Information about adrenal gland and its functions


Do you know which gland is known as an emergency gland and which hormone is known as the emergency hormone? In this article, you will find a detailed explanation of the adrenal gland which is also known as the emergency gland. To know about the hormones, please read this article.

Structure

The adrenal gland is derived from mesoderm of the embryo and it is also known as suprarenal gland. In man and other mammals, the adrenal gland is located on the dorsal side of the kidney as cap-like structure. The outer part of the adrenal gland is formed from mesoderm, whereas inner part by neural ectoderm. Each gland measures 1 to 2 inches in length and weighs about 8-9 grams. Adrenal glands were first described by Eustachius in 1563. The adrenal gland is made up of the upper cortex and inner medulla. Cortex is derived from mesoderm while medulla from ectoderm or neural crest. Suprarenal glands are richly vascularized. These glands are smaller in female than male. Adrenal cortex and adrenal medulla secrete independent hormone.

adrenal gland
(Image curtsey: wikipedia.org)

Hormones of Adrenal cortex

The adrenal cortex is the peripheral part and constitutes about 90% of the adrenal gland. The adrenal cortex is made up of three layers:
  • Outer thin layer (Zona glomerulosa)
  • Middle thick layer (Zona fasciculata)
  • Internal layer (Zona reticularis)


More than 40 steroid hormones are secreted by the adrenal cortex. These hormones are collectively called as adrenocorticosteriod. All of them are fat-soluble steroids. These hormones fall under the following four categories:
  1. Mineralocorticoids
  2. Glucocorticoids
  3. Sex hormones
  4. Mineralocorticoids

Mineralocorticoids

Mineralocorticoids hormone is a powerful salt-retaining steroid of the adrenal cortex. This hormone causes retention of sodium and increases urinary excretion of potassium. The hyposecretion of cortex or removal of this part of gland causes the imbalance of sodium and potassium which leads to nervous disorders and convulsions. Without mineralocorticoids persons soon develop the diminished cardiac output which proceeds to a shock like a state followed by death. This can be prevented by the administration of aldosterone or some other mineralocorticoid i.e. mineralocorticoids are called life-saving hormones.

Glucocorticoids

There are two important glucocorticoids:
  1. Cortisol or Hydrocortisone : Cortisol affects the fat metabolism in our body.
  2. Corticosterone : Corticosterone controls the carbohydrate metabolism. Conversion of excess glucose into glycogen is regulated by this hormone. Corticosterone also helps in maintaining the concentration and distribution of electrolytes, balance of water and salts in our body. The secretion of adrenocorticotropic hormone (ACTH) by adrenal cortex is under the direct control of pituitary gland . If the adrenal cortex is removed from a person, the whole metabolism is disturbed. It results in Addison's disease. Untimely sexual maturity is achieved. Not only that, the sex of a person can also be reversed by administration of hormone of opposite sex.

Sex Hormones

There are two sex hormones Androgen (male sex hormone) and Estrogen (female sex hormones). These male and female sex hormones produce nearly the same effect on the body as those produced by the sex glands. Excessive production of these hormones in young children would bring premature sexual maturity. If the male hormone is secreted in a female, she develops secondary sexual characters of the male. Excess secretion of sex hormones may lead to abnormal body growth. For example, a five-year-old baby girl gave birth to a child in Peru. This was the result of excessive secretion of the female hormone in our body.

Cortisone

Cortisone affects the protein metabolism and is useful in the treatment of certain type of arthritis.

Hyposecretion of Adrenal Cortex

Low production or hyposecretion of glucocorticoids causes Addison's disease characterized by shock, reduced blood pressure high urea level in blood and rise in normal body temperature. The skin of the hands, neck and face is bronzed due to melanin. The sensitivity of the body to temperature cold is increased and finally, the organism becomes dead.

Hypersecretion of Adrenal Cortex

The hypersecretion of adrenal cortex may cause the following diseases:
  • Cushing's syndrome : Overproduction or hypersecretion of glucocorticoids causes Cushing's syndrome with excessive fat deposition. Cushing's disease can be characterized by hyperglycemia, increased protein catabolism, muscle weakness, disorders of the skin and bones, hypertension, diabetes, mellitus, etc.
  • Adrenal virilism : Overproduction of the glucocorticoids causes adrenal virilism or adrenogenital syndrome. Symptoms of this disease in adults are the reversal of ex-characters. Females tend to change into males. Their face, body appearance, voice, etc become the male type. Beard and moustache grow, menstruations stops, uterus and ovaries degenerate, clitoris enlarges. However, in male feminisation occurs but it is rare.
  • Aldosteronism or Conn's syndrome : Aldosteronism is caused due to excessive secretion of aldosterone from adrenal cortical tumor. It results in the increase of sodium ions concentration and the decrease in the potassium ion concentration in the plasma, resulting in the increase of blood pressure. Prolonged loss of potassium ion damages kidneys resulting in polyuria.


Hormones of adrenal medulla

The adrenal medulla consists of chromaffin cells which are surrounded by venous sinuses into which hormones are released. Adrenal medulla forms remaining 10% of the adrenal gland. Adrenal medulla develops from the neural part in embryonic stage. The adrenal medulla is regulated by the autonomic nervous system. The following two hormones are secreted by chromaffin cells of adrenal medulla:
  1. Adrenalin or epinephrine
  2. Noradrenalin


Adrenalin or Epinephrine

Adrenalin hormone is a derivative of tyrosine. Chromaffin cells secrete about 80% adrenalin hormone. Adrenalin hormone affects all the organs affected by the autonomous nervous system. Adrenalin hormone is also known as emergency hormone as it is used as heart stimulant in acute emergencies. Adrenalin is secreted in proportional to the stimulus through the central nervous system. Under the condition of stimuli such as cold, heat, drugs and emotional excitement, the secretion of adrenalin is greatly increased. In circumstances of great stress-strain, fear and emotional upheaval, the body required additional energy in hurry. Adrenalin accordingly increases the conversion of glycogen to glucose and thus provides quickly available energy. As adrenalin also increases blood flow, the available glucose may quickly go where it is needed. Adrenalin dilates the blood vessels in the heart and skeletal muscles, thus decreasing the peripheral resistance and permitting a copious flow of blood to meet the needs of fight and flight. The complete removal of adrenal causes death within a fortnight.

Noradrenalin or Norepinephrine

Noradrenalin is also secreted by chromaffin cells. Noradrenalin is the tonus hormone for the circulatory system. Noradrenalin has little activity in regulating carbohydrate metabolism and is not a vasodilator; it is a powerful excitor. It has constrictor effect, causes the greater rise in blood pressure than adrenalin. It raises both systolic and a diastolic pressure. The main function of noradrenaline is the normal control of blood circulation. It is much related with fear, pain, anger, etc. Its action is opposite to adrenalin.

Conclusion

Now you would be able to understand the different hormones secreted by the adrenal gland and their functions.


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