Psychology Wiki


Revision as of 17:39, October 6, 2011 by Dr Joe Kiff (Talk | contribs)

34,191pages on
this wiki



Latin spermiusmatro
Gray's subject #258 1243
MeSH A05.360.490.890
Diagram of a human spermatozoon

A spermatozoon (alternate spellings spermatozoan, spermatozoön; plural spermatozoa) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. (A non-motile sperm cell is called a spermatium.) A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) The term spermatozoon comes from the ancient Greek word σπέρμα (seed) and ζῷον (living being).

Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring. In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing a Y-chromosome will lead to a male (XY) offspring, while one bearing an X-chromosome will lead to a female (XX) offspring (the ovum always provides an X-chromosome). Sperm cells were first observed by Anton van Leeuwenhoek in 1677.[1]

Mammalian spermatozoan structure, function, and size



The human sperm cell is the reproductive cell in males and will only survive in warm environments, once leaving the body the sperm's survival is reduced and may cause the cell to die, decreasing the sperm quality. Sperm cells come in two types, "female" and "male". Sperm cells that give rise to female (XX) offspring after fertilization differ in that they carry an X-chromosome, while sperm cells that give rise to male (XY) offspring carry a Y-chromosome.

In male humans, sperm cells consists of a head 5 µm by 3 µm and a tail 41 µm long. The tail flagellates, which propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone.[2] Semen has an alkaline nature, and they do not reach full motility (hypermotility) until they reach the vagina where the alkaline pH is neutralized by acidic vaginal fluids. This gradual process takes 20–30 minutes. In this time, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Just as they become hypermotile, fibrinolysin from the prostate dissolves the clot, allowing the sperm to progress optimally.


The specimen contributes with DNA/chromatin, a centriole and perhaps also an oocyte-activating factor (OAF).[4] It may also contribute with paternal Messenger RNA (mRNA), also contributing to embryonic development.[4]

Avoidance of immune system response

Glycoprotein molecules on the surface of sperm cells are recognized by all human immune systems, and interpreted as a signal that the cell should not be rejected. The male immune system might otherwise attack sperm whilst in the testes, and the female immune system would attack sperm in the reproductive tract. The specific glycoproteins coating sperm cells are also utilized by some cancerous and bacterial cells, some parasitic worms, and HIV-infected white blood cells, thereby avoiding an immune response from the host organism.[5]

The blood-testis barrier, maintained by the tight junctions between the Sertoli cells of the seminiferous tubules, prevents communication between the forming spermatozoa and the blood vessels within the interstitial space. This gives the forming spermatozoa an immunological advantage and thus prevents them from eliciting an immune response. The blood-testis barrier is also important in preventing toxic substances from disrupting spermatogenesis.

Spermatozoa in other organisms

File:Plant sperm.png
See also: Sperm


Fertilization relies on spermatozoa for most sexually reproductive animals.

The fruit fly has the largest known spermatozoon relative to its size.[6] Drosophila melanogaster produces sperm that can be up to 1.8 cm[7] in size. The incredibly long tail is thought to block other sperm from entering the egg. The entire sperm, tail included, gets incorporated into the oocyte cytoplasm.[8]



Spermatozoa production in mammals

Main article: Spermatogenesis


Spermatozoa activation

Main article: Acrosome reaction
File:Acrosome reaction diagram en.svg







See also


  1. includeonly>"Timeline: Assisted reproduction and birth control", CBC News. Retrieved on 2006-04-06.
  3. Ward WS, Coffey DS (1991). DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells. Biol. Reprod. 44 (4): 569–74.
  5. includeonly>"Sperm clue to 'disease immunity'", BBC News, 2007-12-17.
  8. Gilbert, Scott F., Developmental Biology, Eighth Edition. 2006. Sinauer Associates, pp. 254
  9. Moore, Harry et al., Exceptional sperm cooperation in Wood Mouse.Nature 418, 174-177 (2002)
  10. Gnessi L, Fabbri A, Silvestroni L, Moretti C, Fraioli F, Pert CB, Isidori A. (1986). Evidence for the presence of specific receptors for N-formyl chemotactic peptides on human spermatozoa.. J Clin Endocrinol Metab 63 (4): 841–6.

External links

Template:Commons cat


Around Wikia's network

Random Wiki