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Spermatozoa (sperm)

A group of sperm, with detail of a single sperm.

Spermatozoa (sperm) are the male sex cells that carry genetic material. They are so tiny that they can't be seen without a microscope. One ejaculation usually contains between 20 million and 600 million sperm.

Sperm have an oval head, a short middle, and a long tail. They move by whipping their tails. A sperm fertilizes an egg (ovum) by breaking through the membrane that surrounds the egg.

Sperm develop in the testicles. They are added to semen before ejaculation.

Current as of: May 1, 2026

Author: WebMD Ignite Staff
Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

Current as of: May 1, 2026

Author: WebMD Ignite Staff

Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.