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Sexual Reproduction in Humans

Sexual Reproduction in Humans Synopsis

Synopsis

 

Secondary Sexual Characters

  • Reproduction is the key process for the continuation of life on earth.
  • Males and females show outwardly differentiating features called secondary sexual characters.

 

Reproductive Organs in Humans

  • Primary Reproductive Organs: Gonads, i.e. testes in males and ovaries in females, which produce gametes.
  • Accessory Reproductive Organs: All structures which help in the transfer and meeting of different kinds of gametes.

 

The Male Reproductive System

 
 
The Female Reproductive System
 
 
 
 
  
 
 
Mammary Glands
  • Breasts are rounded structures present on the ventral thoracic wall.
  • Each breast consists of fatty tissue, connective tissue and mammary glands.
  • Mammary glands contain 15 to 20 mammary lobes which contain cluster of called alveoli.
  • The cells of alveoli secret milk into mammary tubules which unit to form a mammary duct.
  • Mammary ducts join to form a mammary ampulla which is connected to the lactiferous duct through which milk is sucked out.
 
Gametogenesis
  • The process by which male and female sex cells or gametes (sperms and ova) are formed in the male and female gonads (testes and ovaries) is called gametogenesis.
 
Spermatogenesis
  • The process of the formation of spermatozoa or sperms from spore mother cells or spermatogonia of the germinal epithelium lining the seminiferous tubules is called spermatogenesis.
  • It starts in puberty.
  • Some of the spermatogonia called primary spermatocytes undergo first meiotic division and produce secondary spermatocytes.
  • Primary spermatocytes contain 46 chromosomes while the secondary spermatocytes contain 23 chromosomes, hence; the secondary spermatocytes are haploid.
  • The secondary spermatocytes under second meiotic division and form four haploid spermatids.
  • Hence, from one diploid primary spermatocyte four haploid spermatids are produced.
  • Spermatids are transformed to spermatozoa (sperms) by spermiogenesis.
  • After spermiogenesis, sperm heads become embedded in the Sertoli cells. They are released from the seminiferous tubules by spermiation.
 
Hormonal Control of Spermatogensis
  • Increased levels of hypothalamic hormone Gonadotropin releasing hormone (GnRH) acts on the anterior pituitary which then secrete luteinising hormone (LH) and follicular stimulating hormone (FSH).
  • LH acts on Leydig cells and initiates the secretion of androgens.
  • Androgens stimulate the spermatogenesis.
  • FSH acts on the Sartoli cells and stimulates the secretion of some factors necessary for the spermiogenesis.