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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.


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.

 

The Female Reproductive System

It is located in the pelvic region. It includes:
  • A pair of ovaries
  • A pair of oviducts
  • Uterus
  • Cervix
  • Vagina
  • External genitalia


Ovaries

  • They are the primary female sex organs. They pro…

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