Write a note on human sperm
Structure of the Sperm (Spermatozoan) : -
(Sperm = seed, zoon = animal)
It is microscopic, elongated haploid motile male gamete or paternal gamete measuring about 0.055 mm (60 mu) in length. Sperm remains viable for seventy – two hours, but can fertilize the ovum in first 12 to 14 hours only.
Head: It is flat and oval region consisting of a large nucleus and an acrosome. Acrosome secretes hydrolytic enzymes like hyaluronidase which helps in penetration of the egg during fertilization. The acrosome and anterior half of nucleus is covered by a fibrillar sheath.
Neck: It is a very short region having two centrioles. The proximal centriole plays a role in the first cleavage of the zygote. The distal centriole gives rise to the axial filament of the sperm.
Middle piece: It serves as the powerhouse for sperm. It has many mitochondria spirally coiled
(Nebenkern) around the axial filament. The mitochondria provide energy for the movement of the sperm in the female genital tract. Posterior half of nucleus, neck, middle piece of sperm are covered by a sheath.
Tail: The tail is long, slender and tapering structure formed of cytoplasm. A fine thread, the axial filament arises from the distal centriole and traverse the middle piece and tail.