Explain the following Human Endocrine Glands – Pancreas (Islets of Langerhans), Adrenal gland (Adrenal cortex and Adrenal medulla) andThymus gland

Pancreas (Islets of Langerhans)

  • The pancreas is an elongated, yellowish gland situated in the loop of the stomach and duodenum. It is exocrine and endocrine in nature. 
  • The exocrine pancreas secretes pancreatic juice which plays a role in digestion while, the endocrine portion is made up of Islets of Langerhans.
  • The Islets of Langerhans consist of two types of cells namely alpha cells and beta cells. 
  • The alpha cells secrete glucagon and the beta cells secrete insulin.

Functions of Pancreatic hormones

  • A balance between insulin and glucagon production is necessary to maintain blood glucose concentration.


  • Insulin helps in the conversion of glucose into glycogen which is stored in the liver and skeletal muscles.
  • It promotes the transport of glucose into the cells.
  • It decreases the concentration of glucose in the blood.


  • Glucagon helps in the breakdown of glycogen to glucose in the liver.
  • It increases blood glucose levels.

Diabetes mellitus

  • The deficiency of insulin causes Diabetes mellitus. 

It is characterized by 

  • Increase in blood sugar level (Hyperglycemia).
  • Excretion of excess glucose in the urine (Glycosuria).
  • Frequent urination (Polyuria).
  • Increased thirst (Polydipsia).
  • Increase in appetite (Polyphagia).

Adrenal Gland

  • The adrenal glands are located above each kidney. They are also called supra renal glands.
  • The outer part is the adrenal cortex and the inner part is the adrenal medulla. The two distinct parts are structurally and functionally different.

Adrenal Cortex

  • The adrenal cortex consists of three layers of cells. They are zona glomerulosa, zona fasciculata and zona reticularis

Hormones of Adrenal Cortex

  • The hormones secreted by the adrenal cortex are corticosteroids. They are classified into
  • Glucocorticoids
  • Mineralocorticoids

Functions of adrenocortical hormones


  • The glucocorticoids secreted by the zona fasciculata are cortisol and corticosterone
  • They regulate cell metabolism.
  • It stimulates the formation of glucose from glycogen in the liver.
  • It is an anti-inflammatory and anti-allergic agent.


  • The mineralocorticoids secreted by zona glomerulosa is aldosterone
  • It helps to reabsorb sodium ions from the renal tubules.
  • It causes increased excretion of potassium ions.
  • It regulates electrolyte balance, body fluid volume, osmotic pressure and blood pressure.

Adrenal Medulla

  • The adrenal medulla is composed of chromaffin cells. They are richly supplied with sympathetic and parasympathetic nerves.

Hormones of Adrenal Medulla

  • It secretes two hormones namely
  • Epinephrine (Adrenaline) 
  • Norepinephrine (Noradrenaline)
  • They are together called as “Emergency hormones”. It is produced during conditions of stress and emotion. Hence it is also referred as the “flight, fright and fight hormone”.

Functions of adrenal medullary hormones

Epinephrine (Adrenaline)

  • It promotes the conversion of glycogen to glucose in the liver and muscles.
  • It increases heartbeat and blood pressure.
  • It increases the rate of respiration by dilation of bronchi and trachea.
  • It causes dilation of the pupil in the eye. 
  • It decreases blood flow through the skin.

Norepinephrine (Noradrenalin) 

  • Most of its actions are similar to those of epinephrine.
error: Content is protected !!
Open chat
Hello Exam Machine Team. I Would Like To Join TNPSC Group 2 Mains Test Batch.