Unlike women’s reproductive organs, men’s reproductive organs are found entirely outside the body.

Male Reproductive System

Testicles and Scrotum

The testicles (balls) are the male equivalent of a woman’s ovaries. It is inside these that sperm are made and important male hormones produced. There are two testicles, roughly the size of small plums, and they are protected in a soft pouch of skin called the scrotum.

The scrotum hangs outside the body just behind the penis and between the legs. This keeps the testicles cool – the average body temperature (37°C) is too hot to produce healthy sperm. They are very sensitive to heat and if they get too hot the scrotum drops down to cool off and when they are cold it shrinks closer to the body to keep warm.

Male Hormones

Hormones are just as important for reproduction in men as they are in women. The testicles produce the male hormone testosterone. It is responsible for sperm production and growth and is important for male sex drive. It also controls male characteristics such as hair growth and the deepening of the voice.


Inside each testicle are about 1,000 tightly coiled tubes. Individual sperm are continuously made in these tubes. The growing sperm travel along the tiny tubes to a larger coiled tube called the epididymis, which is at the top of the testicle. Here they stay until they are fully matured and ready to be ejaculated.


At ejaculation sperm passes along the vas deferens (sperm ducts) to the penis and out of the body through the urethra. On the way, fluid from the seminal vesicles and prostate gland is added to the sperm. This helps nourish and transport them and gives semen (as it is now called) its white creamy appearance. The average ejaculation contains up to 300 million sperm and will fill a small teaspoon.

Sperm – did you know?

  • Boys start to produce sperm at puberty, the time when their body goes through changes from a boy to a man.
  • It takes about 70 days for a sperm to be produced, but as production is a continuous process there is always plenty of fully mature sperm at any one time.
  • Sperm are minute – only 1/25mm long and 1/250mm wide, which is about a hundred times smaller than the female egg. Sperm are made up of three parts, a head containing the sex chromosomes, a middle which gives them the energy, and a tail for swimming.
  • On average men produce around 150–1,000 million sperm every day, so they are unlikely to run out.
  • Sperm are excellent swimmers. With the right type of conditions the best swimmers are able to swim through the cervix into the uterus in about two minutes.
  • Sperm are also survivors and can live for up to five days on average inside the woman’s body but up to seven days if the conditions are right.
  • Sperm production can be damaged by untreated sexually transmitted infections, excessive heat, alcohol, smoking, or recreational drugs.

The penis contains erectile tissue which fills with blood when a man is sexually aroused and causes an erection, making the penis longer and thicker. To prepare for ejaculation a small amount of lubricating fluid, known as pre-ejaculation fluid is produced from the Cowper’s glands. This fluid leaks out of the penis before ejaculation and may contain sperm. When a man ejaculates, the muscles of the penis contract forcing the semen out of the penis in spurts. Straight after ejaculation the fluid is thick but it becomes more liquid after a few minutes – this helps to release the sperm.

Reproduced with kind permission from www.fpa.org.uk