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Scientific electronic library. Adrenal glands: their structure, topography, blood supply, innervation, hormones, hypo-, hyperfunction Outflow of blood from the left adrenal gland

The adrenal glands are paired endocrine glands that are located near the upper pole of the right and left kidneys in the retroperitoneal space. Typically, the right adrenal gland is triangular in shape, while the left is crescent shaped. The main function of the adrenal glands is the regulation of metabolism and adaptation of the human body to stressful situations.

The adrenal glands are divided into two main anatomical zones - the adrenal cortex and the adrenal medulla.

The adrenal cortex is responsible for the production of hormones that belong to the group of corticosteroids.

In the adrenal cortex there are three zones: the outer zone - the glomerular zone, which is located immediately under the adrenal capsule, then the zona fasciculata of the adrenal gland and the zona reticularis of the adrenal gland, which surrounds the medulla.

Hormones of the zona glomerulosa of the adrenal cortex - meneralocorticoids

The main representative is aldosterone. The main function of the hormone aldosterone is the secretion of potassium ions into the urine and the reabsorption of sodium ions into the blood in the kidneys.

Hormones of the zona fasciculata of the adrenal cortex - glucocorticoids

The main representative is cortisol. Cortisol affects almost all metabolic processes in the human body - the metabolism of fat, carbohydrates, and proteins. Affects the cardiovascular system, kidneys, and the activity of the central nervous system.

Hormones of the zona reticularis of the adrenal cortex - sex hormones, androgens

The main representative is dehydroepiandrosterone (DHEAS), which stimulates protein synthesis, increases muscle mass and muscle contractility.

Adrenal medulla

The medulla is located in the center of the adrenal gland and makes up no more than 10% of its mass. It is important to note that the adrenal medulla and the adrenal cortex are completely different structures in origin. The adrenal cortex is of ectodermal origin. The adrenal medulla is derived from the primary neural crest.

Adrenal medulla cells synthesize catecholamines - norepinephrine and adrenaline.

The main function of adrenal medulla hormones is to increase blood pressure, enhance heart function, expand the lumen of the bronchi, and influence metabolic processes in the body.

Blood supply to the adrenal glands

Good blood supply to the adrenal glands is important for optimal functioning of the entire human body. Each adrenal gland receives its blood supply from the superior, middle and inferior adrenal arteries, which in turn arise from the inferior phrenic artery, abdominal aorta and renal artery. The adrenal venous system forms a central vein, which flows into the inferior vena cava from the right adrenal gland, from the left adrenal gland into the left renal vein.

Innervation of the adrenal glands

The adrenal glands have a large number of nerve fibers. Innervation of the adrenal glands comes from the abdominal and thoracic nerve plexus. Nerve endings largely innervate the adrenal medulla, as well as partially the cortical layer.

The adrenal glands are paired endocrine organs. The weight and size of one gland are individual. The weight of each adrenal gland ranges from 7 to 20 g in an adult, and in a newborn it is 4-6 g.

In fact, these are 2 different glands: the cortex (it accounts for approximately 80% of the organ’s mass) and the medulla. The adrenal cortex produces corticosteroids (glucocorticoids, mineralocorticoids, sex hormones), and the chromaffin tissue of the brain produces catecholamines (norepinephrine, adrenaline and dopamine).

The structure of the adrenal glands and their functions

The adrenal glands, like other organs of the endocrine system, perform a single role in the body - they synthesize hormones. The latter have a targeted, specific effect on the functions of various human organs.

The adrenal glands are divided into two parts - the cortex (bark) and the medulla. On the outside, the gland is surrounded by a capsule of connective tissue, consisting of two layers: outer (dense) and inner (loose). From the latter, in some places connective tissue septa penetrate into the thickness of the organ.

In addition to specialized endocrine cells, loose fibrous connective tissue is found in the cortex of the gland. The latter contains a huge number of capillaries with fenestrated endothelium. The endocrine part of the gland's cortex is a collection of epithelial strands. They have different orientations at different distances from the capsule. This fact, as well as the production of certain hormones, allows us to distinguish 3 zones in the cortex:

Cortical zones	Characteristic
Glomerular	This zone occupies 15% of the thickness of the cortex. Rows of endocrine cells are tucked under the capsule and, when cut, look like glomeruli. The production of mineralocorticoids (mainly aldosterone) occurs in this zone. The latter affect water and electrolyte balance. Stimulates the formation of aldosterone - angiotensin II and ACTH (to a slight extent)
Beam	Makes up about 75% of the thickness of the cortex. The rows of endocrine cells and the blood capillaries located between them are located parallel to each other (in the form of bundles). Glucocorticosteroids (GCS - mainly cortisol and cortisone), as well as steroid hormones such as androgens (in small quantities) are formed here. Their production is regulated by the adenohypophysis hormone - ACTH. GCS affect all types of metabolism and the immune system. And sex hormones affect the functioning of the reproductive system
Mesh	Occupies 10% of the thickness of the cortex. In the deepest parts of the cortex, rows of endocrine cells intertwine, forming a kind of network. Glucocorticosteroids (in small quantities) and androgens (androstenedione and dehydroepiandrosterone), as well as progesterone and its analogs are formed here. Their products are similarly regulated by ACTH

Testosterone is subsequently formed from dihydroepiandrosterone in the gonads. In men, the biochemical process in the testicles stops at this stage. In women, with the help of the aromatase enzyme, located in the ovaries, mammary glands, and adipose tissue, the substance is converted into estrogens. But they still produce a small amount of testosterone.

The endocrine function of the medulla of the glands is performed by chromaffin cells of neuronal origin (analogues of neurons). When the sympathetic nervous system is activated, the adrenal glands release catecholamines (norepinephrine and adrenaline) into the blood. These hormones have a wide range of effects (they affect fat and carbohydrate metabolism, the cardiovascular system - heart rate, blood pressure).

The structure of the adrenal glands and the hormones they secrete.

The pathway for the release of hormones by endocrine cells.

Regeneration and age-related changes

The cells of the cortex and medulla of the gland are able to maintain their numbers both through their division and through the cambial reserve.

Directly under the organ capsule are epithelial cambial cells, which constantly differentiate into endocrine cells of the cortex. ACTH stimulates the division of the cambial reserve.

If excess ACTH persists for a long time, a disease such as adrenal hyperplasia develops. This pathology is characterized by symptoms of excessive secretion of cortical hormones, which is manifested by disturbances of all types of metabolism (water retention in the body, increased sodium concentration in the blood, obesity, etc.) and most systems.

Some of the neural crest cells that migrate into the medulla are retained as a cambial reserve. These poorly differentiated cells are the source of the formation of tumors (pheochromocytomas), which produce excessive amounts of catecholamines.

Most pheochromocytomas are solitary lesions. Their location varies - 10–20% are found outside the paired glands, 1–3% in the neck or chest. In 20% of cases the tumors are multiple, and in 10% they are malignant. The only treatment for pheochromocytomas is removal of the endocrine neoplasm.

In humans, the adrenal cortex reaches full development at the age of 20-25 years. Then the ratio of its zones is 1:9:3. After 60 years, the width of this part of the gland begins to decrease. Only the brain matter does not undergo significant changes with age.

Anatomy

These paired glands are located retroperitoneally, at the upper poles of the kidney at the level of the 10th and 12th thoracic vertebrae, occasionally reaching the 1st lumbar. The adrenal glands are enclosed in fascial beds, the fiber of which is isolated from the perinephric fiber.

Each has:

anterior, posterior and renal surfaces;
top and inner edges.

Basic information about the topographic anatomy of the adrenal glands:

Blood supply and innervation

The adrenal glands are supplied with blood through 3 arteries:

the superior adrenal is a branch of the inferior phrenic artery;
the middle adrenal is a branch of the abdominal aorta;
the inferior adrenal arises from the renal artery.

Diagram of blood supply to the adrenal glands.

The continuation of the superior and middle adrenal arteries are capillaries that penetrate the cortex and end in the medulla as venous sinuses. This means that hormones synthesized by the cells of the cortex leave the cortex, passing through the medulla. GCS stimulate the release of adrenaline from chromaffin cells. This phenomenon explains the combined involvement of the organ in the development of stressful situations.

A continuation of the inferior adrenal artery is the cerebral artery, which supplies arterial blood only to the medulla, bypassing the cortex, and ends at the cerebral venous sinuses. Venous blood from them is sent to the central vein, from here the outflow from the organ begins.

Venous blood from the adrenal glands flows into the inferior hollow system.

From the central veins, blood enters the adrenal veins. The latter emerge from the gates of the glands and flow into the renal vein on the left and into the inferior vena cava on the right.

Lymph drainage occurs through lymphatic vessels adjacent to the lumbar lymph nodes. The latter lie around the aorta and inferior vena cava.

The adrenal glands receive innervation from branches of the celiac plexus that form the adrenal plexus. The latter includes fibers of the sympathetic, vagus and phrenic nerves.

Adrenal diseases

All diseases of the adrenal glands can be divided into 2 large groups - pathology of the cortex and medulla. The classification is based on the functional state of the organ, which can be increased (hyperfunction), decreased (hypofunction) or not changed. There is a separate group of diseases characterized by dysfunction of the adrenal cortex. With the latter, there is an increased formation of some hormones and insufficient formation of other hormones. With dysfunction of the adrenal cortex, there is an excess production of some hormones and a lack of others.

Diseases of these glands:

Adrenal health	Diseases
Hypercortisolism (cortical hyperfunction)	Itsenko-Cushing's disease and syndrome; primary hyperaldosteronism; androsteroma (virilizing tumor); corticosteroma (feminizing tumor); mixed tumors (overproduction of several hormones)
Hypocorticism (hypofunction of the cortex)	primary; secondary
Cortical dysfunction	deficiency of P450 fractions; Star protein deficiency (Prader syndrome)
Eucorticism (cortical function is not impaired)	Hormonally inactive adrenal tumors (benign, malignant)
Pathology of the medulla	Pheochromocytoma (benign, malignant)

Diagnosis of these diseases is carried out according to symptoms, results of laboratory and instrumental studies.

For this purpose, hormonal tests are used to determine the level of hormones and their metabolites. The indicator of water and electrolyte balance is also important. In instrumental diagnostics, various techniques for visualizing the adrenal glands are used. These include CT and MRI.

To treat diseases of the adrenal glands, conservative and surgical therapy is used. The first group of methods includes:

replacement therapy (for hypofunction);
the use of drugs (for hyperfunction) that have an inhibitory effect on certain hormones (for example, aldosterone).

Surgical treatment is used for adrenal tumors.

Endocrine system

Structure of the endocrine system

Endocrine system is one of the regulatory-integrating systems of the body along with the cardiovascular, nervous and immune systems, acting with them in the closest unity. It is responsible for the regulation of the most important vegetative functions of the body: growth, reproduction, reproduction and differentiation of cells, metabolism and energy, secretion, excretion, absorption, behavioral reactions and others. In general, the function of the endocrine system can be defined as maintaining homeostasis in the body.

The endocrine system consists of:

· endocrine glands - organs that produce hormones (thyroid gland, adrenal glands, pineal gland, pituitary gland and others);

· endocrine parts of non-endocrine organs (islets of Langerhans of the pancreas);

· single hormone-producing cells located diffusely in various organs - diffuse endocrine system.

General principles of the structural and functional organization of the endocrine glands:

· do not have excretory ducts, as they secrete hormones into the blood;

· have a rich blood supply;

· have capillaries of fenestrated or sinusoidal type;

· are organs of the parenchymal type, mostly formed by epithelial tissue that forms cords and follicles;

· in endocrine organs the parenchyma predominates, while the stroma is less developed, that is, the organs are built economically;

· produce hormones - biologically active substances that have pronounced effects in small quantities.

Classification of hormones:

· proteins and polypeptides - hormones of the pituitary gland, hypothalamus, pancreas and some other glands;

· amino acid derivatives - thyroid hormones (thyroxine and triiodothyronine), adrenal medulla hormone adrenaline, serotonin produced by many endocrine glands and cells, and others;

· steroids (cholesterol derivatives) - sex hormones, adrenal hormones, vitamin D2 (calcitriol).

Features of the action of hormones:

· distance - can be produced far from target cells;

· specificity;

· selectivity;

· high activity in small doses.

Mechanism of action of hormones

Once in the blood, hormones and its current reach regulated cells, tissues, and organs, which are called targets. You can select two main mechanisms of hormone action:

· First mechanism - the hormone binds to complementary receptors on the cell surface and changes the spatial orientation of the receptor. The latter are transmembrane proteins and consist of a receptor and a catalytic part. When binding to a hormone, the catalytic subunit is activated, which begins the synthesis of a secondary messenger (messenger). The messenger activates a whole cascade of enzymes, which leads to changes in intracellular processes. For example, adenylate cyclase produces cyclic adenosine monophosphate, which regulates a number of processes in the cell. Hormones of a protein nature function according to this mechanism, the molecules of which are hydrophilic and cannot penetrate cell membranes.

· Second mechanism - the hormone penetrates the cell, binds to the receptor protein and, together with it, enters the nucleus, where it changes the activity of the corresponding genes. This leads to changes in cell metabolism. The same hormones can act on individual organelles, for example, mitochondria. This mechanism is used by fat-soluble steroid and thyroid hormones, which, due to their lipotropic properties, easily penetrate into the cell through its membrane.

Classification of endocrine glands according to a hierarchical principle:

· central - hypothalamus, pineal gland and pituitary gland. They control the activities of other (peripheral) endocrine glands;

· peripheral, which exercise direct control over the most important functions of the body.

Depending on whether they are under the regulating action of the pituitary gland or not, peripheral endocrine glands are divided into two groups:

· 1 group- adenopituitary-independent calcitoninocytes of the thyroid gland, parathyroid gland, adrenal medulla, islet apparatus of the pancreas, thymus, endocrine cells of the diffuse endocrine system;

· 2nd group- adenopituitary-dependent thyroid gland, adrenal cortex, gonads.

By level of structural organization:

· endocrine organs (thyroid and parathyroid glands, adrenal glands, pituitary gland, pineal gland);

· endocrine sections or tissues within organs that combine endocrine and non-endocrine functions (hypothalamus, islets of Langerhans of the pancreas, reticuloepithelium and Hassal's bodies in the thymus, Sertoli cells of the testicular convoluted tubules and testicular follicular epithelium);

· cells of the diffuse endocrine system.

The structure of the hypothalamus

Hypothalamus is the center for the regulation of autonomic functions and the highest endocrine center. It has a transadenopituitary effect (through stimulation of the pituitary gland's production of tropic hormones) on the adenopituitary-dependent endocrine glands and a paraadenopituitary effect on the adenopituitary-independent glands. The hypothalamus controls all visceral functions of the body and combines nervous and endocrine regulatory mechanisms.

The hypothalamus occupies the basal part of the diencephalon - it is located under the visual thalamus (thalamus), forming the bottom of the 3rd ventricle. The cavity of the 3rd ventricle continues into the funnel directed towards the pituitary gland. The wall of this funnel is called the pituitary stalk. Its distal end continues into the posterior lobe of the pituitary gland (neurohypophysis). Anterior to the pituitary stalk, the thickening of the bottom of the 3rd ventricle forms the median eminence (medial eminence), containing the primary capillary network.

The hypothalamus contains:

front;

medium (mediobasal);

· posterior sections.

The bulk of the hypothalamus consists of nerve and neurosecretory cells. They form more than 30 nuclei.

Anterior hypothalamus contains the largest paired supraoptic and paraventricular nuclei, as well as a number of other nuclei. The supraoptic nuclei are formed mainly by large peptidecholinergic neurons. The axons of peptidecholinergic neurons pass through the pituitary stalk into the posterior lobe of the pituitary gland and form synapses on blood vessels - axovasal synapses. Neurons of the supraoptic nuclei secrete mainly antidiuretic hormone or vasopressin. The hormone is transported along the axon to the posterior lobe of the pituitary gland and accumulates in the extension of the axon, which lies above the axovasal synapse and is called Hering's storage body. If necessary, from here it enters the synapse and then into the blood. The target organs of vasopressin are the kidneys and arteries. In the kidneys, the hormone increases the reverse reabsorption of water (in the nephron tubules and collecting ducts) and thereby reduces the volume of urine, promoting fluid retention in the body and increasing blood pressure. In arteries, the hormone causes contraction of smooth muscle cells and an increase in blood pressure.

The paraventricular nuclei, along with large peptidecholinergic neurons, also contain small peptidadrenergic ones. The former produce the hormone oxytocin, which travels along axons to the Hering bodies of the posterior pituitary gland. Oxytocin causes synchronous contraction of the uterine muscles during childbirth and activates myoepithelial cells of the mammary gland, which increases milk secretion during feeding of the baby.

Middle hypothalamus contains a number of nuclei consisting of small neurosecretory peptidadrenergic neurons. The most important are the arcuate and ventromedial nuclei, forming the so-called arcuate-mediobasal complex. The neurosecretory cells of these nuclei produce adenohypophysotropic hormones that regulate the function of adenohypophysiotropic hormones. Hypophysiotropic releasing hormones are oligopeptides and are divided into two groups: liberins, which enhance the secretion of hormones by the adenohypophysis, and statins, which inhibit it. Gonadotropin-releasing hormone, corticoliberin, and somatoliberin have been isolated from the liberins. At the same time, only two statins are described: somatostatin, which suppresses the pituitary gland's synthesis of growth hormone, adrenocorticotropin and thyrotropin, and prolactinostatin.

Posterior hypothalamus includes mammillary bodies and perifornical nucleus. This department does not belong to the endocrine department; it regulates glucose levels and a number of behavioral reactions.

The structure of the pituitary gland

Adenohypophysis develops from the epithelium of the roof of the oral cavity, which is of ectodermal origin. At the 4th week of embryogenesis, an epithelial protrusion of this roof forms in the form of Rathke's pouch. The proximal part of the pouch is reduced, and the bottom of the 3rd ventricle protrudes towards it, from which the posterior lobe is formed. The anterior lobe is formed from the anterior wall of Rathke's pouch, and the intermediate lobe is formed from the posterior wall. The connective tissue of the pituitary gland is formed from mesenchyme.

Functions of the pituitary gland:

· regulation of the activity of the adenohypophyseal-dependent endocrine glands;

· accumulation of vasopressin and oxytocin for the neurohormones of the hypothalamus;

· regulation of pigment and fat metabolism;

· synthesis of a hormone that regulates body growth;

· production of neuropeptides (endorphins).

The pituitary gland is a parenchymal organ with weakly developed stroma. It consists of the adenohypophysis and neurohypophysis. The adenohypophysis includes three parts: the anterior, intermediate lobes and the tuberal part.

Anterior lobe consists of epithelial strands of trabeculae, between which fenestrated capillaries pass. The cells of the adenohypophysis are called adenocytes. There are 2 types of them in the anterior lobe:

· Chromophilic adenocytes are located along the periphery of trabeculae and contain secretion granules in the cytoplasm, which are intensely stained with dyes and are divided into:

· oxyphilic

· basophilic.

Oxyphilic adenocytes are divided into two groups:

· somatotropocytes produce growth hormone (somatotropin), which stimulates cell division in the body and its growth;

· lactotropocytes produce lactotropic hormone (prolactin, mammotropin). This hormone enhances the growth of the mammary glands and their secretion of milk during pregnancy and after childbirth, and also promotes the formation of the corpus luteum in the ovary and its production of the hormone progesterone.

Basophilic adenocytes are also divided into two types:

· thyrotropocytes - produce thyroid-stimulating hormone, this hormone stimulates the production of thyroid hormones by the thyroid gland;

· gonadotropocytes are divided into two types - follitropocytes produce follicle-stimulating hormone, in the female body it stimulates the processes of oogenesis and the synthesis of female sex hormones estrogen. In the male body, follicle-stimulating hormone activates spermatogenesis. Luthropocytes produce luteotropic hormone, which in the female body stimulates the development of the corpus luteum and its secretion of progesterone.

Another group chromophilic adenocytes - adrenocorticotropocytes. They lie in the center of the anterior lobe and produce adrenocorticotropic hormone, which stimulates the secretion of hormones by the zona fasciculata and reticularis of the adrenal cortex. Thanks to this, adrenocorticotropic hormone is involved in the body’s adaptation to starvation, injury, and other types of stress.

Chromophobe cells are concentrated in the center of the trabeculae. This heterogeneous group of cells in which the following varieties:

· immature, poorly differentiated cells that play the role of cambium for adenocytes;

· chromophilic cells that have secreted a secret and therefore are not stained at the moment;

· follicular stellate cells - small in size, having small processes with the help of which they connect to each other and form a network. Their function is not clear.

Average share consists of discontinuous strands of basophilic and chromophobe cells. There are cystic cavities lined with ciliated epithelium and containing a colloid of a protein nature, in which there are no hormones. Adenocytes of the intermediate lobe produce two hormones:

· melanocyte-stimulating hormone, it regulates pigment metabolism, stimulates the production of melanin in the skin, adapts the retina to vision in the dark, activates the adrenal cortex;

Lipotropin, which stimulates fat metabolism.

The tuberal zone is formed by a thin cord of epithelial cells surrounding the epiphyseal stalk. The pituitary portal veins pass through the tuberal lobe, connecting the primary capillary network of the medial eminence with the secondary capillary network of the adenohypophysis.

Posterior lobe or the neurohypophysis has a neuroglial structure. Hormones are not produced in it, but only accumulate. Vasopressin and oxytocin neurohormones of the anterior hypothalamus enter here along the axons and are deposited in the Hering bodies. The neurohypophysis consists of ependymal cells - pituicytes and axons of neurons of the paraventricular and supraoptic nuclei of the hypothalamus, as well as blood capillaries and Hering bodies - extensions of the axons of neurosecretory cells of the hypothalamus. Pituycytes occupy up to 30% of the volume of the posterior lobe. They have a branched shape and form three-dimensional networks, surrounding the axons and terminals of neurosecretory cells. The functions of pituicytes are trophic and supporting functions, as well as regulation of the release of neurosecretion from axon terminals into hemocapillaries.

The blood supply to the adenohypophysis and neurohypophysis is isolated. The adenohypophysis is supplied with blood from the superior pituitary artery, which enters the medial eminence of the hypothalamus and breaks up into the primary capillary network. On the capillaries of this network, the axons of neurosecretory neurons of the mediobasal hypothalamus, which produce releasing factors, end at axovasal synapses. The capillaries of the primary capillary network and axons, together with synapses, form the first neurohemal organ of the pituitary gland. The capillaries then collect into portal veins, which go to the anterior lobe of the pituitary gland and there break up into a secondary capillary network of fenestrated or sinusoidal type. Through it, releasing factors reach adenocytes and adenohypophysis hormones are released here. These capillaries collect in the anterior pituitary veins, which carry blood with adenohypophysial hormones to the target organs. Since the capillaries of the adenohypophysis lie between two veins (portal and pituitary), they belong to the “miraculous” capillary network. The posterior lobe of the pituitary gland is supplied by the inferior pituitary artery. This artery breaks down into capillaries, on which axovasal synapses of neurosecretory neurons are formed - the second neurohemal organ of the pituitary gland. The capillaries collect in the posterior pituitary veins.

The structure of the pineal gland

Pineal gland located between the anterior tubercles of the quadrigeminal. In embryogenesis, it is formed at the 5-6th week of intrauterine development, as a protrusion of the roof of the diencephalon.

The structure of the pineal gland

Pineal gland- parenchymal lobular organ. The outside is covered with a capsule of loose fibrous connective tissue, from which septa extend, dividing the epiphysis into lobules. The parenchyma of the lobules is formed by anastomosing cellular cords, islets and follicles and is represented by two types of cells: pinealocytes and gliocytes. Pinealocytes make up up to 90% of cells. Gliocytes of the pineal gland, obviously related to astroglia, make up up to 5% of all parenchyma cells. They are distributed throughout the parenchyma of the lobule, sometimes forming groups of 3-4 cells. The function of gliocytes is supporting, trophic, regulatory.

The pineal gland functions most actively at a young age. With aging, the organ shrinks; phosphates and calcium carbonates can be deposited in it in the form of crystals, which are associated with the organic matrix of destroyed cells (epiphyseal sand).

The pineal gland synthesizes the following hormones:

· Serotonin and melatonin regulate the body's "biological clock". Hormones are derivatives of the amino acid tryptophan. First, serotonin is synthesized from tryptophan, and melatonin is formed from the latter. It is an antagonist of melanocyte-stimulating hormone of the pituitary gland, produced at night, inhibits the secretion of GnRH, thyroid hormones, adrenal hormones, growth hormone, and sets the body to rest. In boys, melatonin levels decrease during puberty. In women, the highest level of melatonin is determined during menstruation, and the lowest during ovulation. Serotonin production significantly predominates during the daytime. At the same time, sunlight switches the pineal gland from the formation of melatonin to the synthesis of serotonin, which leads to awakening and wakefulness of the body (serotonin is an activator of many biological processes).

· About 40 peptide hormones, of which the most studied are:

· hormone that regulates calcium metabolism;

· the hormone arginine-vasotocin, which regulates arterial tone and inhibits the pituitary gland's secretion of follicle-stimulating hormone and luteinizing hormone.

It has been shown that pineal gland hormones suppress the development of malignant tumors. Light is the function of the pineal gland, and darkness stimulates it. A neural pathway has been identified: retina - retinohypothalamic tract - spinal cord - sympathetic ganglia - pineal gland.

Thus, functional activity is most pronounced in childhood. At this time, it prevents premature puberty, allowing the child’s body to become physically stronger. The functions of the pineal gland are suppressed by light exposure. Obviously, excessive insolation inhibits the inhibitory effect of the pineal gland on the gonads, which explains the earlier puberty of children in southern countries.

The structure of the adrenal glands

Functions of the adrenal glands:

· production of mineralocorticoids (aldosterone, deoxycorticosterone acetate and others), regulating water-salt metabolism, as well as activating inflammatory and immune reactions. Mineralocorticoids stimulate sodium reabsorption by the kidneys, which leads to water retention in the body and increased blood pressure;

· production of glucocorticoids (cortisol, hydrocortisone and others). These hormones increase blood glucose levels by synthesizing it from the breakdown products of fats and proteins. Hormones suppress inflammatory and immune reactions, which is used in medicine to treat autoimmune, allergic reactions, and so on;

· production of sex hormones, mainly androgens (dehydroepiandrosterone and androstenedione), which have a weak androgenic effect, but when released under stress, stimulate muscle growth. The production and secretion of androgens is stimulated by adrenocorticotropic hormone;

· The medulla produces catecholamines - the hormone adrenaline and the neurotransmitter norepinephrine, which are produced under stress.

Thus, the adrenal glands are vital organs; their complete removal or destruction by a pathological process leads to changes incompatible with life and death.

The adrenal glands are paired parenchymal organs of the zonal type. The outside is covered with a capsule of dense fibrous unformed tissue, from which layers extend deeper into the organ - trabeculae. The capsule contains smooth myocytes, autonomic ganglia, accumulations of fat cells, nerves, and blood vessels. The capsule and layers of loose fibrous unformed connective tissue form the stroma of the organ. The parenchyma is represented by a collection of cells: corticocytes in the cortex and chromaffinocytes in the medulla.

The adrenal glands are clearly divided into two structurally and functionally distinct zones:

· The cortex consists of several zones:

· the subcapsular zone is formed by small, poorly differentiated corticocytes, which play the role of cambium for the cortex;

· zona glomerulosa makes up 10% of the adrenal cortex. It is formed by small corticocytes that form glomeruli. They have a moderately developed smooth endoplasmic reticulum where corticosteroid hormones are synthesized. The functions of the zona glomerulosa are the production of mineralocorticoids, or more precisely, in this zone only the final stage of the biosynthesis of mineralocorticoids occurs from their precursor corticosterone, which comes here from the zona fasciculata;

· zona fasciculata is the most pronounced zone of the adrenal cortex. It is formed by large oxyphilic corticocytes that form cords and bundles. Between the bundles in thin layers of loose fibrous connective tissue lie sinusoidal capillaries. There are two types of tufted corticocytes: dark and light. This is one type of cells that are in different functional states. The function of the zona fasciculata is the production of glucorticoids (mainly cortisol and cortisone).

The reticular zone occupies about 10-15% of the entire cortex. Consists of small cells that lie in the form of a network. In the reticular zone, glucorticoids and male sex hormones are formed, in particular, androstenedione and dehydroepiandrosterone, as well as in small quantities female sex hormones (estrogens and progesterone). Androgens of the adrenal cortex, unlike androgens of the gonads, have a weak androgenic effect, but their anabolic effect on skeletal muscles is preserved, which has important adaptive significance.

Adrenal hormones are fat-soluble substances and easily penetrate the cell membrane, so there are no secretory granules in corticocytes.

· Brain matter separated from the cortex by a thin capsule of loose fibrous connective tissue. It is formed by an accumulation of chromaffinocyte cells, which are well stained with chromium salts.

These cells are divided into two types:

· large light cells producing the hormone adrenaline (A-cells), containing moderately electron-dense granules in the cytoplasm;

· dark small chromatoffinocytes (HA cells), containing a large number of dense granules, they secrete norepinephrine.

Autonomic neurons (ganglion cells) and supporting cells, a type of neuroglia, are also found in the medulla. They surround chromaffinocytes with their processes.

Blood supply to the adrenal glands

The arteries included in the capsule disintegrate into arterioles, forming a dense subcapsular network, and capillaries of fenestrated and sinusoidal type, supplying blood to the cortex. From the reticular zone, capillaries penetrate into the medulla, where they turn into wide sinusoids, merging into venules. The venules become veins, forming the venous plexus of the medulla. From the subcapsular network, arterioles also penetrate into the medulla, disintegrating into capillaries.

Pineal body

The pineal body, corpus pineale, is located above the superior colliculi of the midbrain roof plate, being connected to the thalami through the habenulae. It is a small, oval-shaped and reddish-colored body, the narrower end of which is directed downward and backward. Body length 7 - 10 mm, diameter 5 - 7 mm. Cells grouped in the form of strands have secretory properties. The pineal body is larger in early childhood (in women it is also larger than in men), but even before the onset of puberty, involution phenomena are detected, the first signs of which are noticeable already in the 7th year of life.

Function. The function of the pineal gland is not completely understood. Extirpation of the gland in young animals entails rapid skeletal growth with premature and exaggerated development of the gonads and secondary sexual characteristics. Therefore, one must think that the gland has an inhibitory effect on these functions.

Development. The pineal body develops as an initially hollow outgrowth from the upper wall of the diencephalon (the future third ventricle).

Vessels and nerves. Several branches from a. approach the pineal body. chorioidea posterior (branch of A. cerebri posterior), a. cerebelli and a. cerebri media. The sympathetic fibers included in the corpus pineale are apparently intended to innervate blood vessels.

Adrenal

Adrenal gland, glandula suprarenalis s. adrenalis, a paired organ, lies in the retroperitoneal tissue above the upper end of the corresponding kidney. The mass of the adrenal gland is about 4 g; With age, no significant enlargement of the adrenal gland is observed. Dimensions: vertical - 30 - 60 mm, transverse - about 30 mm, anteroposterior - 4 - 6 mm. The outer color is yellowish or brownish. The right adrenal gland, with its lower pointed edge, covers the upper pole of the kidney, while the left adrenal gland is adjacent not so much to the pole of the kidney, but to the part of the inner edge of the kidney closest to the stripe.

One or more grooves are noticeable on the anterior surface of the adrenal glands - this is the gate, hilus, through which the adrenal vein exits and the arteries enter.

Structure. The adrenal gland is covered with a fibrous capsule that sends individual trabeculae deep into the organ. The adrenal gland consists of two layers: the cortex, yellowish in color, and the medulla, softer and darker brownish in color. In their development, structure and function, these two layers differ sharply from each other.

The cortex consists of three zones that produce various hormones. The medulla consists of cells that produce adrenaline and norepinephrine. These cells are intensely stained with chromium salts in a yellow-brown color (chromaffin). It also contains a large number of unmyelinated nerve fibers and ganglion (sympathetic) nerve cells.

Development. The cortex belongs to the so-called interrenal system, originating from the mesoderm, between the primary kidneys (hence the name of the system).

The medulla comes from the ectoderm, from sympathetic elements (which are then divided into sympathetic nerve cells and chromaffin cells). This is called the adrenal, or chromaffin, system. The interrenal and chromaffin systems in lower vertebrates are independent of each other; in higher mammals and humans they are combined into one anatomical organ - the adrenal gland.

Function. According to the structure of two dissimilar substances - the cortex and the medulla - the adrenal gland, as it were, combines the functions of two glands. The medulla releases norepinephrine and adrenaline into the blood (currently obtained synthetically), which maintains the tone of the sympathetic system and has vasoconstrictor properties.

The cortex is the main site of lipid production (especially lecithin and cholesterol) and appears to be involved in the neutralization of toxins resulting from muscle work and fatigue.

There are also indications that the adrenal cortex secretes hormones (steroids) that affect water-salt, protein and carbohydrate metabolism, and special hormones similar to male (androgens) and female (estrogens) sex hormones.

The combined action of both parts of the adrenal gland is facilitated by their common blood supply and innervation. In particular, relaxation of the sphincters present in the adrenal veins leads to the simultaneous entry into the general circulation of both medullary and cortical hormones.

Vessels and nerves. The adrenal glands receive three pairs of arterial branches: the superior adrenal arteries (from a. phrenica inferior), middle (from aorta abdominalis) and lower (from a. renalis). All of them, anastomosing among themselves, form a network in the adrenal capsule. Venous blood, passing through the wide venous capillaries (sinusoids) of the medulla, usually flows through one trunk, v. suprarenalis (centralis), emerging from the portal of the adrenal gland and flowing on the right into v. cava inferior, and on the left (longer trunk) into v. renalis sinistra. Lymphatic vessels are directed to the lymph nodes located near the aorta and inferior vena cava.

The nerves come from the n.splanchnicus major (through the plexus coeliacus and plexus renalis).

4.64. Concepts about the organs of the immune system, their classification. Regularities of their structure. Concept of immune response.

The organs of the immune system provide protection of the body (immunity) from genetically foreign cells and substances coming from outside or formed in the body. They are classified into: central – thymus gland (thymus); peripheral - bone marrow, lymph nodes, spleen, lymphoid nodules of the ileum and appendix, respiratory system, walls of hollow organs.

The thymus gland, thymus, is covered with a capsule that extends interlobular septa into the gland. The lobule consists of medulla and cortex. The cortex is formed by a network of epithelial cells, in the loops of which lie lymphocytes - T (thymocytes). In the medulla, epithelial cells flatten and become keratinized, forming thymic corpuscles. Functions: T - lymphocytes acquire protective properties in the thymus due to the hormone produced in epithelial cells.

Bone marrow, medulla ossium, comes in two types: red bone marrow and yellow bone marrow. Red bone marrow, medulla ossium rubra, looks like a tender red mass consisting of reticular tissue, in the loops of which there are stem cells, osteoblasts, osteoclasts; has a red color due to blood vessels and blood elements. Yellow bone marrow, medulla ossium flava, consists mainly of fat cells. Functions: hematopoiesis, biological protection; nutrition, development and bone growth.

Lymph nodes, nodi lymphatici, are covered with a connective tissue capsule, from which capsular trabeculae extend inward; There are gates through which arteries and nerves enter and veins exit. There is a lobular structure, the stroma consists of reticular-connective tissue, in the loops of which there are lymphocytes; parenchyma consists of cortex and medulla. Lymph nodes containing B lymphocytes are located in the cortex. The medulla - pulpy cords of cluster B - lymphocytes. Between the capsule, trabeculae and parenchyma there are gaps - lymphatic sinuses through which lymph flows; foreign particles accumulate in the parenchyma. Functions: are organs of lymphopoiesis and antibody formation.

The spleen, lien, has its own connective capsule with an admixture of elastic and non-striated muscle fibers. The capsule continues inward in the form of crossbars, forming a skeleton. Between the trabeculae there is the splenic pulp with lymph nodes, which consists of reticular tissue, the loops of which are filled with leukocytes, lymphocytes, and platelets that are already disintegrating. Function: contains lymphocytes involved in immunological reactions; spent blood cells die in the pulp; Iron from red blood cells goes to the liver, where it serves as material for the synthesis of bile pigments.

Table of contents of the topic "Adrenal glands. Endocrine parts of the gonads, pancreas.":

Adrenal gland function. Vessels (blood supply) of the adrenal glands. Nerves (innervation) of the adrenal glands.

According to the structure of two dissimilar substances - cortical and cerebral- The adrenal gland combines the functions of two glands. The medulla releases norepinephrine and adrenaline into the blood (currently obtained synthetically), which maintains the tone of the sympathetic system and has vasoconstrictor properties. The cortex is the major site of lipid production (especially lecithin and cholesterol) and appears to be involved in the neutralization of toxins resulting from muscle work and fatigue.

There are also indications that adrenal cortex secretes hormones (steroids) that affect water-salt, protein and carbohydrate metabolism, and special hormones similar to male (androgens) and female (estrogens) sex hormones.

Vessels (blood supply) of the adrenal glands. Nerves (innervation) of the adrenal glands. The adrenal glands receive three pairs of arterial branches: the superior adrenal arteries (from a. phrenica inferior), middle (from aorta abdominalis) and lower (from a. renalis). All of them, anastomosing with each other, form a network in the adrenal capsule. Venous blood, passing through the wide venous capillaries (sinusoids) of the medulla, usually flows through one trunk, v. suprarenalis (centralis), emerging from the gate of the adrenal gland and flowing into the v. on the right. cava inferior, and on the left (longer trunk) in v. renalis sinistra. Lymphatic vessels are directed to the lymph nodes located near the aorta and inferior vena cava.

Nerves come from n. splanchnicus major (via plexus coeliacus ii plexus renalis).