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TNPSC Free Notes Biology- Parathyroid gland

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான  முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Parathyroid gland

 In human, four tiny parathyroid glands are found in the posterior wall of the
thyroid glands.
 This gland is composed of two types of cells, the chief cells and oxyphil
 The chief cells secrete parathyroid hormone (PTH) and the functions of
oxyphil cells are not known.
Parathyroid hormone or Parathormone (PTH)
 PTH is a hypercalcemic hormone.
 It is a peptide hormone involved in controlling the calcium and phosphate
 The secretion of PTH is controlled by calcium level in the blood.
 It increases the blood calcium level by stimulating osteoclasts to dissolve
the bone matrix.
 As a result, calcium and phosphate are released into the blood.
 PTH enhances the reabsorption of calcium and excretion of phosphates by
the renal tubules and promotes activation of vitamin D to increase calcium
absorption by intestinal mucosal cells.

Functions of Parathormone
 The parathormone regulates calcium and phosphorus metabolism in the
 They act on bone, kidney and intestine to maintain blood calcium levels.

Parathyroid Dysfunction

 The secretion of parathyroid hormone can be altered due to the following
conditions. Removal of parathyroid glands during thyroidectomy (removal
of thyroid) causes decreased secretion of parathormone.
 The conditions are Muscle spasm known as Tetany and painful cramps of
the limb muscles.
Thymus gland
 Thymus gland is partially an endocrine and partially a lymphoid organ.
 It is a bilobed structure located just above the heart and aorta, behind the
 It is covered by fibrous capsule and anatomically it is divisible into an outer
cortex and an inner medulla.
 It secretes four hormones such as thymulin, thymosin, thymopoietin and
thymic humoral factor (THF).
 The primary function of thymus is the production of immuno competent
‘T’ lymphocytes which provides cell mediated immunity.
Pancreas (Islets of Langerhans)
 Pancreas is an elongated, yellowish gland situated in the loop of stomach
and duodenum. It is exocrine and endocrine in nature.
 The exocrine pancreas secretes pancreatic juice which plays a role in
digestion while the endocrine portion is made up of Islets of Langerhans.
 The Islets of Langerhans consists of two types of cells namely alpha cells
and beta cells.
 Human pancreas has one to two million islets of langerhans.
 In each islet about 60% cells are beta cells, 30% cells are alpha cells and
10% cells are delta cells.
 The alpha cells secrete glucagon, the beta cells secrete insulin and delta
cells secrete somatostatin.


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