Important Endocrine Glands
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| Important Endocrine Glands |
1 Pituitary Gland
It is a pea shaped gland attached to the hypothalamus of brain. Many hormones of pituitary gland influence the secretions of other endocrine glands. However some hormones of this gland act directly on various tissues of body. There are two lobe sof pituitary gland anterior lobe and posterior lobe.
a. Anterior Lobe
It produces many hormones. One of its important hormones is somatotrophin. It promotes the growth of body. If the production of this hormone is diminished during growing age the rate of growth decreases. This condition is called dawrfism. If this hormone is excessively produced during growing age its leads to gigantism. If somatotrophin is excessively produced after growing age internal organs and body extremities alone grow large. This condition is known as acromegaly. Such persons will have large hands feet and jawbones.
Another hormone secreted by the anterior lobe of pituitary gland is thyroid stimulating hormone. It stimulates thyroid gland to secrete its hormones. The remaining hormones of anterior lobe influence reproductive organs and also control adrenal glands.
b. posterior Lobe
The posterior lobe of pituitary gland store and secretes two hormones oxytocin and vasopressin. These hormone are produced by hypothalamus.
Vasopressin increases the rate of reabsorption of water from nephrons. When we have low amount of water in body fluids pituitary gland secretes vasopressin and so more reabsorption of water occurs from nephrons into blood. In this way body retains water and less amount of urine is produced. On the other hand when body fluids have more then normal water there is a decline in the required amount less water is reabsorbed from nephrons and there is excessive loss of water through urine. This condition is known as diabetes insipidus.
2 Thyroid gland
This is the largest endocrine gland in the human body. It is present in neck region below larynx and produces a hormone thyroxin. Lodine is required for the production of this hormone. If a person lacks iodine in diet thyroid gland enlarges. This disorder is called goitre.
Thyroxin increases the break down of food and releases of energy in body. It is also responsible for the growth of body. Hypothyroidism is caused by under production of thyroxin. It is characterized by low energy production in body and slowing down of heart beat. Hyperthyroidism is caused by over production of thyroxin. Its symptoms are increase in energy production increased heart beat frequent sweating and shivering of hands.
The thyroid gland produces another hormone called calcitonin. It decreases the level of calcium ions in blood and promotes the absorption of calcium from blood into bones.
3 Parathyroid Glands
These are four glands situated on the posterior side of thyroid gland. They produce a hormone known as parathormone. It increases the level of calcium ions in blood. When there is increased production of parathormone more than normal calcium salts are absorbed from the bones and added to blood. Consequently the bones become brittle. If there is deficiency in the production of parathormone blood calcium leve falls. It leads to tetany which affects the functioning of muscles.
4 Adrenal Glands
Two adrenal glands are situated above kidneys. Each adrenal glands consist of two parts. The outer part is cortex and the inner part is medulla. Adrenal medulla secretes a hormone called epinephrine or adernaline in response to stress. It prepares our body to overcome emergency situations. Therefore adrenaline is also termed as emergency hormone.
The adrenal cortex secretes many hormones called corticosteroids which maintain the balance of salts and water in blood.
5 Pancreas
This organ has two functions the major part of pancreas is a ducted gland. This portion secretes digestive enzymes through a duct into small intestine. Some portions of pancreas serve as ductless gland. This portion contains groups of endocrine cells referred to as islets of langerhans. These islets secrete two hormones insulin and glucagon. Glucagon influences the liver to release glucose in blood and so the blood glucose concentration rises. Insulin influences the liver to take excess glucose from blood and so the blood glucose concentration falls.
If a person pancreas dose not make normal quantity of insulin the blood glucose concentration rises and we say that the person has diabetes mellitus . Persons with diabetes have loss of body weight weakening of muscles and tiredness.The disease can be controlled by insulin administration. Formerly insulin extracted from animals was used for this purpose. But now human insulin produced from bacteria through genetic engineering is available.
6 Gonads
Testes and ovaries are the male and female reproductive organs gonads. In addition to producing gametes gonads also secrete hormones called sex.hormones. Testes secrete hormones testosterone which is responsible for the development of male secondary sex characters such as growth of hair on face and coarseness of voice etc.
Ovaries secrete estrogen and progesterone which are responsible for the development of female secondary characters such as the development of breast etc.
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