Sperm: the male sex cells

The mature sperm cell (see Figure 5.1) is a little swimming male sex cell. It consists of a head, body and tail. The head is covered by a cap and contains a nucleus of dense genetic material. It is attached to a region containing mitochondria, which supply the energy for the sperm's activity. The tail is able to contract and relax, producing a characteristic wave-like movement.


Figure 5.1 The structure of a sperm, the male sex cell.

Look at Figure 5.1. Can you explain how sperm move up the vagina, into the uterus and along the fallopian tubes?

Show answer

The sperm make up only about 5% of what a man ejaculates during the sex act. This represents about 100 to 400 million sperm each time, carried in a nutritious fluid (semen) which helps to keep them alive. Sperm are very, very small in size; in fact, a single sperm is the smallest cell in the male body.

From puberty onwards, new sperm develop in the testes (testicles) throughout a man's adult life. It takes about 72 days for one sperm to develop to maturity. Sperm production requires a temperature which is 3 to 5°C below body temperature -- which is why the testicles are outside the abdomen, where they can remain a little cooler. Exposure of the testicles to a higher temperature will inhibit sperm production and may lead to infertility.

Last modified: Tuesday, 7 October 2014, 9:02 AM