Paired testes are male reproductive organs (gonads).
Scrotum:
Shortly after birth the testes descent from abdominal cavity into the scrotum (a leather pouch for arrous) which hangs between the thighs. The temperature inside the scrotum is about 34°C composed to 36°C core temperature. Lower temperature is necessary for active sperm production and survival. Muscles elevate or lower the testes, depending on outside air temperature.
Testis:
Each testis contains over eight hundred tightly coiled seminiferous tubules which produce thousands of sperms each second in healthy young man. The walls of the seminiferous tubules are lined with two types of cells.
(1) Spermatogenic cells which give rise to sperms and
(2) Sustentacular cells which nourish the sperm and also secrete a fluid (also hormone inhibin) into the tubules to provide a liquid medium for the sperm.
Between seminiferous tubules are clusters of endocrime cells called interstitial cells (leydig cells) that secrete the male sex hormone the testosterone.
Duct system:
A system of tubes carries the sperm that the testes produce to the penis. Seminiferous tubules merge into a network of tiny tubules called the rete testis which merges into a coiled tube called epididymis which has three functions:
(1) It stores sperms until they are mature and ready to be ejaculated.
(2) It contains smooth muscle that helps propel the sperm toward the penis by peristaltic contractions and
(3) It serves as a duct system for sperm to pas from the testis to the ductus deferens which is dilated continuation of epididymis. Continuing upward after leaving the scrotum, ductus deferens passes through lower part of abdominal wall via inguinal canal. The ductus deferens then passes around the urinary bladder and enlarges to form ampulla. The ampulla stores some sperms until they are ejaculated. Distal to the ampulla the ductus deferens becomes the ejaculatory duct. The urethra is the final section of reproductive duct system.
Accessory glands:
They add their secretions to the sperm as they are propelled through the ducts. Paired seminal vesicles secrete water, fructose, prostaglandins and vitamin C. This secretion provides an eargy source for the motile sperm and helps to neutralize the natural protective acidity of vagina (pH of vagina is about 3 to 4 , but sperm mutility and fertility are enhanced when it increases to about 6). The prostate gland secretes water, enzymes, cholesterol, buffering salts and phospholipids.
Bulbourethral glands secrete a clear alkaline fluid that lubricates the urethra to facilitate the ejaculation of semen and lubricates the penis prior to sexual intercourse. The fluid that results from the combination of sperm and glandular secretions is semen. Penis carries urine through urethra to outside during urination. It also transports semen through urethra during ejaculation.
Penis contains strands of erectile tissue corporex cavernosa and corpus spongiosum. Tip of Penis is covered by prepuse.
Hormonal control of male organs:
Male sex hormones are collectively called androgens. Interstitial cells produce male sex hormones testosterone. When level of testosterone in the blood decreases, the hypothalamus is stimulated to secrete GnRH (Gonadotropin releasing hormone). GnRH stimulates the secretion of FSH (follicle stimulating hormone) and LH (luteinizing hormone) into blood stream. FSH causes spermatogenetic cells in the seminiferous tubules to initate spermatogenesis and LH stimulates the intersticial cells to secrete testosterone. The cycle is complete when testosterone inhibits the secretion of LH and another hormone inhibin is secreted. Inhibin inhibits the secretion of FSH from anterior pituitary. This cycle maintains a constant rate of spermatogenesis.
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