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Anatomy -Thymus gland
The thymus gland is located behind the sternum and between the lungs. It produces the hormone thymosin, which is required for the development of T-lymphocytes and cell-mediated immunity, and is only active until puberty when it begins to shrink and be replaced by fat. Several tissues produce local hormones like histamine, serotonin, prostaglandins, and erythropoietin that act near their site of secretion to carry out functions like mediating inflammation, contracting smooth muscle, increasing capillary permeability, and stimulating red blood cell formation. Gastrointestinal hormones such as gastrin, secretin, and cholecystokinin also influence secretion of digestive juices.
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Anatomy -Thymus gland
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- 3. THYMUS GLAND It islocated behind sternum and between lungs, is only active until puberty. After puberty, the thymus starts to slowly shrink and become replaced by fat.
- 4. THYMOSIN This is thehormone secreted by the thymus gland and is required for the development of T- lymphocytes for cell mediated immunity .
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- 7. LOCAL HORMONES A numberof body tissues not normally described as endocrine glands secrete substances that act locally.
- 8. HISTAMINE This hormone issynthesized by mast cells in the tissues and basophils in blood.
- 9. It is releasedas part of the inflammatory process, increasing capillary permeability and dilatation.
- 10. It also causescontraction of smooth muscle of the bronchi and alimentary tract and stimulates the secretion of gastric juice.
- 11. SEROTONIN (5-HYDROXYTRYPTAMINE, 5-HT) This ispresent in platelets, in the brain and in the intestinal wall.
- 12. It causes intestinalsecretion and contraction of smooth muscle and its role in haemostasis (blood clotting) .
- 13. PROSTAGLANDINS (PGS) These arelipid substances that act as local hormones and have wide-ranging physiological effects in:
- 14. The inflammatory response potentiatingpain fever regulating blood pressure blood clotting uterine contractions during labour.
- 15. Other chemically similarcompounds include leukotrienes and thromboxanes.
- 16. They are activesubstances found in only small amounts, as they are rapidly degraded.
- 17. ERYTHROPOIETIN This hormone issynthesised by the kidneys and increases erythropoiesis (the rate of red blood cell formation.
- 18. GASTROINTESTINAL HORMONES Several local hormones, includinggastrin, secretin and cholecystokinin (CCK), influence the secretion of digestive juices.
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