Adrenals are an important part of the endocrine system along with the thyroid and germ cells. It synthesizes more than 40 different hormones involved in the metabolism. One of the most important systems of regulation of vital activity of the human body is the endocrine system. It consists of the thyroid and pancreatic glands, sex cells and adrenal glands. Each of these organs is responsible for the production of certain hormones.
What hormones secret the adrenal glands
Adrenal glands are a pair of glands located in the retroperitoneal space a little above the kidneys. The total weight of organs is 7-10 g. The adrenal glands are surrounded by fatty tissue and the renal fascia close to the upper pole of the kidney.
The form of the organs is different - the right adrenal gland resembles a triangular pyramid, the left one looks like a crescent. The average organ length is 5 cm, width 3-4 cm, thickness - 1 cm. The color is yellow, the surface is tuberous.
They are 2 independent glands of internal secretion, they have different cellular composition, different origin and perform different functions, despite the fact that they are united into one organ.
It is interesting that the glands develop independently of each other. The cortical substance in the embryo begins to form at the 8th week of development, and the cerebral substance only at the 12-16th week.
In the cortical layer, up to 30 corticosteroids are synthesized, which are otherwise called steroid hormones. And the adrenal glands secrete the following hormones, which divide them into 3 groups:
- glucocorticoids - cortisone, cortisol, corticosterone. Hormones affect carbohydrate metabolism and have a manifesting effect on inflammatory reactions;
- mineralocorticoids - aldosterone, deoxycorticosterone, they control water and mineral metabolism;Sex hormones - androgens. They regulate sexual functions and affect sexual development.
Steroid hormones break down fairly quickly in the liver, passing into a water-soluble form, and are eliminated from the body. Some of them can be obtained by artificial means. In medicine, they are actively used in the treatment of bronchial asthma, rheumatism, articular ailments.
The brain layer synthesizes catecholamines - norepinephrine and adrenaline, the so-called stress hormones secreted by the adrenal glands. In addition, here are produced peptides, which regulate the activity of the central nervous system and gastrointestinal tract: somatostatin, beta-enkephalin, vasoactive instentinal peptide.
The cerebral substance is located centrally in the adrenal gland, formed by chromaffin cells. The organ receives the signal about the production of catecholamines from the preganglionic fibers of the sympathetic nervous system. Thus, the brain substance can be considered as a specialized sympathetic plexus, which, however, carries out the release of substances directly into the bloodstream bypassing the synapse.
The half-life of stress hormones is 30 seconds. These substances are very quickly destroyed.
In general, the effect of hormones on the state and behavior of a person can be described using the theory of a rabbit and a lion. A person who has little norepinephrine synthesized in a stressful situation reacts to a danger like a rabbit - feels fear, turns pale, loses the ability to make decisions, and assess the situation. A person whose ejection of norepinephrine is high behaves like a lion - experiencing anger and fury, does not feel danger and acts under the influence of a desire to suppress or destroy.
The scheme for the formation of catecholamines is as follows: an external signal activates the stimulus acting on the brain, which causes excitation of the posterior nuclei of the hypothalamus. The latter is a signal for the excitation of sympathetic centers in the thoracic region of the spinal cord. From there, along the preganglionic fibers, the signal enters the adrenal glands, where the synthesis of noradrenaline and epinephrine occurs. Then the hormones are released into the blood.
Adrenaline affects the human body as follows:
- increases heart rate and strengthens it;
- improves concentration, speeds up mental activity;
- provokes spasm of small vessels and "unimportant" organs - skin, kidneys, intestines;
- accelerates metabolic processes, promotes rapid disintegration of fats and the burning of glucose. With short-term exposure, it contributes to the improvement of cardiac activity, but with prolonged periods it is fraught with severe exhaustion;
- increases the respiratory rate and increases the depth of the entrance - is actively used for the relief of asthma attacks;
- reduces peristalsis of the intestine, but causes involuntary urination and defecation;
- helps to relax the uterus, reducing the likelihood of miscarriage.
The release of adrenaline into the blood often causes a person to perform heroic acts that are unthinkable in normal conditions. However, he is also the cause of "panic attacks" - causeless attacks of fear, accompanied by rapid heart rate and shortness of breath.
Noradrenaline is a precursor of epinephrine, its effect on the body is similar but not the same:
- noradrenaline increases peripheral vascular resistance, and also increases both systolic and diastolic pressure, so norepinephrine is sometimes called a release hormone;
- substance has a much stronger vasoconstrictive effect, but far less affects heart contractions;
- hormone helps to reduce the smooth muscles of the uterus, which stimulates delivery;
- on the musculature of the intestines and bronchi practically does not affect.
The action of noradrenaline and adrenaline is difficult to distinguish at times. A somewhat hypothetical effect of hormones can be imagined as follows: if a person decides to go to the roof and stand on the edge in fear of heights, norepinephrine is produced in the body, which helps to realize the intention. If such a person is tied violently to the edge of the roof, adrenaline works.
On the video about the main hormones of the adrenal glands and their functions:
The cortex is 90% of the adrenal gland. It is divided into 3 zones, each of which synthesizes its own group of hormones:
- glomerular zone - the thinnest surface layer;
- beam - middle layer;
- mesh area - adjacent to the brain substance.
This division can only be detected at a microscopic level, but the zones have anatomical differences and perform different functions.
The glomerular zone
Mineralocorticoids form in the glomerular zone. Their task is to regulate the water-salt balance. Hormones increase the absorption of sodium ions and reduce the absorption of potassium ions, which leads to an increase in the concentration of sodium ions in cells and the intercellular fluid and, in turn, increases the osmotic pressure. Thus, fluid retention in the body and increased blood pressure are provided.
In general, mineralocorticoids increase the permeability of capillaries and serous membranes, which provokes inflammation. The most important include aldosterone, corticosterone and deoxycorticosterone.
The synthesis of the substance is determined by the concentration of potassium and sodium ions in the blood: as the amount of sodium ions increases, the synthesis of the hormone is suspended, and the ions begin to be excreted in the urine. With an excess of potassium, aldosterone is produced in order to restore equilibrium, also the amount of tissue fluid and blood plasma affects the production of the hormone: when they increase, the secretion of aldosterone is suspended.
Regulation of synthesis and secretion of the hormone is carried out according to a certain scheme: in special cells of the afferent areoles of the kidney, renin is produced. It is the catalyst for the conversion of angiotensinogen into angiotensin I, which then under the influence of the enzyme passes into angiotensin II.The latter also stimulates the production of aldosterone.
Violations in the synthesis of renin or angiotensin, which is characteristic of various kidney diseases, leads to excessive release of the hormone and is the cause of high blood pressure, which is not amenable to usual antihypertensive treatment.
- Corticosterone - also involved in the regulation of water-salt metabolism, but much less active than aldosterone and is considered secondary. Corticosterone is produced both in the glomerular and in the beam zones and, in fact, refers to glucocorticoids.
- Deoxycorticosterone is also a secondary hormone, but in addition to participating in the restoration of the water-salt balance increases the endurance of skeletal muscles. Artificially synthesized substance is used for medical purposes.
The most known and significant in the group of glucocorticoids is cortisol and cortisone. Their value lies in the ability to stimulate the formation of glucose in the liver and suppress the consumption and use of the substance in extrahepatic tissues. Thus, plasma levels of glucose increase. In a healthy human body, the action of glucocorticoids is compensated by the synthesis of insulin, which reduces the amount of glucose in the blood. If this equilibrium is disturbed, the metabolism is disturbed: if insulin deficiency occurs, then the action of cortisol leads to hyperglycemia, and if glucocorticoid insufficiency is observed, glucose production decreases and hypersensitivity to insulin appears.
In hungry animals synthesis of glucocorticoids is accelerated in order to increase the processing of glycogen into glucose and provide the body with nutrition. At fed-in, output is kept at a certain level, since all the key metabolic processes are stimulated on a normal background of cortisol, while others manifest themselves as efficiently as possible.
Also the excess of hormones of this group does not allow leukocytes to accumulate in the inflammation zone and even strengthens it. As a result, people with this kind of diseases - diabetes mellitus, for example, do not heal wounds, there is a sensitivity to infections and so on. In bone tissue, hormones inhibit cell growth, which leads to osteoporosis.
The lack of glucocorticoids leads to a violation of water excretion and its excessive accumulation.
- Cortisol - the most powerful of the hormones of this group, is synthesized from 3 hydroxylases. In the blood is in free form or in the bound - with proteins. Of plasma 17-hydroxy corticoids, cortisol and its metabolic products account for 80%.The remaining 20% is cortisone and 11-descosicortisol. The secretion of cortisol determines the release of ACTH - its synthesis occurs in the pituitary gland, which in turn is provoked by impulses coming from different parts of the nervous system. The synthesis of the hormone affects the emotional and physical state, fear, inflammation, circadian cycle and so on.
- Cortisone - is formed by the oxidation of the 11 hydroxyl group of cortisol. It is produced in small amounts, and performs the same function: stimulates the synthesis of glucose from glycogen and inhibits lymphoid organs.
In the reticular zone of the adrenals, androgens are formed - sex hormones. Their effect is noticeably weaker than testosterone, but the significance is considerable, especially in the female body. The fact is that in the female body, dehydroepiandrosterone and androstenedione are the main male sex hormones - the necessary amount of testosterone is synthesized from dehydrodepindrosterone.
The synthesis of estrogens from androgens is carried out in peripheral adipose tissue. In post-menopause in the female body, this method becomes the only way to get sex hormones.
Androgens are involved in the formation and support of sexual desire, stimulates hair growth in the dependent zones, stimulate the process of forming part of the secondary sexual characteristics. The maximum concentration of androgens falls on the pubertal period - from 8 to 14 years.
Adrenal glands are an extremely important part of the endocrine system. The organs produce more than 40 different hormones that regulate carbohydrate, lipid, protein metabolism and are involved in a variety of reactions.
Hormones secreted by the adrenal cortex: