The pineal gland is a cone shaped gland situated on the roof of the third ventricle of the brain. It produces melatonin. It is involved in the circadian rhythm and the rhythm of day and night. Melatonin secretion decreases in the day and increases at night.
It is located in the upper part of the Thorax very close to the heart. It is a soft, pinkish and bilobed mass. It reaches its maximum size at 10-12 years of age and gradually decreases in size. Itss function stops after the age of 50. It produces a hormone called thymosin. It is responsible for the maturation of a special type of white blood cells called t-lymphocytes. These cells originate in the blood marrow and migrate to the thymus gland where they mature.
-It stimulates the secretion of gastric juice and causes the contraction and movement of the stomach.
-It causes the release of sodium bicarbonate solution, from pancreas for pancreatic juice and from liver for bile juice.
-It stimulates pancreas to release its enzymes and stimulates the gallbladder to release bile juice into the duodenum.
-It stimulates crypts of Lieberkuhn to secrete enzymes in the intestinal juice.
-Tt stimulates Brunner's glands to release mucus
-It converts angiotensinogen to angiotensin that plays an important role in maintaining blood volume.
-It stimulates the bone marrow to increase the production of red blood cells.
-It promotes the absorption of calcium ions and phosphorus in the small intestine and accelerates bone formation.
Hormones produced by reproductive organs
-They release hormones called androgens. The principal androgen is testosterone. It stimulates spermatogenesis and develop secondary sexual characters like beard and moustache at 17
-They produce oestrogens, progesterone, human placental lactogen, relaxin,etc. They stimulate maturation of ova, uterine epithelium, mammary glands, etc.