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Adrenal Hormones and Their Functions

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Adrenal glands are small paired endocrine glands located in the retroperitoneal space. The structure of these organs is quite complicated. In each gland secrete two parts: the cortex and the medulla. These anatomically close structures have a different embryonic origin.

Adrenal glands

Fig.1 - Location of the adrenal glands in the body.

The bark begins to be laid on the fifth week of intrauterine development of the fetus. First, a fetal( primary) tissue is formed, formed by large acidophilic endocrinocytes. The bark undergoes several transformations in the subsequent embryogenesis and after the birth of the child to the light. The formation of this part of the adrenal gland is completed only after puberty.

The cortical portion of the adrenal glands develops from cells that are close to the gonad rudiments. With this connect the ability of endocrine cells( a reticular zone) to synthesize sex steroids.

The cerebral part of the gland is laid on the sixth week of embryogenesis. Endocrine cells originate from a special embryonic structure - a neural crest. This rudiment is the precursor of the sympathetic ganglia of the autonomic nervous system.

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Contents

  • 1 Structure of the bark and medulla
  • 2 Adrenal glands
    • 2.1 Mineralcorticoids
    • 2.2 Glucocorticoids
    • 2.3 Adrenal androgen adenoses
    • 2.4 Catecholamines

Structure of the cortex and medulla

The cerebral adrenal medulla is almost uniform. A crust consists of three layers. Allocate:

  • glomerular zone;
  • beam zone;
  • net area.

The structure of the adrenal glands

Fig.2 - The structure of the adrenal glands.

In the cortical part of the adrenal glands are extremely important for the functioning of the body's hormones. Violation of the synthesis of these substances leads to the development of serious diseases. Complete cessation of the cortex may cause the death of the patient.

The glomerular zone is the most superficial layer. Endocrine cells of this region are located directly under the capsule of the adrenal gland. The interdependence of adrenocorticocytes resembles arcades( or tangles).Cells have a well-developed endoplasmic reticulum.

In the fascicle there are cubic endocrine cells. They form vertically stretched structures( strands).In cells, the endoplasmic reticulum is well developed, the lipids and vacuoles are determined in the cytoplasm.

The mesh zone consists of small endocrine cells of various shapes. These endocrinocytes form a loose network. Within the cells, there are few lipid inclusions, but a lot of free ribosomes are found.

The brain substance consists of chromaffinocytes and supporting neuroglial cells. Endocrine cells have a rounded shape. In the central part of the adrenal glands, catecholamines are synthesized. These substances play an important role in adaptation reactions. The starting material for the synthesis of all catecholamines is the amino acid tyrosine.

Adrenal glands

A whole series of steroid hormones are synthesized in the glomerular, fascicular, reticular zone. The starting material for the synthesis of these substances are the cholesterol molecules.

In the glomerular zone, aldosterone and other mineralocorticoids are synthesized. These hormones participate in water-salt metabolism. The effect on the activity of endocrine cells is exerted by the renin-angiotensin system.

In the beam zone, glucocorticoids are formed. This group includes cortisol and its analogs. The beam zone is regulated by the hypothalamic-pituitary region of the brain. Synthesis of glucocorticoids depends on the concentration in the blood of adrenocorticotropic hormone( ACTH).

The mesh zone is the source of the androgen adrenals. Here, dehydroepiandrosterone( DHS), DHS-sulfate and androstenedione are formed. These hormones are rather weak androgens. They can also act as precursors of other sex steroids. The activity of the endocrine cells of the reticular zone depends on the concentration of tropic hormones in the pituitary gland.

In the brain part of the adrenal glands, dopamine, epinephrine, noradrenaline are synthesized. These catecholamines are released in response to stress factors( pain, fear, etc.).

Mineralocorticoids

The most active hormone of this group is aldosterone. Also mineralocorticoids include deoxycorticosterone and others. These biologically active substances change the concentration of electrolytes in the blood plasma. They affect the renal tubules( distal convoluted and collecting).

Action of aldosterone and its analogues:

  • increase in reabsorption( sodium retention);
  • increase in excretion of potassium and hydrogen.

The delay of sodium ions helps to increase the volume of circulating blood. This leads in turn to an increase in systemic blood pressure.

Glucocorticoids

Cortisol and its analogs are vital hormones. Without these substances, the existence of the human body is impossible.

Glucocorticoids in the body:

  • increase blood pressure;
  • enhances the production of glucose from proteins and fats;
  • increase blood glucose levels;
  • accelerate the excretion of potassium and calcium ions;
  • suppress the capture of calcium ions in the digestive tract;
  • provokes a decrease in bone mineral density;
  • suppresses inflammatory reactions;
  • reduce the immune response;
  • suppresses allergic reactions;
  • activate the cerebral cortex.

Cortisol promotes the redistribution of adipose tissue. In high concentrations, this hormone makes the skin more vulnerable and thin. Also, cortisol in men reduces the amount of muscle tissue.

Adrenal androgen adenoses

Adrenal androgen adrenal glands have an effect on the body in childhood and after puberty. Androstenedione and its analogues are 10-20 times weaker than testosterone. In the body of men, these androgens can be converted into estrogens( estrone).Female sex steroids in the male body are synthesized from androgens in the liver and adipose tissue. In men with obesity, the formation of estrogens can be quite significant. In severe cases, this condition is manifested by gynecomastia, infertility, impotence and other disorders.

Also adrenostione adrenal glands can be modified to testosterone. If a man for some reason( oncology, trauma) is castrated, it is the adrenal androgens become the only source of sex steroids. In this case, hypertrophy of the mesh cortex zone usually develops. Completely close the deficit of androgens when removing the testicles of the adrenal glands can not. Probably, in most situations such patients are advisable to carry out hormone replacement therapy with testosterone and its analogues.

The role of androgens of the adrenal glands:

  • promotes hair growth in androgen-dependent zones;
  • are involved in the formation of secondary sexual characteristics of men;
  • supports the activity of the sebaceous glands of the skin;
  • are one of the factors determining sexual behavior and libido;
  • affect the functioning of the central nervous system.

Catecholamines

Norepinephrine and adrenaline are stress hormones. They are in large quantities thrown into the blood in those moments when a person experiences fear or anger. Catecholamines are responsible for the behavioral reactions of "struggle" and "defense".At a critical moment, these hormones should help the body survive.

Epinephrine and norepinephrine:

  • increases pulse;
  • increase systemic blood pressure;
  • dilates the bronchi;
  • increases the respiratory volume;
  • suppress digestion;
  • reduce sphincters( bladder, intestines);
  • cause pupil dilated;
  • increases perspiration;
  • promote ejaculation.

The action of catecholamines on the body is very short. After release into the blood, these hormones quickly break down. Effects of epinephrine and norepinephrine in full only a few minutes.

Doctor-endocrinologist Tsvetkova IG

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