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Human Endocrine Glands

                             Human Endocrine Glands

Pituitary gland:- It is a small gland attached to ventral side of the brain. Its most import as it secretes a number of hormones that regulates different parts of the body. It also controls the functions of other endocrine gland.  It has mainly two parts: - anterior lobe and posterior lobe. Anterior lobe secrete many hormones, one of these is growth hormone, which regulates growth and development of the body. It promotes bone and muscles, when body is growing. Excessive secretion of this hormone leads to gigantism, abnormal condition of excessive growth.  Insufficient secretion of this hormone in childhood leading to dwarfism, an abnormal condition of stunted growth. The posterior lobe secretes two hormones. One of these helps in childbirth and another influence the reabsorption of water in the kidney. 

 Pineal gland:- It is a small gland attached to ventral side of the brain. It has light-sensitive cells. It controls biological clock. 

 Thyroid gland:- It is large gland located behind the larynx in the neck. It secrete thyroxine hormone, which control metabolism of carbohydrate, protein and fat and brings about balanced growth.  excesses secretion of thyroxin is called hyperthyroidism. Which increases metabolic activities, results in the fat stored is depleted and loss of body weight. Insufficient secretion of thyroxine is called hypothyroidism, which lowers the general metabolism, results in increases body weight. Excessive secretion of thyroxine result thyroid gland became enlarged means the neck swells up and eyeball bulge outward. This is called exophthalmic goitre. The goitre caused by less iodine inn diet is called simple goitre. Iodine is needed for synthesis of thyroxine.   

 Parathyroid gland:- These are two pairs of small gland buried in thyroid gland. It secretes parathormone, which increases calcium level of blood by taking out calcium from bone. A certain amount of calcium in blood is essential for functions such as muscular activity and blood clotting. 

 Thymus gland:- This gland located near the heart and s present in new born baby. It became smaller with age and lost in adults. This produces WBC, which fight against infection. 

 Islets of Langerhans:- Pancreas is a digestive gland lie in the C-shaped bend of the duodenum. Inside pancreas there are groups of hormone secreting cells. These groups are called islets of Langerhans. Among these hormones produced by them insulin is the most important hormone. It controls the rate of oxidation of glucose. It helps liver and muscles cells to absorb sugar from the blood. It also controls the formation of glycogen from glucose in the liver.  People who unable to secrete sufficient insulin suffer from a condition called diabetes mellitus.  

 Adrenal glands:- These are two glands one on each kidney. These glands secrete adrenaline or epinephrine. This secretes when the individual is under great physical or emotional stress or feels threatened by any kind of danger. Adrenaline increases the heartbeat, respiration rate and blood pressure. Adrenaline constricts all blood vessels except those that supply blood to the heart muscles and skeletal muscles. More air is inhaled. As the small arteries around digestive organ constricted, blood diverted to skeletal muscles to carry out response.    Adrenaline is called fight and flight hormone because there is a surge of adrenaline when a person is fight or preparing to fight or running away from danger. The changes caused by adrenaline prepare the body to react during emergency. Hence, adrenaline is also called emergency hormone.  

 Testis:- The main function of testis is to produce sperm. It also synthesizes testosterone, a male sex hormone. Its secretion begins with onset of puberty at 10-12 years of age. It helps in development of secondary sexual characters in male. Ex: - moustache, bread, etc. 

Ovary:- At the onset of puberty ovaries begins to secrete oestrogen, a female sex hormone. It produces secondary sexual characters in females and prepares the body for pregnancy. During pregnancy, the ovaries begin to secrete a special hormone help in the development of the baby. 



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