Sperm
2324040
225839121
2008-07-15T17:15:11Z
J.delanoy
2372780
Reverted edits by [[Special:Contributions/88.104.97.59|88.104.97.59]] to last version by Excirial (using [[WP:HG|Huggle]])
[[Image:sperm.svg|thumb|Different types of sperm cells: A) [[spermatozoon]] ([[Motility|motile]]), B) spermatium (non-motile), C) fertilization tube with sperm nuclei]]
The term '''sperm''' is derived from the Greek word (σπέρμα) ''sperma'' (meaning "seed") and refers to the male reproductive cells. '''Sperm cells''' are the smaller [[gamete]]s involved in [[fertilization]] in [[anisogamy]] and [[oogamy]]. In these types of [[sexual reproduction]], there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell. The human sperm cell is a [[haploid]], so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a [[diploid]] cell. A uniflagellar sperm cell that is [[ Motility| motile]] is also referred to as '''[[spermatozoon]]''', whereas a non-motile sperm cell is referred to as '''spermatium'''. Sperm cells cannot divide and have a limited life span, but they can fuse with [[Ovum|egg cells]] during fertilization to form a [[Totipotency|totipotent]] [[zygote]] with the potential to develop into a new organism. Mammalian sperm cells can live for up to 3 days inside the female unless it is exposed to air or is mixed with another liquid.{{fact|date=April 2008}}
The spermatozoa of animals are produced through [[spermatogenesis]] inside the male [[gonad]]s ([[testicle]]s) through [[meiosis]]. Sperm cells in algal and many plant [[gametophyte]]s are produced in male [[Gametangium|gametangia]] ([[Antheridium|antheridia]]) through [[mitosis]]. In [[flowering plant]]s, sperm nuclei are produced inside [[pollen]].
== Anatomy ==
The sperm cell consists of a head, a midpiece and a tail. The head is the [[nucleus]] with densely coiled cromatinfibres, surrounded anteriorly by an [[acrosome]], which contains enzymes used for penetrating the female egg. The midpiece has a central filamentous core with many mitochondria spiralled around it, used for ATP production for the journey through the female [[cervix]], [[uterus]] and [[uterine tubes]]. The tail or "[[flagellum]]" executes the lashing movements that propel the spermatocyte, and it consists of microtubules in an extension of the cell membrane.
==Motile sperm cells==
[[Image:Plant sperm.png|thumb|Motile sperm cells of algae and seedless plants.<ref name="Raven">{{cite book | last = Raven | first = Peter H. | coauthors = Ray F. Evert, Susan E. Eichhorn | title = Biology of Plants, 7th Edition | publisher = W.H. Freeman and Company Publishers | date = 2005 | location = New York | pages = | isbn = 0-7167-1007-2}}</ref>]]
Motile sperm cells typically move via [[Flagellum|flagella]] and require water in order to swim toward the egg for fertilization. The uniflagellated sperm cells (with one flagellum) produced in most [[animal]]s are referred to as '''[[Spermatozoon|spermatozoa]]''', and are known to vary in size.
Motile sperm are also produced by many [[protist]]s and the [[gametophyte]]s of [[bryophyte]]s, [[fern]]s and some [[gymnosperm]]s such as [[cycad]]s and [[ginkgo]]. The sperm cells are the only flagellated cells in the life cycle of these plants. In many ferns and [[lycophyte]]s, they are multi-flagellated (carrying more than one flagellum).<ref name="Raven"/>
In [[nematode]]s, the sperm cells are [[amoeboid]] and crawl, rather than swim, towards the egg cell.<ref name="Bottino">{{cite journal |author=Bottino D, Mogilner A, Roberts T, Stewart M, Oster G |title=How nematode sperm crawl |journal=J. Cell. Sci. |volume=115 |issue=Pt 2 |pages=367–84 |year=2002 |pmid=11839788 |doi=}}</ref>
== Non-motile sperm cells ==
Non-motile sperm cells called '''spermatia''' lack flagella and therefore cannot swim. Spermatia are produced in a [[Gametangium|spermatangium]].<ref name="Raven"/>
Because spermatia cannot swim,they depend on their environment to carry them to the egg cell. Some [[red alga]]e, such as ''[[Polysiphonia]]'', produce non-motile spermatia that are spread by water currents after their release.<ref name="Raven"/> The spermatia of [[Rust (fungus)|rust fungi]] are covered with a sticky substance. They are produced in flask-shaped structures containing [[nectar]], which attract [[Fly|flies]] that transfer the spermatia to nearby [[hyphae]] for fertilization in a mechanism similar to [[insect pollination]] in [[flowering plant]]s.<ref name="Sumbali">{{cite book | last = Sumbali| first = Geeta | coauthors = | title = The Fungi | publisher = Alpha Science Int'l Ltd. | date = 2005 | location = | pages = | isbn = 1842651536}}</ref>
Fungal spermatia (also called pycnidiospores) may be confused with [[conidium|conidia]]. Conidia are [[spore]]s that germinate independently of fertilization, whereas spermatia are [[gamete]]s that are required for fertilization. In some fungi, such as ''[[Neurospora crassa]]'', spermatia are identical with microconidia as they can perform both functions of fertilization as well as giving rise to new organisms without fertilization.<ref name="Maheshwari">{{cite journal |author=Maheshwari R |title=Microconidia of Neurospora crassa |journal=Fungal Genet. Biol. |volume=26 |issue=1 |pages=1–18 |year=1999 |pmid=10072316 |doi=10.1006/fgbi.1998.1103}}</ref>
==Sperm nuclei==
In many [[land plant]]s, including most gymnosperms and all [[angiosperm]]s, the male [[gametophyte]]s ([[Pollen|pollen grains]]) are the primary mode of [[biological dispersal|dispersal]], for example via wind or insect [[pollination]], eliminating the need for water to bridge the gap between male and female. Each pollen grain contains a spermatogenous (generative) cell. Once the pollen lands on the [[Stigma (flower)|stigma]] of a receptive flower, it germinates and starts growing a [[pollen tube]] through the [[carpel]]. Before the tube reaches the [[ovule]], the nucleus of the generative cell in the pollen grain divides and gives rise to two sperm nuclei which are then discharged through the tube into the [[ovule]] for fertilization.<ref name="Raven"/>
In some [[protist]]s, fertilization also involves sperm [[Cell nucleus|nuclei]], rather than cells, migrating toward the egg cell through a fertilization tube. [[Oomycete]]s form sperm nuclei in a [[syncytium|syncytical]] [[antheridium]] surrounding the egg cells. The sperm nuclei reach the eggs through fertilization tubes, similar to the pollen tube mechanism in plants.<ref name="Raven"/>
==Sperm quality==
{{main|Semen quality}}
A study by the [[University of California]] has suggested that [[folate]] may protect sperm cells from [[aneuploidy]].[http://news.bbc.co.uk/2/hi/health/7303375.stm]
==Market==
On the global market, [[Denmark]] has a well developed system of sperm export. This success mainly comes from the reputation of Danish sperm donors for being of high quality and, in contrast with the law in the other Nordic countries, gives donors the choice to remain anonymous to the receiving couple.<ref name=ncbio> [http://www.ncbio.org/NcBioBurrell.pdf Assisted Reproduction in the Nordic Countries] ncbio.org </ref> More than 50 countries worldwide are importers, including Paraguay, the US, Kenya and Hong Kong.<ref name=ncbio/>
==See also==
*[[Ejaculation]]
*[[Female sperm]]
*[[Polyspermy]]
*[[Semen]]
*[[Sperm competition]]
*[[Sperm donation]]
==References==
{{Reflist}}
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{{succession box|title=[[Stages of human development]] |before=None|after=[[Zygote]]|years=Sperm}}
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[[Category:Reproduction]]
[[Category:Reproductive system]]
[[Category:Male reproductive system]]
[[Category:Germ cells]]
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