Human Reproduction

Structure and function of male reproductive system

Human beings reproduce sexually and are viviparous.

In humans, the reproductive phase starts after puberty. It involves:

• Gametogenesis
• Insemination
• Fertilisation
• Implantation
• Gestation
• Parturition

The Male Reproductive System

• It is located in the pelvic region.

• It consists of:

  • A pair of testes

  • Accessory glands and ducts

  • External genitalia

Testes

• Situated within the scrotum, which protects the testes and also helps in maintaining the temperature.

• Each testis is 4 to 5 cm in length, and 2 to 3 cm in width, and has about 250 compartments called testicular lobules.

• Testicular lobules have seminiferous tubules which are the sites of sperm formation.

• Seminiferous tubules are lined by two types of cells:

  • Male germ cells − They undergo meiosis to form sperms.

  • Sertoli cells − They provide nourishment to the germ cells.

• Region outside the seminiferous tubules is called the interstitial space, which contains Leydig cells (interstitial cells). The Leydig cells produce androgens.
• Apart from producing sperms, testes also produce a hormone called testosterone. This hormone is responsible for the development of male sex organs like penis and testes. It also brings about secondary sex characteristics in boys during puberty.

Sperm

A sperm consists of four main regions:

• Head: It contains a nucleus, that carries the genetic material. It also contains a large secretory vesicle called acrosome. It secrets hyaluronidase enzyme, that helps in the entry of sperm into the egg by dissolving the ovum wall.
• ​Neck: It joins the head and middle part.
• Middle Piece: It contains several mitochondria that provide energy (ATP) to the sperm.
• Tail: It helps in the movement of the sperm.

Accessory Ducts and Glands

• Accessory ducts include:

  • Rete testis

  • Vasa efferentia

  • Epididymis

  • Vas deferens

• The seminiferous tubules open into the vasa efferentia through the rete testis.

• The vasa efferentia open into the epididymis, which leads to the vas deferens. The vas deferens opens into the urethra along with a duct from the seminal vesicle called the ejaculatory duct.

• The ejaculatory duct stores the sperms and transports them to the outside.

• The urethra starts from the urinary bladder, extends through the penis and opens via the urethral meatus.

• Accessory glands include:

  • A pair of seminal vesicles

  • Prostate gland

  • A pair of bulbourethral glands

• The secretions of these glands make up the seminal plasma, and provide nutrition and a medium of motility to the sperms.

 

Human beings reproduce sexually and are viviparous.

In humans, the reproductive phase starts after puberty. It involves:

• Gametogenesis
• Insemination
• Fertilisation
• Implantation
• Gestation
• Parturition

The Male Reproductive System

• It is located in the pelvic region.

• …