- BS Media
- Published: 30, May, 2017 | Updated: May 30, 2017
- Pineal body
- Mucosa of alimentary canal.
Till recently, it was beleived that the pineal gland found in man was a vestigeal organ. It is now known that the pineal body secretes melatonin, which is an antigonadial as it may delay the sexual development.
The pituitary is a small pea-shaped gland situated below the hypothalamus [ventral wall of diencephalon]. It is connected to the hypothalamus by a stalk called "infundibulum". Based on the position the gland is also called "hypophysis" [hypo-below; physis-brain]. Until recently, the pituitary gland was considered to be the "master or chief gland of endocrine system". It is now known that the pituitary itself depends upon the hormones of hypothalamus.
The hypothalamus secretes many hormones called "neurohormones" or "releasing factors". These are transported to the anterior lobe of pituitary through the "hypophyseal portal system". The releasing factors stimulate the pituitary to secrete its hormones.
- L.H and
G.T.H [Gonado tropic hormone ] or gonadotropins:
- "Oxytocin" stimulates the contraction of uterus in pregnant woman during the child birth [parturition].
- A.D.H [Anti diuretic hormone] increases the reabsorption of HzO in the distal convoluted tubule of kidney. Defeciency of A.D.H increases the urine flow and causes the disease called "diabetes insipidus" [Diabete-urine, insipid -tasteless]. Hence the urine is highly diluted. Over secretion of A.D.H. increases the absorption of H20. Hence the urine is highly concentrated.
If the thyroid glands are removed in tadpole larva of frog it fails to undergo metamorphosis. When such thyroid free tadpole larva is fed with thyroid glands, it undergoes metamorphosis. If normal young tad poles are fed with thyroxine, they metamorphose into frogs prematurely [the normal period of metamorphosis is reduced].
- α - cells secrete a hormone called "glucagon". It increases the sugar, glucose level in the blood by glycogenolysis [convertion of glycogen into glucose]. Hence glucagon is described as "hyper glycemic hormone".
- β - cells secrete a hormone called "insulin", [covertion of glucose into glycogen]. So, it lowers the sugar level in the blood. It is described as "hypoglycemic" hormone.