02 Reproduction in Lower and Higher Animals - part 03 - Male Reproductive System

02 Reproduction in Lower and Higher Animals - part 03 - Male Reproductive System


Male Reproductive System : 

  • It consists of the primary male organ (gonad) called testes, the accessory ducts and glands which form internal and external genitalia.
1. Testes: 
  • A pair of testes, mesodermal in origin,are formed in the lower abdominal cavity. 
  • They are located in a pouch called scrotum. 
  • During early foetal life, the testes develop in abdominal cavity and later they descend into the scrotal sac through a passage called inguinal canal.
  • Each testis is oval in shape, 4 to 5cm long, 2 to 3cm wide and 3cm thick.
Histology of Testis: 

  • The testis is externally covered by a collagenous connective tissue layer called tunica albuginea. 
  • Outer to it is an incomplete peritoneal covering called tunica vaginalis, and inner to it is tunica vasculosa, a thin membranous and vascular layer. 
  • Fibers from tunica albuginea divide each testis into about 200-300 testicular lobules (refer dig. 2.3 L. S. of testis). 
  • Each with 1-4 highly coiled seminiferous tubules. 
  • Each seminiferous tubule is internally lined by cuboidal germinal epithelial cells .(spermatogonia) and few large pyramidal cells called Sertoli or sustentacular cells.
  • The germinal epithelial cells undergo gametogenesis to form the spermatozoa.
  •  Sertoli cells provide nutrition to the developing sperms. 
  • Various stages of spermatogenesis can be seen in the seminiferous tubules - 
  1. The inner most spermatogonial cell (2n)
  2. Primary spermatocyte (2n)
  3. Secondary spermatocyte (n)
  4. Spermatids (n) and
  5. Sperms (n). 
  • The Interstitial or Leydig's cells lie in between the seminiferous tubules. They secrete the male hormone androgen or testosterone.
Do you know ? 

  1. Presence of the peritoneal coveringaround the testis is an indication of its abdominal origin.
  2. The testis are suspended in the scrotum by the spermatic cord. 
  3. Testosterone hormonestimulates the descent of testis and the fibro-muscular band called gubernaculum in the scrotum.
  4. In some males a loop of the intestine may pass through the inguinal canal into the scrotum and cause a condition called inguinal hernia
2. Accessory ducts: 
  • The accessory ducts include -
  1. rete testis
  2. vasa efferentia
  3. epididymis
  4. vas deferens
  5. ejaculatory duct and 
  6. urethra. 
  • All the seminiferous tubules of the testis at the posterior surface form a network of tubules called rete testis. 
  • 12-20 fine tubules arising from rete testis are vasa efferentia. 
  • They carry the sperms from the testis and open into the epididymis. 
  • It is a long and highly coiled tube which is differentiated into -  
  1. an upper caput
  2. middle corpus and 
  3. lower cauda epididymis. 
  • The sperms undergo maturation in epididymis. 
  • Posteriorly it leads into the vas deferens which travels upto the abdominal cavity and loops over the ureter to open into the urethra. 
  • Before doing so, it joins the duct of seminal vesicle to form the ejaculatory duct. 
  • The ejaculatory duct passes through the prostate gland and opens into the urethra. 
  • The urethra provides a common passage for the urine and semen and hence is also called urinogenital duct. 
  • In males the urethra is long and extends through the penis. It opens to the outside by an opening called the urethral meatus or urethral orifice. 
  • All the accessory ducts except urethra are present in pairs.
3. Glands: 
  • The male accessory glands are as follows: 
I. Seminal vesicles: 
  • It is a pair of glands lying on the posterior side of urinary bladder. 
  • It secretes an alkaline seminal fluid which contains - 
  1. fructose
  2. fibrinogen and 
  3. prostaglandins. 
  • It contributes about 60% of the total volume of the semen. 
  • Fructose provides energy for sperm movement while fibrinogen coagulates the semen into a bolus for quick propulsion in the vagina. 
  • The prostaglandins stimulate reverse peristalsis in vagina and uterus aiding faster movement of sperms towards the egg in the female body. 
II. Prostate gland: 
  • It is a large and single gland made up of 20-30 lobes and is located underneath the urinary bladder.
  •  It surrounds the urethra and releases a milky white and slightly acidic prostatic fluid into the urethra. 
  • It forms about 30% of volume of semen. It contains citric acid, acid phosphatase and various other enzymes. 
  • The acid phosphatase protects the sperms from the acidic environment of vagina.
Always Remember : 
  • Prostate cancer is cancer of the prostate gland. 
  • Men who are over 50 years of age and have a daily high consumption of fat, have an increased risk of prostate cancer.
3. Cowper's gland / Bulbourethral gland : 
  • It is a small, pea sized and paired gland situated on either side of urethra. 
  • These glands secrete an alkaline, viscous, mucous like fluid which acts as a lubricant during copulation. 
Semen : 
  • It is the viscous, alkaline and milky fluid (pH 7.2 to 7.7) ejaculated by the male reproductive system. 
  • Normally 2.5 to 4.0 ml of semen is given out during a single ejaculation and it contains about 400 million sperms. 
  • It contains secretion of the epididymis and the accessory glands for nourishing (fructose), neutralizing acidity (Ca++, bicarbonates), activation for movement (prostaglandins). 
4. External genitalia: 
  • It includes -
  1. The penis and 
  2. The scrotum. 
 i. The penis :

  • Male copulatory organ. 
  • Cylindrical and muscular with three bundles of erectile tissue- 
  1. a pair of postero-lateral tissue called corpora cavernosa and 
  2. a median corpus spongiousm. 
  • The swollen tip of the penis is called glans penis. 
  • It is covered by a loose fold of skin called foreskin or prepuce. 
ii. Scrotum : 
  • Loose pouch of pigmented skin lying behind the penis
  • Divided into a right and left scrotal sac by a septum of tunica dartos made of smooth muscle fibres. 
  • The foetal testes are guided into and retained in the scrotum by a short fibro muscular band called gubernaculum. 
  • The testes remain suspended in scrotum by a spermatic chord. 
  • Failure of testis to descend into scrotum is called cryptorchidism. 
  • The failure also results in the sterility. 
  • The cremaster and dartos muscles of scrotum help in drawing testes close or away from the body. This helps in maintaining the temperature of the testis 2-30C lower than the normal body temperature, necessary for spermatogenesis. 

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