The acrosome reaction is an important reproductive function which assists a sperm to break through the shell of the egg and enter its nucleus for fertilisation. Each sperm cell has an acrosomal cap, which contains a capsule of enzymes that breakdown the shell of the egg in the process known as the acrosome reaction. This process only occurs if a sperm comes into close proximity with an egg.

When the acrosome reaction occurs, the acrosomal cap lengthens into a tube (acrosomal tube) which fuses with the outer layer of the egg. It releases the enzymes which break down the oocyte’s zona pellucida (shell). Once the shell is broken down, the sperm is able to penetrate the shell and enter the nucleus of the oocyte, through the acrosome tube. The sperm and egg can then combine their chromosomes to complete the fertilisation process.


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