Sperm
Male reproductive cell that fuses with egg to form a zygote.
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction, where it is the smaller cell compared to the female egg. Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring and are essential for fertilization, leading to the development of a new organism.
- type
- Male reproductive cell (gamete)
- function
- Deliver male pronucleus and centrioles to ovum during fertilization
- size
- Head approx. 5.1 by 3.1 μm; tail approx. 50 μm
- motility
- 1 to 3 mm per minute
- chromosome count
- Haploid, 23 chromosomes in humans
- formation process
- Spermatogenesis in seminiferous tubules of testicles (amniotes)
- lifespan
- Limited; cannot divide; degrades after leaving warm environment
Lore & Background
Sperm cells have an olfactory guidance mechanism and must undergo capacitation before penetrating the ovum. During fertilization, the sperm provides an oocyte-activating factor, the haploid paternal genome, and a centriole. The word 'sperm' is derived from the Greek word σπέρμα, sperma, meaning 'seed'.
Reader's Guide
Sperm is fundamental to sexual reproduction in anisogamous organisms, contributing half the nuclear genetic material to offspring. In humans, sperm function is to reach the ovum and fuse with it, delivering the male pronucleus and centrioles. The study of sperm includes understanding spermatogenesis, the role of the acrosome in egg penetration, and the mechanisms of motility via the flagellum. Sperm are vulnerable to oxidative DNA damage, and exposure to hazards like tobacco smoking or benzene can increase aneuploidy. The blood-testis barrier protects developing sperm from immune attack, and glycoproteins on sperm surfaces signal the female immune system not to reject them. Sperm's limited lifespan and need for a warm environment affect fertility. The evolution of sperm from isogamy is studied through mathematical models due to lack of fossil evidence, with a hypothesis that sperm evolved rapidly, though direct evidence is absent. Sperm's role in fertilization and its unique cellular structures make it a key subject in reproductive biology.
Did You Know?
- Sperm cells contribute approximately half of the nuclear genetic information to offspring, but typically do not contribute mitochondrial DNA.
- The human sperm head is disc-shaped and approximately 5.1 by 3.1 μm.
- Sperm cells cannot divide and have a limited lifespan; they degrade after leaving the warm environment of the body.
- The word 'sperm' comes from the Greek word σπέρμα, sperma, meaning 'seed'.
More in Reproductive Biology 1-22
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