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Renin Angiotensin Mechanism.

Adrenal Gland.

 

Introduction:

  • Also called “Suprarenal Gland”.

  • Adrenal glands receive one of the highest rates of blood flow in the body.

  • They secrete many essential hormones.

Location:

  • Adrenal gland consists of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule.

  • As they are present on top of the kidney they are called “Suprarenal Glands”.

Structure:

  • Each adrenal gland is 3-5 cm in height, 2-3 cm in width and about 1 cm thick with a weight of 3.5-5 gm.

  • Each gland consists of two parts.

    • Adrenal cortex – the outer part

    • Adrenal medulla – the inner part

Adrenal cortex:

  • The adrenal cortex is divided into three zones. 

  • Each zone secretes different hormones,

    • Zona glomerulosa – the outer zone secretes mineralocorticoids.

    • Zona fasciculata – the middle zone secrets glucocorticoids.

    • Zona reticularis – the inner zone secretes androgens.

Mineralocorticoids:

  • The major mineralocorticoid is aldosterone. 

  • It maintains water and electrolyte balance in the body.

  • It is secreted in response to ,

    • Low Sodium levels.

    • Low blood volume.

    • Low blood pressure.

    • High Potassium levels.

  • Once secreted,

    • Increases Potassium secretion.

    • Causes Sodium and water retention.

    • Corrects blood volume and blood pressure.

Glucocorticoids:

  • Important glucocorticoids are,

    • Cortisol (Hydrocortisone), 

    • Corticosterone and 

    • Cortisone.

  • They have a powerful effect on metabolism.

  • Cortisol is the most active Glucocorticoid, released by the body to handle the stress, hence called “stress hormone”.

  • They possess powerful “Anti-inflammatory action.

  • In high doses they cause depression of immunity.

Androgens:

  • They are steroidal sex hormones produced by Zona reticularis the deepest are of the adrenal cortex.

  • Their amount is very small hence the effect is very minimal.

  • Sex hormones are secreted by gonads on puberty in large quantities.

  • In tissues they get converted to testosterone and estrogen.

Adrenal medulla:

  • Adrenal medulla is a part of the sympathetic nervous system and releases hormones namely adrenaline and noradrenaline.

  • These hormones increase activity of the heart, blood pressure and metabolism.

Disorders of Adrenal Gland:

  1. Cushing’s Syndrome:

  • It is caused due to a pituitary tumor causing increased secretion of ACTH which results in high blood levels of cortisol.

  • It is characterized by abnormally high blood glucose levels and accumulation of lipids on the face and neck causing “moon face”.

  • It leads to type II diabetes, weight gain, hair loss, decreased immunity.

  1.  Addison’s disease:

  • It is a rare disorder.

  • Caused due to hypo secretion of corticosteroids by Adrenal glands.

  • It results in increased potassium and decreased sodium level in blood, low blood pressure, dehydration, weight loss, muscular weakness, decreased cardiac output.

Commonly Asked Questions:

  1. Write in detail about Suprarenal Glands.

  2. Write a short note on hormones of adrenal gland.

  3. Discuss in short disorders of adrenal gland.
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