Saturday, 7 February 2015

write a short note on ENDOCRINE SYSTEM

The glands in the human body are of two types:

1.exocrine glands
2. endocrine glands

       The exocrine glands produce fluid secretions that delivered by tube of ducts either to the body surface e.g. glands of skin or to the inner regions where these are required e.g. pancreas delivers its pancreatic juice to the intestine for digesting food etc.

        Endocrine glands produce secretions called hormones that are not carried by ducts but are passed into the blood stream and carried to the target area by blood circulation. The following endocrine glands are present in the human body.

1. Pituitary gland                                    4. pancreas (islets of langerhans)
3. Thyroid gland                                     5. Adrenal glands
3. Parathyroid glands                              6. Gonads

        The function of endocrine glands is very much inter-related. Several of the hormones produced by them serve only to alter the functions of other endocrine glands. The serve as double check atomic control over one another.

1. Pituitary gland
     The pituitary gland is know as the master gland in the body and plays and important role in several ways. It has certain hormones which have direct action on the body e.g. the growth hormone.

    In addition it has hormones which control the action of the another endocrine glands. It is closely associated with the base of brain in the skull. In size it is a little larger than a garden pea. There are two lobes of pituitary gland each produces its own hormones.

         3.          Anterior lobe                2.             posterior lobe
            Anterior lobe produce many hormones. One of the important hormones produced by the pituitary is somatotrophic (STH) which is the growth promoting hormones due to which the process of growth takes place in the body. It influences all those organs and tissues of the concerned in the process of growth.

              Another important hormone is called thyroid stimulating hormone (TSH) which stimulates the thyroid to produce its hormone. The remaining hormones of the anterior lobe of pituitary influence the activities of reproductive organs both in men and women but in different ways and control the working of adrenal glands.

               Two hormones are produced by the posterior lobe of pituitary gland. One hormone helps to conserve water in the body according to requirement, and the other has no effect on males but has certain effect in females.

Thyroid gland.
the thyroid gland is located in the neck and fits closely around the from and side of trachea (wind  pipe) just below the organ of voice of larynx. The thyroid receives a lot of blood supply to nourish its cells and to carry away the hormones it produces. It produce two hormones.

         1.   Thyroxin                   2.     Calcitonin.
The above hormones of thyroid are produced under the influence of TSH from the pituitary gland. The thyroid hormones increase the consumption of oxygen by the body tissues. This increase this increase the rate of metabolism. They also increase the ability of a person to think. Adequate supply of these hormones is also needed for normal growth and skeletal development in children.

Parathyroid gland.
These are very small structures usually four in number embedded in the back side of the thyroid gland. They produce parathyroid hormone which control the amount of calcium and phosphate in the blood serum.
   
Pancreas.
Pancreas is present in the abdominal cavity close to the stomach. Pancreas is know as double gland as it has two kinds of glandular tissues. One exocrine and the other endocrine in function. The main bulk of pancreas is exocrine that produce pancreatic juice which helps in the digestion and carried by the pancreatic duct to the intestine. Distributed at various places in its tissue are groups of cells, known as islets of langerhans  which are endocrine (not having ducts). The islets of langerhans produce two hormone:

           1.      Insulin                    2.     Glucagon

   These two hormones have opposite effect in regulating use of glucose in the body. The two hormones therefore counter balance each other. When the amount of glucose in the blood plasma increase the production of insulin is also increased due to which the entry of glucose into muscles and other tissue from the blood is made easier. In the absence of insulin the glucose level in the blood is raised resulting in the disease known as diabetes mellitus.

   Too much insulin in the blood may cause lowering of glucose level to such an extent that a may result in unconsciousness and death. Glucagon, the second hormone in such emergency situations brings about release of stored blood sugar so as to maintain a proper level of glucose in the blood,

Adrenal glands
Adrenal glands are paired and lie in abdominal cavity above the kidneys. Adrenal glands produce adrenaline which prepares the body for action in an emergency by raising blood pressure, increasing heart and breathing rate.

Gonads
Male gonads or testes
They have two functions, to produce male sex-cells (sperms) and to produce the male hormones androgens e.g. testosterone. These are produced by the interstitial cells of testes. Testosterone helps in the development of male secondary sex characters such as growth of hair on the face and thickness or coarseness of voice in males.

Female gonads or ovaries
Ovaries in the female produce oestrogen which controls development of secondary sexual characters (development of breast etc.) and causes the lining of uterus of thicken.



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