MALE REPRODUCTIVE SYSTEM
THE TESTES
Glandular organs located in the scrotum, testes are oval suspended by spermatic cord, which is a fibrous connective tissue containing seminal duct, testicular artery, vein, lymphatic vessels and nerves. In fetal life, testes are located in the abdomen but descend into the scrotum before birth.
Scrotum is a skin-covered pouch lying below pubic symphysis in front of the thighs. The dartos muscle (muscle of the scrotum) divides the scrotum into two compartments each containing the left and right testes. Each testes is about 4 cm long, 3 cm wide and 2 cm thick, covered by several membranes. The innermost capsule layer divides the inside into small lobules (more than 200 in number) and each lobule contains fine coiled seminiferous tubule and numerous interstitial cells (Leydig cells). The seminiferous tubules finally join together and form plexus from where ducts come out and enter the head of the epididymis
FUNCTIONS OF TESTES
1. Spermatogenesis 2. Secretion of hormone - Testosterone
Spermatogenesis or formation and maturation of sperms begins in the seminiferous tubules in a layer of cells (spermato- gonia) near the outer margin of each tubule, Spermatogonia undergo continuous mitotic cell divisions giving rise to new cells available for producing sperm. Some of these cells begin to move into the hollow centre and develop into primary spermatocytes which in turn undergo further cell division forming secondary spermatocytes and finally following another cell division gives rise to spermatods. Spermatods although contain all the necessary chromosomes to fertilize an egg cell yet are not mature enough for this function. A further maturation involves the addition of a very active tail and a loss of nearly all cellular cytoplasm resulting into a mature spermatozoan Each spermatozoan has a head, neck, body and tail region each with its unique characteristic and capabilities.
The other function of the testes is secretion of hormones mainly testosterone which has following main functions:
1. Development and maintenance of:
✓ male secondary sex characteristics,
✓accessory organs like prostate, seminal vesicles, and
✓sexual/emotional behaviour.
2. Protein metabolism: Testosterone is considered an anabolic hormone as it promotes protein metabolism and is responsible for greater muscle and bone development.
3. Has a negative feedback on anterior pituitary secretion of FSH and ICSH which in turn stimulate spermatogenesis and testosterone secretion from testis.
DUCTS OF TESTES
Epididymis: Lying along the top of the testes each epididymis consists of a coiled tube about 20 feet in length and less than 1 mm in diameter. This forms one of the first ducts to carry sperms from within the testicle and lead them to the vas deferens. One of the functions of the epididymis is to store the spermatozoa for short periods of time, also here the spermatozoa complete their process of maturation.
• Vas deferens (seminal duct): Vas deferens are a further extension of epididymis which are rather enlarged and straightened out. These pass through the inguinal canal, where it is enclosed in a fibrous tube, the spermatic cord into the abdominal cavity extend atop the posterior surface of the bladder Ducts from seminal vesicles join with vas deferens forming ejaculatory ducts . Ejaculatory ducts pass through the prostate gland to terminate in the urethra.
Seminal vesicles, prostate, and bulbourethral glands form the accessory reproductive glands. Secretions of these glands provide nourishment and optimum pH, etc. for spermatozoa. Thus, semen (seminal fluid) consists of spermatozoa and secretions of all these accessory glands. Semen contains fructose, prostaglandins, calcium, and its pH is alkaline. Human semen is liquid when ejaculated but soon coagulates in vitro or in vagina and after 15-20 min. it undergoes a secondary liquefaction.
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