Spermatids (Sperm in Training)

The last step before sperm

When a secondary spermatocyte splits, it makes two spermatids. They sit near the middle of the tiny tubes in the testes.

At first they are small, round cells. Each has a nucleus with half the usual DNA.

Big helper cells called Sertoli cells hold them and feed them while they change.

A big makeover

• The DNA gets packed very tightly into a small head.
• A cap forms on the front of the head.
• Mitochondria line up behind the head to make a power pack.
• A long tail grows.
• Extra bits the cell doesn't need get trimmed away.

When the makeover is done, the spermatid has become a sperm cell.

Spermatid quiz