon is also the center of the sympathetic and parasympathetic divisions of the autonomic nervous system. It controls and integrates all visceral functions of the body and combines endocrine regulatory mechanisms with nervous ones. Nerve cells hypothalamus, which synthesize and release hormones into the blood, are called neurosecretory cells. These cells receive afferent nerve impulses from other parts of the nervous system, and their axons end on blood vessels, forming axo-vasal synapses through which hormones are released.
Neurosecretory cells are characterized by the presence of neurosecretory granules that are transported along the axon. In some places, neurosecret accumulates in large quantities, stretching the axon. The largest of these areas are clearly visible under light microscopy and are called Herring bodies. Most of the neurosecret is concentrated in them; only about 30% of it is in the area of the terminals.
The hypothalamus is conventionally divided into anterior, middle and posterior sections.
IN anterior hypothalamus There are paired supraoptic and paraventricular nuclei formed by large cholinergic neurosecretory cells. In the neurons of these nuclei, protein neurohormones are produced - vasopressin, or antidiuretic hormone, and oxytocin. In humans, the production of antidiuretic hormone occurs predominantly in the supraoptic nucleus, while the production of oxytocin predominates in the paraventricular nuclei.
Vasopressin causes an increase in the tone of smooth muscle cells of arterioles, leading to an increase in blood pressure. The second name for vasopressin is antidiuretic hormone (ADH). By acting on the kidneys, it ensures the reabsorption of fluid filtered into primary urine from the blood.
Oxytocin causes contractions of the muscular lining of the uterus during labor, as well as contraction of myoepithelial cells in the mammary gland.
IN middle hypothalamus neurosecretory nuclei are located, containing small adrenergic neurons that produce adenohypophysiotropic neurohormones - liberins and statins. With the help of these oligopeptide hormones, the hypothalamus controls the hormone-producing activity of the adenohypophysis. Liberins stimulate the release and production of hormones by the anterior and middle lobes of the pituitary gland. Statins inhibit the functions of the adenohypophysis.
The neurosecretory activity of the hypothalamus is influenced by the higher parts of the brain, especially the limbic system, amygdala, hippocampus and pineal gland. The neurosecretory functions of the hypothalamus are also strongly influenced by some hormones, especially endorphins and enkephalins.
Pituitary
The pituitary gland, the lower appendage of the brain, is also a central organ endocrine system. It regulates the activity of a number of endocrine glands and serves as a site for the release of hypothalamic hormones (vasopressin and oxytocin).
The pituitary gland consists of two parts, different in origin, structure and function: the adenohypophysis and the neurohypophysis.
IN adenohypophysis distinguish between the anterior lobe, the intermediate lobe and the tuberal part. The adenohypophysis develops from the pituitary recess lining the upper part of the oral cavity. Hormone-producing cells of the adenohypophysis are epithelial and have ectodermal origin (from the epithelium of the oral bay).
IN neurohypophysis distinguish between the posterior lobe, stalk and infundibulum. The neurohypophysis is formed as a protrusion of the diencephalon, i.e. has a neuroectodermal origin.
The pituitary gland is covered with a capsule made of dense fibrous fabric. Its stroma is represented by very thin layers of connective tissue associated with a network of reticular fibers, which in the adenohypophysis surrounds strands of epithelial cells and small vessels.
The anterior lobe of the pituitary gland is formed by branched epithelial strands - trabeculae, forming a relatively dense network. The spaces between the trabeculae are filled with loose fibrous connective tissue and sinusoidal capillaries entwining the trabeculae.
Endocrinocytes, located along the periphery of trabeculae, contain secretory granules in their cytoplasm that intensively perceive dyes. These are chromophilic endocrinocytes. Other cells occupying the middle of the trabecula have unclear boundaries, and their cytoplasm is weakly stained - these are chromophobe endocrinocytes.
Chromophilic endocrinocytes are divided into acidophilic and basophilic according to the staining of their secretory granules.
Acidophilic endocrinocytes are represented by two types of cells.
The first type of acidophilic cells is somatotropes- produce somatotropic hormone (GH), or growth hormone; the action of this hormone is mediated by special proteins - somatomedins.
The second type of acidophilic cells is lactotropes- produce lactotropic hormone (LTH), or prolactin, which stimulates the development of mammary glands and lactation.
Basophilic cells of the adenohypophysis are represented by three types of cells (gonadotropes, thyrotropes and corticotropes).
The first type of basophilic cells is gonadotropes- produce two gonadotropic hormones - follicle-stimulating and luteinizing:
- follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles and spermatogenesis;
- Luteinizing hormone (LH) promotes the secretion of female and male sex hormones and the formation of the corpus luteum.
The second type of basophilic cells is thyrotropes- produce thyroid-stimulating hormone (TSH), which stimulates the activity of the thyroid gland.
The third type of basophilic cells is corticotropes- produce adrenocorticotropic hormone (ACTH), which stimulates the activity of the adrenal cortex.
Most cells of the adenohypophysis are chromophobic. Unlike the described chromophilic cells, chromophobe cells poorly perceive dyes and do not contain distinct secretory granules.
Chromophobic cells are heterogeneous, they include:
- chromophilic cells - after excretion of secretion granules;
- poorly differentiated cambial elements;
- so-called follicular stellate cells.
The middle (intermediate) lobe of the pituitary gland is represented by a narrow strip of epithelium. Endocrinocytes of the intermediate lobe are capable of producing melanocyte-stimulating hormone (MSH), and lipotropic hormone (LPG) that enhances lipid metabolism.
Features of the hypothalamic-adenopituitary blood supply
The hypothalamic-adenopituitary blood supply system is called portal, or portal. The afferent pituitary arteries enter the medial eminence of the hypothalamus, where they branch into a network of capillaries - the primary capillary plexus portal system. These capillaries form loops and glomeruli with which the neurosecretory cells of the adenohypophysiotropic zone of the hypothalamus contact, releasing liberins and statins into the blood. The capillaries of the primary plexus are collected in portal veins, running along the pituitary stalk into the anterior lobe of the pituitary gland, where they break up into sinusoidal capillaries - a secondary capillary network, branching between the trabeculae of the gland parenchyma. Finally, the sinusoids of the secondary capillary network They are collected in the efferent veins, through which blood, enriched with hormones of the anterior lobe, enters the general circulation.
The posterior lobe of the pituitary gland, or neurohypophysis, contains:
- processes and terminals of neurosecretory cells of the supraoptic and paraventricular nuclei of the hypothalamus, through which the hormones vasopressin and oxytocin are transported and released into the blood; expanded areas along the processes and terminals are called storage Herring bodies;
- numerous fenestrated capillaries;
- pituicytes - branched glial cells that perform support and trophic functions; their numerous thin processes cover the axons and terminals of neurosecretory cells, as well as the capillaries of the neurohypophysis.
Age-related changes in the pituitary gland. In the postnatal period, predominantly acidophilic cells are activated (obviously due to the provision of increased production of somatotropin, which stimulates fast growth body), and thyrotropocytes predominate among basophils. IN puberty when it comes puberty, the number of basophilic gonadotropes increases.
The adenohypophysis has limited regenerative capacity, mainly due to the specialization of chromophobe cells. The posterior lobe of the pituitary gland, formed by neuroglia, regenerates better.
Pineal gland
The pineal gland is the upper appendage of the brain, or the pineal body (corpus pineale), involved in the regulation of cyclic processes in the body.
The pineal gland develops as a protrusion of the roof III ventricle diencephalon. The pineal gland reaches its maximum development in children under 7 years of age.
The structure of the pineal gland
Outside, the epiphysis is surrounded by a thin connective tissue capsule, from which branching septa extend into the gland, forming its stroma and dividing its parenchyma into lobules. In adults, dense layered formations are detected in the stroma - epiphyseal nodules, or brain sand.
In the parenchyma there are two types of cells - secreting pinealocytes and supporting glial, or interstitial cells. Pinealocytes are located in the central part of the lobules. They are somewhat larger than supporting neuroglial cells. Long processes extend from the body of the pinealocyte, branching like dendrites, which intertwine with the processes of glial cells. The processes of pinealocytes are directed to the fenestrated capillaries and come into contact with them. Among pinealocytes, light and dark cells are distinguished.
Glial cells predominate at the periphery of the lobules. Their processes are directed to the interlobular connective tissue septa, forming a kind of marginal border of the lobule. These cells perform mainly a supporting function.
Pineal gland hormones:
Melatonin- photoperiodic hormone, - is released mainly at night, because its secretion is inhibited by impulses coming from the retina. Melatonin is synthesized by pinealocytes from serotonin; it inhibits the secretion of GnRH by the hypothalamus and gonadotropins of the anterior pituitary gland. In case of dysfunction of the pineal gland in childhood Precocious puberty is observed.
In addition to melatonin, the inhibitory effect on sexual functions is also determined by other pineal gland hormones - arginine-vasotocin, antigonadotropin.
Adrenoglomerulotropin pineal gland stimulates the formation of aldosterone in the adrenal glands.
Pinealocytes produce several dozen regulatory peptides. Of these, the most important are arginine-vasotocin, thyroliberin, luliberin and even thyrotropin.
The formation of oligopeptide hormones together with neuroamines (serotonin and melatonin) demonstrates that pineal cells of the pineal gland belong to the APUD system.
In humans, the pineal gland reaches its maximum development by 5-6 years of life, after which, despite its continued functioning, its age-related involution begins. A certain number of pinealocytes undergo atrophy, and the stroma grows, and in it the deposition of nodules increases - phosphate and carbonate salts in the form of layered balls - the so-called. brain sand.
(see also from general histology)
Some terms from practical medicine:
- diabetes-- general name for a group of diseases characterized by excessive excretion of urine from the body;
- diabetes insipidus, diabetes insipidus, diabetes insipidus - diabetes caused by the absence or decreased secretion of antidiuretic hormone or the insensitivity of the renal tubular epithelium to it;
- dwarfism, nanism -- clinical syndrome characterized by extremely short stature (compared to the gender and age norm);
- pituitary dwarfism, pituitary dwarfism - dwarfism, combined with a proportional physique, caused by insufficiency of the anterior lobe of the pituitary gland; combined with developmental disorders of other endocrine glands and genital organs;
- pinealoma-- a tumor arising from the parenchymal cells of the pineal body (pinealocytes);
- Pellizzi syndrome, epiphyseal virilism - the appearance of male secondary sexual characteristics in girls, caused by dysfunction of the pineal gland due to its tumors - teratoma, chorionepithelioma, pinealoma;