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.

• 

2.  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.