The male genitals are the testicles (testes), the duct system (made up of the epididymis and the deferent duct), the accessory glands (seminal vesicles and prostate gland) and the penis.

The deferent duct or vas deferens is continuous with the epididymis, which connects it to the prostatic urethra. All boys are born with a foreskin, a fold of skin at the end of the penis that covers the glans (head).

The penis, which usually hangs limp, becomes hard when a male is sexually excited. When this happens, the tissues inside the penis fill with blood, and the penis becomes stiff and erect. This is called an erection. When the erect penis is stimulated, muscles around the reproductive organs contract and force the semen through the duct system and urethra. Semen is pushed out of the male's body through his urethra — this process is called ejaculation. Each ejaculation can contain 2-6 ml of sperm. 1 ml of sperm contains 100 million male gametes.

Sperm cells are produced in the testes (singular testis) and stored in the epididymis. Compared to the abdominal cavity, the temperature required for sperm to form is a few degrees lower than the individual's body temperature.

Sperm cells are 0.06 millimeters long. In the main part of the cell, there is a nucleus (with a so-called haploid or simple (n) genome). The mitochondria of the middle part release energy for movement. The tail of the sperm cell helps it to move.