Describe briefly the structure of a human sperm.

Explanation

Sperm is a male gamete produced in the testes by spermatogenesis. The shape and the size of the sperm varies frog species to species. However all the animal sperms show a common structure.
Typical structure of sperm shows four regions. They are
(a) Head
(b) Neck
(c) Middle piece
(d) Tail
(a) Head: Head is the anterior segment of the sperm which is oval in shape. Head includes a haploid sperm nucleus and a little cytoplasm. The sperm is devoid of yolk. The head is covered by a cap like structure called acrosome, containing hydrolytic enzymes. Acrosome helps the sperm to penetrate ovum. Acrosome is formed by golgi apparatus.
(b) Neck: It is an indistinct part that connects the head and the middle piece. it includes a proximal centriole close to the sperm nucleus.
(c) Middle piece: It contains a distal centriole and an axial filament. Surrounding the axial filament mitochondrial sheath is present which provides energy needed for the movement of the sperm. Hence middle piece may also be referred to as engine room of the sperm. Axial filament is also called axoneme and arises from the distal centriolo which forms the axis of the tail.
(d) Tail: It is divided into two parts namely
,1. Main picce: It is covered by a cytoplasmic sheath.
2. End piece: It is naked and forms the terminal part of the tail. The tail shows lateral undulating motion and bring about the propulsion of the sperm.