class-12-biology-ncert-book-chapter-2-human-reproduction-1779570556

Humans are sexually reproducing and viviparous organisms.
Reproductive events in humans include:
- Gametogenesis: Formation of gametes (sperms in males and ovum in females).
- Insemination: Transfer of sperms into the female genital tract.
- Fertilisation: Fusion of male and female gametes leading to the formation of a zygote.
- Implantation: Formation and development of a blastocyst and its attachment to the uterine wall.
- Gestation: Embryonic development.
- Parturition: Delivery of the baby.
Reproductive events occur after the attainment of puberty.
Sexual Dimorphism in Reproductive Longevity:
- Sperm formation continues even in old men.
- Formation of the ovum ceases in women around the age of $50$ years.

Location: Situated in the pelvis region.
Components: Includes a pair of testes, accessory ducts, glands, and external genitalia.
The Testes:
- Situated outside the abdominal cavity within a pouch called the scrotum.
- Scrotum Function: Helps in maintaining the low temperature of the testes ( $2-2.5^\circ C$ lower than the normal internal body temperature) which is necessary for spermatogenesis.
- Shape and Size: Oval in shape; length of about $4-5\,cm$ and a width of about $2-3\,cm$ .
- Structure: Covered by a dense covering. Each testis contains approximately $250$ compartments called testicular lobules.
- Seminiferous Tubules: Each lobule contains $1$ to $3$ highly coiled seminiferous tubules where sperms are produced.
- **Cellular Lining of Semin