Human Reproduction - The Male Reproductive System

The male reproductive system:

• The male reproductive system is located in the pelvis region.
  

  Diagrammatic sectional view of a male pelvis showing reproductive system

• Male reproductive system includes:

• A pair of testes (primary sex-organ)
• Accessory ducts (rete testis, vas a efferentia epididymis, vas deferens)
• Accessory glands (paired seminal vescile, a prostate, and paired bulbourethral gland)
• External genitalia (Penis)
  

  Diagrammatic view of male reproductive system

• The testes are situated outside the abdominal cavity within a pouch called scrotum.
• The scrotum helps in maintaining the low temperature of the testes (2-2.5^oC lower than the normal internal body temperature) necessary for spermatogenesis.
• In adults, each testis is oval in shape, with a length of about 4 to 5 cm and a width of about 2 to 3 cm.
• The testis is covered by a dense covering.
• Each testis has about 250 compartments called testicular lobules.

L. S. of testis 

Histology of Seminiferous tubules:

• Each lob contain one to three highly coiled seminiferous tubules in which sperms are produced.
• Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and Sertoli cells.
• The male germ cells undergo meiotic divisions finally leading to sperm formation, while Sertoli cells provide nutrition to the germ cells.
• The regions outside the seminiferous tubules called interstitial spaces contain:
  1) Small blood vessels
  2) Interstitial cells or Leydig cells
  3) Other immunologically competent cells
• Leydig cells synthesise and secrete testicular hormones called androgens, also called male sex hormones.

  Diagrammatic sectional view of seminiferous tubule

B) Accessory ducts:

• The male sex accessory ducts include rete testis, vasa efferentia, epididymis, and vas deferens.
• The seminiferous tubules of the testis open into the vasa efferentia through rete testis.
• The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis.
• The epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder.
• Vas deferens receives a duct from seminal vesicle and opens into the urethra as the ejaculatory duct, that stores and transports sperm from the testis to outside via urethra.
• The urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.

C) Accessory glands:

• The male accessory glands include paired seminal vesicles, prostate, and paired bulbourethral glands.
• Secretion of all these glands are constitutively called seminal plasma which is rich in fructose, calcium, and certain enzymes.
• The secretions of bulbourethral glands also helps in the lubrication of the penis.

D) External genitalia:

• The penis is the male external genitalia.
• Penis is made up of special tissue that helps in erection of the penis to facilitates insemination.
• The enlarged end of penis called the glans penis is covered by a loose fold of skin called foreskin or prepuce.

Puberty / Sexual maturity in Males: 

• Puberty is the age at which the reproductive system becomes functional, sex organs begin to produce gametes and sex hormones.
• In males the onset of puberty occurs at age 12-15 years. Under the influence of testosterone, secondary sexual characters appear. Thereafter, it remains functional throughout life.