Gametogenesis:
The process of formation of gametes in the gonad is called gametogenesis (sperm in testis & ova in ovary).
Spermatogenesis:
The process of formation of sperms is known as spermatogenesis. This process is distinguished into three phases.
- Multiplication phase
- Growth phase
- Maturation phase.
Multiplication phase:
Each seminiferous tubules of testis is lined with germinal cells. The germ cells multiply repeatedly to form spermatogonia containing diploid number of chromosomes (2n)
2. Growth phase:
The spermatogonia increase in size by the accumulation of nourishing material & attain maturity and mature spermatogonia are termed as
primary spermatocytes.
3. Maturation phase:
Each primary spermatocyte under goes reduction division (meiotic-I) to form secondary spermatocytes and secondary Spermatocytes again undergo mitosis division to form spermatids. Each spermatid later on metamorphoses into a sperm which has a small head with a nucleus & a long tail.
Oogenesis:
The process of formation of ova from the germ cells of the germinal epithelium of ovary is called oogenesis. It is completed in three phases.
- Multiplication phase
- Growth phase
- Maturation phase
- Multiplication phase: The primary germ cells of the germinal epithelium undergo repeated divisions & ultimately form the oogonia.
Growth phase: In this phase oogonia increases in size by the accumulation of yolk to form primary oocytes.
- Maturation phase: The primary Oocytes undergo two successive divisions. The first maturation division by meiotic to form a secondary oocyte. The second maturation division takes place with an unequal division of the cytoplasm, resulting in the formation of a large ovum & small second polar body.
