A tadpole-shaped cell with a cap of digestive enzymes on the head, a mitochondrial midpiece and a whiplike tail
Sperm cell â the acrosome, midpiece and flagellum.
Anatomy · Cells & tissues
Sperm cell
The male gamete
Reproductive system · male germ cell
The male reproductive cell: a streamlined, swimming cell about 50â60 micrometres long, made up of a head, a midpiece and a tail. The head is a small oval packed with 23 tightly coiled chromosomes and capped by the acrosome, a bag of enzymes that lets the sperm penetrate the egg's coat. The midpiece is packed with mitochondria that power the tail, a whiplike flagellum. Sperm are made in the seminiferous tubules of the testis and mature in the epididymis.
How to spot them
- âļTadpole-like cell with an oval head, a short thick neck and midpiece, and a long thin tail
- âļHead only about 5 micrometres long, mostly nucleus, with a cap-like acrosome over the front
- âļMidpiece packed with spirally arranged mitochondria
- âļTail is a flagellum with a 9+2 arrangement of microtubules
- âļAlmost no cytoplasm â the smallest cell in the human body by volume
What to know
The cell that carries either an X or a Y chromosome, deciding the sex of a child
Sperm cell â the father's chromosome determines the sex.
The cap on its head releases enzymes that help it burrow through the coat of the egg
Sperm cell â the acrosome reaction.
Between 100 and 300 million are made every day in coiled tubules, taking about ten weeks from start to finish
Sperm cell â spermatogenesis in the seminiferous tubules.
First seen through the microscope in 1677 by Antonie van Leeuwenhoek and his assistant Johan Ham, who called them 'animalcules' (1677)
Sperm cell â early microscopy of semen.
It matures and gains the power of movement while stored in a tightly coiled tube behind the testis
Sperm cell â the epididymis.
The smallest cell in the body by volume, whose counterpart is the largest
Sperm cell â the egg is the largest.
Key ideas
- Once inside the female tract a sperm becomes capable of fertilising in a process called capacitation. At the egg it undergoes the acrosome reaction, releasing enzymes, and its membrane fuses with the egg's.
- Only the head enters the egg. The tail and midpiece mitochondria are broken down, so mitochondrial DNA is inherited from the mother.
Quick-fire facts
- âĒTotal length is about 50â60 micrometres; the head is only about 5 micrometres long
- âĒIt carries 23 chromosomes â half the normal number â which combine with the egg's 23 to make 46
- âĒAround 100â300 million are made daily (OpenStax); the process takes roughly 64â74 days
- âĒSpeeds of a few millimetres a minute are typical for progressive swimming
- âĒSperm can survive in the female reproductive tract for several days
- âĒWHO reference values place a normal concentration at about 16 million or more per millilitre of semen (lower fifth percentile)
- âĒFertilisation normally takes place in the ampulla of the uterine tube
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