Schematic diagram of a sperm cell, showing the (1) acrosome, (2) cell membrane, (3) nucleus, (4) mitochondria, and (5) flagellum (tail)

A sperm cell, or spermatozoon (pl. spermatozoa) (in Greek: sperm = semen and zoon = alive), is the haploid cell that is the male gamete. It is carried in fluid called semen, and is capable of fertilising an egg cell to form a zygote. A zygote can grow into a new organism, such as a human. Sperm cells contain half of the genetic information needed to create life. Generally, the sex of the offspring is determined by the sperm, through the chromosomal pair "XX" (for a female) or "XY" (for a male). Sperm cells were first observed by Antoni van Leeuwenhoek in 1679.

Sperm structure and size

Individual spermatozoa are highly differentiated cells, composed normally of a head, basal body (or midpiece), and tail. The head contains some cytoplasm and the nuclear material for fertilization. The basal body contains a large concentration of mitochondria that provide the energy for sperm motility through the production of ATP. The spermatozoan tail is typically a flagellum used for propulsion.

In humans, sperm cells consists of a head 5 µm by 3 µm and a tail 50 µm long. The tail flagellates, which we now know propels the sperm cell by rotating like a rutter not side to side like a whip. The cell is characterized by a minimum of cytoplasm.

Sperm production

Main article: Spermatogenesis

Sperm are produced in the seminiferous tubules of the testes in a process called spermatogenesis. Round cells called spermatogonia divide and differentiate eventually to become sperm. During sexual intercourse the sperm is deposited in the vagina - and then it moves to the ovum inside the ovary.

See also

• sperm competition

External link

• The Handbook of Andrology