New sperm cells are generated in the testes in specialized tubes called The tubules contain Sertoli’s cells (which secrete hormones required for spermatogenesis) and germ cells, from which sperm cells are made. In the final stage of spermatogenesis:
the characteristic sperm cells are produced;
DNA material (chromosomes) is condensed into the head of the sperm cell;
the cap or head of the sperm cell (acrosome) - which contains special enzymes that help to penetrate the egg - is made;
the sperm tail (flagellum) is produced; and
the fluid inside the cell is reduced.
Roughly 100 million sperm cells are produced each day. It is said that an average of 50–200 million sperm cells are present in each ejaculate. Reactive oxygen species (ROS) pose the greatest threat to the integrity of sperm. DNA damage from ROS can reduce sperm viability or result in non-viable or damaged embryos. It takes about 3 months to regenerate sperm in the testes.