9. Testis (Male Gonad)
- It is the male primary sex organ and an endocrine gland.
- A pair of testis is present in the scrotal sac.
- It is formed of seminiferous tubules and interstitial (stromal) tissues.
- Leydig (interstitial) cells in the inter-tubular spaces produce hormones called androgens (mainly testosterone).
Functions
- Regulate development, of the accessory sex organs.
- Spermatogenesis (production).
- Stimulate sexual behavior (libido), growth of muscles, hairs, aggressiveness.
- Help in anabolism of protein and carbohydrate.
10. Ovary (Female Gonad)
- It is the female primary sex organ.
- A pair of ovaries is located in the abdomen.
- It produces one ovum during each menstrual cycle.
- Ovary is formed of ovarian follicles and stromal tissues.
- Ovarian follicles produce Estrogen (a steroid hormone).
- After ovulation, ruptured follicle forms a structure called Corpus luteum. It secretes progesterone (a steroid hormone).
Functions of Estrogen
- Growth and activities of female secondary sex organs.
- Development of ovarian follicles & mammary glands.
- Female secondary sex characters (e.g. high pitch voice) and sexual behavior.
Functions of Progesterone
- It supports pregnancy.
- It acts on mammary glands to stimulate formation of alveoli (sacs to store milk) and milk secretion.
Hormones of Heart, Kidney & Gastrointestinal Tract
1. Atrial wall of heart
- Produce a peptide hormone called Atrial natriuretic factor (ANF).
- When BP increases, ANF causes dilation of blood vessels to reduce the BP.
2. JGA of kidney
- Produces Erythropoietin (peptide hormone).
- Erythropoietin stimulates erythropoiesis (formation of RBC).
3. Gastro-intestinal tract
- Produce peptide hormones. E.g.
- Gastrin: Stimulates gastric glands to secrete HCl and pepsinogen.
- Secretin: Stimulates exocrine pancreas to secrete water and bicarbonate ions.
- Cholecystokinin (CCK): Stimulates secretion of bile from gall bladder and pancreatic enzymes from pancreas.
- Gastric inhibitory peptide (GIP): Inhibits gastric secretion.
- Several other non-endocrine tissues secrete hormones called growth factors. These help for the normal growth of tissues and their repairing or regeneration.