Male: The sperm

About 300 million sperm (spermatozoa) are released in a total volume of 3ml, during ejaculation. Sperm counts below 20 million per ml usually mean that the man is sterile. The sperm are 'cut down' cells. They are adapted for speed by their long flagellum, and their small cytoplasmic volume.

This diagram shows the main features of a spermatozoan.

The cytoplasms lacks most cytoplasmic organelles, but does contain:
mitochondria tightly packed into a sheath in the midpiece, which provide ATP for the energy to drive the movement of the flagellum,
the haploid nucleus, which contains tightly packed DNA, and the
acrosomal vesicle, which contains hydrolytic enzymes, released when the sperm meets the egg.


Around 20% of the sperm are not perfect, but this does not affect fertility. 80% of seminal volume contains fluid secretions from seminal vesicles and prostate.