Male Reproductive System
A man's fertility unfolds in a similar manner as a woman's. The hypothalamus gland stimulates the pituitary to produce FSH and LH, which initiate production of the gamete (sperm for men ovum for women). Sperm production begins in the testicles.
From the testicles sperm travel to the epididymis where maturation takes place. Once mature they travel up the vas deferens and wait in the ampulla of the vas deferens for ejaculation. Should ejaculation not occur sperm is reabsorbed by the body.
On either side of the ampulla of the vas deferens are seminal vesicles, which produce a fluid high in fructose that help sperm survive.
When the man is ready to ejaculate the sperm travels through the prostate gland where they mix with seminal fluid produced by the prostate. They then travel through the urethra and out of the penis in seminal fluid – sperm and seminal fluid together is called semen.
Prior to ejaculation, the Cowper's gland, in front of the prostate, releases pre-ejaculatory fluid. This fluid cleanses and alkalinizes the urethra so that sperm can survive their passage out of the penis.
Sperm are produced continuously from puberty until old age. As the man ages his fertility declines as the number and viability of his sperm are reduced. Though regardless of age, a man is considered more or less fertile all the time. In contrast, the woman is fertile for only a few days each cycle, and her fertility lasts for only 25-40 years.