Acrosome

The acrosome is an organelle that develops over the anterior (front) half of the head in the spermatozoa (sperm cells) of humans and many other animals.

In placental mammals, the acrosome contains degradative enzymes (including hyaluronidase and acrosin).

[1] These enzymes break down the outer membrane of the ovum,[2] called the zona pellucida, allowing the haploid nucleus in the sperm cell to join with the haploid nucleus in the ovum.

[4] This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample by flow cytometry[5] or fluorescence microscopy.

[6] In the case of globozoospermia (sperm with round heads), the Golgi apparatus is not transformed into the acrosome, causing male infertility.