Sex cells

• Features of a sperm cell


  The head contains the genetic material for fertilisation in a haploidnucleus. The acrosome in the head contains enzymes so that a sperm can penetrate an egg. The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim. Sperm are the smallest cells in the body and millions of them are made.
• Egg cell


  The cytoplasm contains nutrients for the growth of the early embryo. The haploid nucleus contains the genetic material for fertilisation. The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter. Eggs are one of the biggest cells in the body and only a few are made.