Adrenal Gland. There is a pair of adrenal glands located one just above each kidney. So, it is also called suprarenal gland.

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1 Adrenal Gland There is a pair of adrenal glands located one just above each kidney. So, it is also called suprarenal gland. Origin: - It is dual in origin i.e. its outer part or, adrenal cortex originates from mesoderm whereas its inner part or adrenal medulla originates from ectoderm. [Adrenal cortex is essential for life but adrenal medulla is not.] Structure, Size & Weight: - Each adrenal gland in man weight about 6 gm, measures 25 to 50 mm in length. It is somewhat pyramidal in shape and has a rich blood supply. Each gland consists of two parts that are embryologically, anatomically and functionally different. An external reddish brown cortex which surrounds an internal grayish medulla.

2 Anatomy: - On the basis of histology adrenal cortex is differentiated into three zones: -

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4 1. Zona-glomerulosa: - It is the outermost zone of adrenal cortex. It consists of densely packed 5 or 6 layers of cells. 2. Zona-fasciculata: - It is middle zone and consists of rows or chords of cholesterol rich cells. It is the thickest layer.

5 3. Zona-reticularis: - It is the innermost zone or zone adjacent to medulla. It has a net like structure. Cells of adrenal gland are rich in cholesterol and ascorbic acid. Current trend is to divide the adrenal glands on two zones only on the basis of function or physiology: - 1. Zona-glomerulosa: - It is not under the control of ACTH. It mostly secretess aldosterone. 2. Zona-Fasciculata-reticularis: - It is under the control of ACTH. It secretes mostly cortisol by fasciculate and weak androgens by reticularis. Hormones of Adrenal Cortex: - (i) Glucocorticoids: - It is mostly secreted by zona-fasciculata. Functions: - It increases the blood glucose level at the expense of liver glycogen and enhance the conversion of protein and fat to carbohydrate. In case of bleeding, it constricts blood vessels to offset the drop in blood pressure due to blood loss. It has anti-inglammatory and anti-allergic effects. (ii) Mineralocorticoids: - It is mostly secreted by zona-glomerulosa. Functions: - It regulates the metabolism of Na nr~ & K nr~.

6 It tends to increase the reabsorption of Na nr~ from urine, saliva, bile and sweat to reduce its loss from the body. It also increases the elimination of K nr~. It increases reabsorption of water from the urine. Reabsorption of water increases the volume of blood. (iii) Sexocorticoid: - It is mostly secreted from both the zona-fasciculata-reticularis. Its effect is similar to male sex hormone. E.g. adrenal cortical tumours in females may give rise to masculine characters. Such as beard and deep voice etc. although, the female sex hormones have also been detected. Hormones of Adrenal Medulla: - The adrenal medulla consists of two distinct types of cells. These are adrenaline secreting cells and the nor-adrenaline secreting cells which are responsible for the production of the two hormones adrenaline or epinephrine and nor-adrenaline or nor-epinephrine in the ration of 4:1. These hormones are secreted in response to sympathetic stimulation. Adrenaline or Epinephrine: - It is formed from the amino acid tyrosine. Functions: - Contraction of smalll arteries of skin and viscera to divent blood to muscles. Dilation of pupila. Heart beat is increased.

7 It also stimulates the breakdown of liver and muscle glycogen to produce glucose for repiratory. It helps in more oxygen consumption by relaxation of trachea and bronchus. Faster coagulation of blood. Nor-adrenaline or Nor-epinephrine: - Its influence on heart is lesser than adrenaline It also increases the rate of other metabolic activities such as glycogenolysis in the liver and muscle and glucose released into the blood. Note: - Adrenaline and nor-adrenaline differ in their effects on blood vessels. Nor-adrenaline causes vasoconstriction of all blood vessels whereas adrenaline causes vasoconstriction of blood vessels of skin and gut and vasodilation of blood vesselss to muscles and brain. Its secretion is increased in emergency case such as stress, fear, anger, shock etc. All these conditions require more energy which is supplied by increasing heart beat, level of glucose etc. So, it is also called emergency hormone and adrenal gland is called glands of emergency. Disorder of Adrenal Gland: - (i) Addison s disease: - It is caused by hyposecretion of mineralocorticoids. [This disease was first described by Thomas Addison, Father of Endocrinology, 1855] Lowering of blood pressure, body temperature and BMR (Basic Metabolic Rate). Muscular weakness.

8 Ion imbalance which lowers water retention. Hypoglycemia, vomiting. Loss of appetite. Excessive loss of Na nr~, Cl in the urine. Brownish pigmentation or Bronzing of the skin especially the exposed parts e.g. the face and hands due to deposition of melanin. Cushing s Disease: - It is restricted to those cases which are of pituitary origin. Cushing s Syndrome: - Originates from adrenal glands. It is caused by hypersecretion of glucocoticoids. High blood pressure. High blood sugar level. Excretion of sugar in urine. Rise in blood volume and blood pressure. High Na nr~ concentration in plasma and low K nr~ concentration in plasma. Adrenal Virilism: - It is caused by excess of sexocorticoids in a female. She develops male secondary sexual characters such as beard, moustaches and hoarse voice. Gynecomastia: - It is caused by excess of sexocorticoids in male. Secondary sexual characters appears early. Sometimes n male, there is overgrowth of mammary glands.