Endocrine organs are classified by origin, histogenesis and histological origin into three groups. The branchiogenic group is formed from the pharyngeal pockets - this is the thyroid gland, parathyroid glands. Adrenal group - it belongs to the adrenal glands (medulla and cortex), paraganglia and a group of cerebral appendages - this is the hypothalamus, pituitary gland and pineal gland.
The endocrine system is a functionally regulating system in which there are interorgan connections, and the work of this entire system has a hierarchical relationship with each other.
History of the study of the pituitary gland
The study of the brain and its appendages was done by many scientists in 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 is involved in the formation of cerebrospinal fluid. Another theory was that it absorbs cerebrospinal fluid and then secretes it into the bloodstream.
In 1867 P. I. Peremezhko first mademorphological description of the pituitary gland, highlighting in it the anterior and posterior lobes and the cavity of the cerebral appendages. In a later period in 1984-1986, Dostoevsky and Flesh, studying microscopic fragments of the pituitary gland, found chromophobic and chromophilic cells in its anterior lobe.
Scientists of the 20th century discovered a correlation between the human pituitary gland, whose histology, 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 Turkish saddle of the sphenoid bone and consists of a body and a leg. From above, the Turkish saddle closes the spur of the hard shell of the brain, which serves as a diaphragm for the pituitary gland. The stalk of the pituitary gland passes through the hole in the diaphragm, connecting it with 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 according to gender, disease development, and many other factors.
Pituitary Embryogenesis
Based on the histology of the pituitary gland, it is divided into adenohypophysis and neurohypophysis. The laying of the pituitary gland begins at the fourth week of embryonic development, and two rudiments are used for its formation, which are directed at each other. The anterior lobe of the pituitary gland is formed from the pituitary pocket, which develops from the oral bay of the ectoderm, and the posterior lobe from the brain pocket, formed by the protrusion of the bottomthird cerebral ventricle.
Embryonic histology of the pituitary gland differentiates the formation of basophilic cells already at the 9th week of development, and at the 4th month of acidophilic cells.
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 portion.
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.
Differentiation of secretory granules is represented by their ability to stain when exposed to coloring pigments.
On the periphery of the trabeculae are endocrinocytes that contain secretory substances in their cytoplasm, which are stained, and they are called chromophilic. These cells are divided into two types: acidophilic and basophilic.
Acidophilic adrenocytes stain with eosin. It's an acid dye. Their total number is 30-35%. The cells are round in shape with a nucleus located in the center, with the Golgi complex adjacent to it. The endoplasmic reticulum is well developed and has a granular structure. in acidophilic cells.there is an intensive protein biosynthesis and hormone formation.
In the process of histology of the pituitary gland of the anterior part in acidophilic cells, when they were stained, varieties involved in the production of hormones were identified - somatotropocytes, lactotropocytes.
Acidophilic cells
To acidophilic cells are cells that stain with acidic colors 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 the 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 doubles in size, which is reversible.
Basophilic cells
These cells are relatively larger than acidophilic cells, and their volume occupies only 4-10% in the anterior part of the adenohypophysis. In their structure, these are glycoproteins, which are the matrix forprotein biosynthesis. Cells are stained with a histology of the pituitary gland with a preparation that is determined mainly by aldehyde-fuchsin. Their main cells are thyrotropocytes and gonadotropocytes.
Thyrotropics 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 gland follicles. Their deficiency contributes to an increase in the pituitary gland, as they increase in size.
Gonadotropes make up 10-15% of the volume of the adenohypophysis and their secretory granules are 200 nm in diameter. They can be found in the histology of the pituitary gland in a scattered state in the anterior lobe. It produces follicle-stimulating and luteinizing hormones, and they ensure the full functioning of the gonads of the body of a man and a woman.
Propiomelanocortin
A large secreted glycoprotein measuring 30 kilod altons. It is propioomelanocortin, which, after its splitting, 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 is 15-20% of the anterior pituitary gland, they are basophilic cells.
Chromophobic cells
Melanocyte-stimulating and lipotropic hormones are secreted by chromophobic cells. Chromophobic cells are difficult to stain or do not stain at all. They areare 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 lacking granules are quite specialized cells.
Chromophobic cells also differentiate into small follicle stellate cells with long processes that form a broad network. Their processes pass through endocrinocytes and are located on sinusoidal capillaries. They can form follicular formations and accumulate glycoprotein secretion.
Intermediate and tuberal adenohypophysis
Intermediate cells are weakly basophilic and accumulate glycoprotein secretion. 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 into 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 fusiform or process-shaped. It includes the 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
Good education inanterior pituitary glandular tissue. This formation is formed as a result of hyperplasia - this is the uncontrolled development of a tumor cell.
Histology of pituitary adenoma is used in the study of the causes of the disease and to determine its variety according to the cellular structures of the structure and the anatomical lesion of the growth of the organ. Adenoma can affect the endocrinocytes of basophilic cells, chromophobic 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 pituitary gland of a cat is spherical, and its dimensions are 5x5x2 mm. Histology of the cat's pituitary gland revealed that it consists of an adenohypophysis and a neurohypophysis. The adenohypophysis consists of an anterior and an intermediate lobe, and the neurohypophysis connects to the hypothalamus through a stalk, which is somewhat shorter and thicker in its posterior part.
Staining of microscopic biopsy fragments of the cat's pituitary gland with the drug at multiple magnification histology allows one to see the pink granularity of acidophilic endocrinocytes of the anterior lobe. These are large cells. The posterior lobe is weakly stained, has a rounded shape, and consists of pituicites and nerve fibers.
Studying the histology of the pituitary gland in humans and animals allows you to accumulate scientific knowledge and experience that will help explain the processes occurring in the body.
