Pancreas

Pancreas is a mixed gland as it performs both endocrine and exocrine functions. Pancreas is an elongated, yellowish gland. It consists of lobules that secrete pancreatic juice. Interspersed at random among the lobules are Islets of langerhans, which produce hormones.

Hormones

The Islands of langerhans secrete four hormones insulin, glucagon, somatostatin and pancreatic polypetide. Insulin and glucagon have antagonistic effects on the blood glucose level.

Insulin

They are secreted by the betacells of the Islets of langerhans

Its secretion is stimulated by the rise in blood-glucose level, such as after a meal. It has many functions such as

i) It enables the liver and muscles to store glucose as glycogen and enables the tissues to take up and use glucose as a source of energy.

This lowers the blood-glucose level.

ii) It promotes synthesis of proteins from amino acids in the tissues.

iii) It reduces breakdown of proteins to maintain the tissues.

iv) It reduces respiratory breakdown of fats in the body.

Deficiency of insulin causes Diabetes mellitus. The patient cannot use or store glucose. Thus glucose accumulates in the blood and is also excreted along with urine. Degradation of fats increases producing ketone bodies such as acetoacetate and acetone. Blood cholesterol rises, healing power is impaired so that injuries may change into gangrenes. The diabetic person has blurred vision and is weak, tired, irritable, nauseated and underweight. Administration of insulin gives relief by lowering blood-glucose level.

Distinguish between Diabetes mellitus and Diabetes insipidus:

Distinguish between Hyperglycaemia and Hypoglycaemia:

Glucogon

It is secreted in response to a fall in the blood glucose level by the alphacell of the Islets of langerhans Its action is opposite to that of insulin. It brings about change of liver glycogen to blood glucose, to provide energy between meals.

Somatostatin

It is secreted by the delta cells of the islets of langerhans. It decreases the rate of nutrient absorption into the blood stream from the gastrointestinal tract and inhibits the secretion of insulin and glucagon.

Pancreatic poly peptide

It inhibits the release of pancreatic juice.

Pineal Gland

The endocrine gland attached to the roof of third ventricle in the rear portion of brain, is known as the pineal gland, named for its resemblance to a pine cone. It has no direct connection with central nervous system. It is variable in size and weighs about 150 mg, but it is richly vascularised and secretes several hormones, including melatonin. In humans, it has no lightsensitive cells, like lower vertebrates, where pineal is eye-like and responds to light. Pineal gland functions as a biological clock and a neurosecretory transducer, converting neural information. More melatonin is produced during darkness. Its formation is interrupted when light enters the eyes and stimulates the retinal neurons. They transmit impulses to the hypothalamus, and finally to the pineal gland. The result is inhibition of melatonin secretion. In this way, the release of melatonin is governed by the diurnal darkness cycle.