At plays a important role in the penetration
At the anterior end it has a cup-like structure called acrosome made up of Golgi apparatus.
It contains hydrolyzing enzymes and plays a important role in the penetration of sperm in the ovum.
Head in its interior contains a well condensed nucleus and a very little cytoplasm. Head is followed by a short neck. Neck consists of a pair of centrioles, a proximal centriole and a distal centriole.
The two centrioles lie at right angles to one another. The proximal centriole has no active function but is a potential activist within the egg during the first cleavage division of the fertilized egg.
The distal centriole serves as basal body for the tail. Neck is followed by mid-piece which is composed exclusively of mitochondria which aggregate about its basal end, forming a continuous spiral.
This mitochondrial apparatus provides a ready energy source (ATP) to the sperm tail for its motility.
The mid-piece is followed by the principal-piece which ultimately ends in a end-piece. In principal-piece and end-piece the fibre system is reduced to the axial complex of two central fibres surrounded by the ring of nine peripheral fibres.
Throughout the principal-piece, there occurs a surrounding fibrous helix which is composed of semicircular ribs that articulate with one another on opposite sides of the sperm tail.
Numbers of Spermatozoon:
About 300 to 400 millions of sperm cells are present in the semen of each ejaculate of a normal young adult male but of those only one can fertilize each egg cell.
The rest die within three days, retaining their fertilizing ability for only 24 hours. The other sperm cells apparently play an accessory role, however, perhaps by bringing about chemical changes necessary for fertilization.
Males that produce less than 35 millions of sperms per milliliter of semen are generally sterile.