A gland is a collection of cells which creates a useful chemical for the body in its various reactions. Two kinds of glands are seen in the human body:
1. Exocrine glands – e.g. Liver, Spleen, Pancreas. Their secretions are taken to the desired part by a special channel called duct.
2. Endocrine or Ductless glands – e.g. Pituitary (The Master Gland), Suprarenal, Thyroid. Their secretions are transported by blood to the desired body part.
The largest gland in the body, the liver is a reddish-brown organ about 85 gm. The liver performs the following functions:
1. Storage of excess sugar as glycogen (insoluble carbohydrate), which helps fat digestion.
2. Manufacture of urine which is filtered from blood by kidneys.
3. Manufacture of Vitamin A from Pro-carotene.
4. Destruction of poisonous substances in the body.
The pancreas secretes a clear, colourless juice with important digestive properties. It is the only gland in the body to have an exocrine and an endocrine character. As an exocrine gland, it secretes pancreatic juice which, through the pancreatic duct, goes to the duodenum to help digestion there. As an endocrine gland, it secretes insulin which helps utilize sugar in the body. Insulin is secreted by special pancreatic cells called Islets of Langerhans. The deficiency of insulin causes diabetes, a disease in which the patient passes sugar in urine. The disease is cured by insulin injections invented by F. Banting.
Bluish-red organ to the left of the stomach. The white blood corpuscles are formed here, and the worn out red blood corpuscles are disposed of in the spleen pulp.
It is a reddish-grey gland hanging from the lower surface of the brain. Its secretion regulates growth and height, milk secretion in mammals, and influences sex organs.
The pituitary gland secretes hormones which mainatin homeostasis (stable internal environment) including trophic hormones that stimulate other endocrine glands. The Pituitary is also called the Master Gland because of its homeostatic role and its ability to influence other glands.
They are small, yellowish glands just above the kidneys, one on each side. Their secretion is known as adrenaline and noradrenaline. This secretion is released in emergencies i.e Fight or Flight Response and prepares the body for such situations by releasing excess energy.
A brownish-red body located in front of the neck. An abnormal increase in its size is called goitre. Its secretion, known as thyroxine, is rich in iodine