With the help of labelled diagram describe the structure of human sperm.

Answer:

[Figure: Human sperm — head with acrosome cap over the nucleus; short neck with proximal and distal centrioles; middle piece with axial filament surrounded by mitochondrial spiral and ring centriole at its end; long tail with axial filament covered by a thin sheath ending in a naked end piece.]

A human sperm is a microscopic, motile, flagellated cell about 60 µm long. It has four parts:

1. Head: flattened and oval; contains a large haploid nucleus and, at its tip, a cap-like acrosome (derived from Golgi body) containing enzymes (hyaluronidase, acrosin) that help to penetrate the egg membranes.
2. Neck: very short; contains the proximal centriole (helps in the first cleavage of the zygote) and the distal centriole (gives rise to the axial filament).
3. Middle piece: contains the axial filament surrounded by a spirally coiled mitochondrial sheath (nebenkern) that provides energy (ATP) for movement; a ring centriole lies at its end.
4. Tail: long and slender; the axial filament is surrounded by a thin cytoplasmic sheath; its lashing movement propels the sperm forward.