Adrenal Glands – Class 11 | Chapter – 22 | Biology Short Notes Series PDF

Adrenal glands are triangular-shaped endocrine glands. These glands produce hormones which help in regulating metabolism and blood pressure, functioning of the immune system and adrenaline rush. Adrenal gland secrete important hormones like Epinephrine, Nor-epinephrine, Hydrocortisone, Corticosterone. Adrenal glands are also considered as “Glands of Emergency” as these produce most of the vital hormones needed in the emergency conditions. These glands are located extra-peritoneally at the upper pole of each of the kidneys. Hence, these are also called “Suprarenal Glands.”

Location of Adrenal Glands

Human body has two adrenal gland, above each of the kidneys. Even the name “adrenal” suggests its location ( ad- near & renes- kidneys). On the front of the left adrenal gland lies stomachpancreas and spleen and on the back lies left crus of the diaphragm. The right adrenal gland is surrounded by inferior vena cava and the right lobe of the liver is situated in the front and right crus of the diaphragm lies in the back. The below diagram shows the location of the adrenal glands: 

Adrenal Gland Location

Anatomy of Adrenal Glands

The two adrenal glands have different shapes. The right gland is in the shape of a pyramid while the left gland is semilunar. The left adrenal gland is also larger than the right one. Adrenal glands are approximately 10 centimeter cube in volume with a height of 5 centimeter and breadth of 3 cm. It is proven that healthy glands are yellowish. Adrenal glands are ductless glands which release the hormones directly into the blood or lymph system. Thus, it gets circulated to the whole body.

Anatomy of Adrenal Glands

Adrenal Capsule

The capsule is made of fat and is the outermost layer of the adrenal glands. Capsule acts as a protective layer. It’s function is to enclose the adrenal glands and protect the glands.

Adrenal Cortex

The adrenal cortex is a three-layered outermost part of the adrenal glands. Its main purpose is to produce hormones such as aldosterone, cortisol, and androgens. Each of the three layers of the cortex are called zones. It is easy to differentiate the layers by studying them under a microscope.

  • Zona Glomerulosa – It secretes mainly aldosterone which helps in absorption of sodium by the kidneys. This further maintains the balance of water and salt in the body.
  • Zona Fasciculata – It produces cortisol which is a very important hormone for maintaining blood sugar levels and generating certain substances which help in repairing damaged tissues. It also secretes small quantities of androgens (hormones which plays a vital role in development of sexual traits and reproduction) like testosterone & aldosterone.
  • Zona Reticularis – It produces DHEA or dehydroepiandrosterone which is a hormone that helps in producing other hormones such as testosterone and estrogen, and etc. DHEA is maximum at adulthood which starts from 21 or 22 years of age.

Adrenal Medulla

It is the innermost part of the adrenal gland. It has the Chromaffin cells in it, which are the main source of catecholamines and endorphins. Catecholamines help in managing stress and endorphins are such hormones which are produced when we exercise and help in relieving pain and tension and boosts our happiness.

Functions of Adrenal Glands

Adrenal Gland are responsible for the secretion of important hormones like Glucocorticoids, Mineralocorticoids, Adrenal sex steroids, Catecholamines. These glands play crucial bodily functions through the regulation of certain hormones. The major roles of adrenal glands are mentioned below- 

  • The most well-known job done by adrenal glands is triggering a “fight or flight” response. It releases the stress hormone which triggers this response.
  • Some crucial hormones like cortisol are known for its anti-inflammatory actions and immune response are also released by the adrenal glands
  • Adrenal gland also balance the salt and water in the body by releasing hormones like aldosterone.

Disorders of Adrenal Glands

Adrenal Gland disorders happen when not the right amount of hormones are produced by the adrenal glands. This can also be due to some abnormal growths or a tumour.

Conditions related to uneven hormone production

  • Cushing’s Syndrome is when the adrenal gland produce a large amount of cortisol. This term is also referred to when a medical patient is given high steroids for the treatment purposes.
  • Congenital Adrenal Hyperplasia (CAH) happens when the body produces very low levels of cortisol genetically. Depending on the intensity of this disorder, high levels of male hormone is produced.
  • Addison’s Disease may happen when not enough cortisol or aldosterone is made. It may raise symptoms like weakness, fatigue, low blood pressure, nausea, etc.

Conditions related to abnormal growth and tumour

  • Adrenocortical carcinoma is a rare condition that refers to cancer forming in the outer layer of the adrenal gland.
  • Pheochromocytoma is a condition when a non-cancerous (benign) tumor develops in an adrenal gland. Too much epinephrine and norepinephrine is produced during this condition which in turn raises the blood pressure.

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By Team Learning Mantras