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.
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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:
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:
MineralocorticoidsMineralocorticoids 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:
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:
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:
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.
Hakimuddin Kuwakhedawala is based in India with over 15 years experience as a teacher. Teaching and writing are his passion. Most of the articles of Hakimuddin are related to education, exam, environmental problems, etc.
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