|
[[Image:Faro de La Serena.jpg|thumb|258px|Faro of The City]]
{{Infobox Anatomy |
[[Image:La Serena-Coquimbo-02.jpg|thumb|258px|The city of La Serena with the port city of [[Coquimbo, Chile|Coquimbo]] in the background]]
Name = {{PAGENAME}} |
[[Image:Plaza de Armas - La Serena.jpg|thumb|250px|Plaza de Armas]]
Latin = |
GraySubject = 258 |
GrayPage = 1243 |
Image = Sperm-egg.jpg |
Caption = A sperm cell attempts to penetrate an [[ovum]] coat to [[Fertilisation|fertilize]] it. |
Image2 = Complete diagram of a human spermatozoa.svg |
Width = 350 |
Caption2 = Diagram of a human spermatozoon |
System = |
MeshName = Spermatozoa |
MeshNumber = A05.360.490.890 |
}}
A '''spermatozoon''' or '''spermatozoan''' (''pl.'' '''spermatozoa'''), from the [[ancient Greek]] σπέρμα (seed) and {{unicode|ζῷον}} (living being) and more commonly known as a '''sperm cell''', is the [[ploidy|haploid]] [[cell (biology)|cell]] that is the male [[gamete]]. It [[Fertilization|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]].
Sperm cells contribute half of the [[gene|genetic information]] to the [[diploid]] offspring. In mammals, the [[sex]] of the offspring is determined by the sperm cells: 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 a student of [[Anton van Leeuwenhoek|Antoni van Leeuwenhoek]] in [[1677]].<ref>{{cite web|url=http://www.cbc.ca/news/background/genetics_reproduction/timeline.html|title=Timeline: Assisted reproduction and birth control|accessdate=2006-04-06}}</ref>
'''La Serena''' ("the serene one") is the second oldest city in [[Chile]]. The city, located 471 km north of [[Santiago, Chile|Santiago]], has a population of 147,815, according to the 2002 census. There are also 12,333 inhabitants of the immediately surrounding countryside. It is one of the fastest-growing areas of Chile, witnessing a population increase of 32.6% between [[1992]] and [[2002]].
==Spermatozoan structure and size==
===Humans===
The human sperm cell is the reproductive cell in males. Sperm cells come in two types; "male" and "female." The females differ in that they carry an X chromosome, while the male sperm carry a Y chromosome. The female sperm cell also differs phenotypically in that it has a larger head in comparison to the male sperm cell.
====Males====
In male humans, sperm cells consists of a head 5 [[micrometre|µm]] by 3 µm and a tail 50 µm long. The [[Reynolds number]] associated with spermatozoa is in the order of 1{{e|-2}}, so it is known that the spermatozoa exhibits [[laminar flow]]. Spermatozoan stream lines are straight and parallel. The tail [[flagellate]]s, which propels the sperm cell (at about 1-3 mm/minute in humans) by whipping in an elliptical cone.
<ref>Sumio Ishijima, Shigeru Oshio, Hideo Mohri, "''Flagellar movement of human spermatozoa''", Gamete research, 1986, vol. 13, no3, pp. 185-197 (27 ref.) [http://www3.interscience.wiley.com/cgi-bin/abstract/109926914/ABSTRACT?CRETRY=1&SRETRY=0]</ref>. The cell is characterized by a minimum of [[cytoplasm]]. During fertilization, the sperm's [[mitochondria]] are destroyed by the egg cell, and this means only the mother is able to
provide the baby's mitochondria and [[mitochondrial DNA]], which have an important application in tracing maternal [[ancestry]]. However it has been recently discovered that mitochondrial DNA can be recombinant
<ref>Marilena D'Aurelio et al., "'Heterologous mitochondrial DNA recombination in human cells'", Human Molecular Genetics 2004 13(24):3171-3179; doi:10.1093/hmg/ddh326 [http://hmg.oxfordjournals.org/cgi/content/abstract/13/24/3171]</ref>.
It was first founded by Spaniard Captain [[Juan Bohón]] in [[September 4]] [[1544]] on the orders of [[Pedro de Valdivia]] in order to provide a sea link between Santiago and [[Lima]]. In [[1549]] the town was totally destroyed by local Indians and re-founded the same year by Captain Francisco de Aguirre in a safer ___location. The town has retained its historic architecture and this, along with a selection of beaches (known as Avenida del Mar, "Sea Avenue"), has caused the city to become a significant tourist centre, attracting many foreigners (most of them Argentines from San Juan and Mendoza provinces) during January, and later Santiago residents fleeing February heat.
===In other organisms===
The [[fruit fly]]<sup>[http://www.livescience.com/animalworld/060616_big_sperm.html]</sup> has the largest known spermatazoon relative to its size.
Its traditional architecture consists of a series of housing and public buildings, of late 19th-century vintage, built with wood from the [[USA|US]] state of [[Oregon]] brought to Chile as counterweight in sailing vessels coming to [[Coquimbo]], the nearby port, to load copper and other minerals for transport back to the US. This Oregon pine and the use of [[adobe]] create the genuine image of the city.
{{section-stub}}
There is also a number of remarkable and valuable small churches built of sedimentary stone quarried 5 km to the north of the [[Elqui River]], having a characteristic color and texture formed by myriad small shells. These churches are all roughly 350 years old and have undergone restoration to varying degrees, bringing them back to their original form. San Francisco, San Agustín, Santo Domingo are the names of a few of them.
==Sperm in other organisms==
The Cathedral, built from the same stone, dates from the 19th century. It must be said that although it lacks the same historical value as the older churches, this is a stone building in a country prone to seismic activity, and has survived various earthquakes. Indeed, during centuries of existence, there is almost no visible damage. All of these churches, along with others of minor importance, provide a unique urban landscape, an image for the city, giving it the nickname "''The City of Churches''."
===Animals===
Fertilization relies on sperm cells for most, if not all, sexually reproductive animals.
A few of the major sectors are: El Centro ("downtown"), Peñuelas (actually a suburb between La Serena and its sister city [[Coquimbo]]), San Joaquín (neighborhood on a hill overlooking the ocean), La Florida, Las Compañías ("the companies"), Cerro Grande ("big hill"), La Antena and the new El Milagro ("the miracle") development.
[[Sea urchins]] such as ''Arbacia punctulata''—are the workhorses of sperm research, because they spawn large numbers of sperm
into the sea, making them well-suited as model organisms for research experiments.
===Plants===
The [[gametophyte]]s of [[bryophyte]]s, [[fern]]s and some [[gymnosperm]]s produce motile sperm, contrary to [[pollen]]s or other more complex arrangement of gametophytes, employed in most gymnosperms and all [[angiosperm]]s. This renders sexual reproduction in the absence of [[water]] impossible, since water is a necessary medium for sperm and egg to meet.
{{section-stub}}
== Genetic odds ==
It is clear that the odds of the sexes can be manipulated in differing species. For example, temperature affects the sex of offspring in some [[reptile]]s, such as [[crocodile]]s and [[turtle]]s. Cool incubation temperature produces male offspring while warm temperature produces female offspring. However, sex determination in most mammals, as in humans, is chromosomal.
== Sperm cell production ==
{{Main|Spermatogenesis}}
Spermatozoa are produced in the [[seminiferous tubule]]s of the [[testes]] in a process called spermatogenesis. Round cells called [[spermatogonia]] divide and differentiate eventually to become spermatozoa. During [[copulation]] the [[cloaca]] or [[vagina]] gets [[insemination|inseminat]]ed, and then the spermatozoa move through [[chemotaxis]] to the ovum inside a [[Fallopian tube]] or the [[uterus]].
== The acrosome reaction ==
[[Image:Acrosome reaction diagram.svg|thumb|440px|left|Acrosome reaction on a Sea Urchin cell]]
Mammalian sperm cells become even more active when they approach an egg cell. They swim faster and their tail movements become more forceful and erratic. This behaviour is called "hyperactivation."
A recent discovery links hyperactivation to a sudden influx of calcium ion into the tails. The whip-like tail (flagellum) of the sperm is studded with [[ion channel]]s formed by proteins called [[CatSper]]. These channels are selective, allowing only calcium ion to pass. The opening of CatSper
channels is responsible for the influx of calcium. The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment. Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization.
The first barrier to sperm is made up of so-called cumulus cells embedded in a gel-like substance made primarily of hyaluronic acid. The cumulus cells develop in the ovary with the egg and support it as it grows.
The second barrier coating the [[oocyte]] is a thick shell formed by glycoproteins called the [[zona pellucida]]. One of the proteins that make up the zona pellucida binds to a partner molecule on the sperm. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. There is some evidence that this binding is what triggers the [[acrosome]] to release the enzymes that allow the sperm to fuse with the egg.
When a sperm cell reaches the egg the acrosome releases its enzymes. These enzymes weaken the shell, allowing the sperm cell to penetrate it and reach the plasma membrane of the egg. Part of the sperm's cell membrane then [[fertilization|fuses]] with the egg cell's membrane, and the contents of the head sink into the egg.
Upon penetration, the oocyte is said to have become activated. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a [[zygote]]. In order to prevent [[Polyspermy|polyspermy]] and minimise the possibility of producing a [[Triploidy|triploid]] zygote, several changes to the egg's cell membranes renders them impenetrable shortly after the first sperm enters the egg.
==References==
<references />
==External links==
* [http://www.andrologysocietyuserena.comcl/resources/handbook.asp TheUniversity Handbookof ofLa AndrologySerena]
* [http://www.livesciencewunderground.com/humanbiologyglobal/060208_hyper_spermstations/85488.html/ Spermweather hyperactivityforecast]
* [http://www.irishhealthvisit-chile.comorg/?level=4&id=9863norte/h21.phtml Chilean tourist Womensite couldfor makeLa spermSerena]
*[http://www.intimahinatravel.cl travel agency]
* [http://news.bbc.co.uk/2/hi/health/4529152.stm Slower conception 'leads to boys']
{{coor title dm|29|54|S|71|15|W|region:CL_type:city}}
* [http://www.fertilityformen.com/info.php Photos of sperm under a microscope]
[[Category:Cities in Chile]]
{{Male reproductive system}}
[[Category:Communes of Chile]]
[[Category:Capitals of Chilean regions]]
[[Category:Settlements established in 1544]]
[[Category:Cities and towns in Coquimbo Region]]
[[de:La Serena]]
[[Category:Male reproductive system]]
[[es:La Serena (Chile)]]
[[Category:Germ cells]]
[[Categoryfr:AndrologyLa Serena]]
[[it:La Serena]]
[[ar:حيوانات منوية]]
[[afnl:SemenLa Serena]]
[[no:La Serena]]
[[bg:Сперматозоид]]
[[bspl:SpermatozoidLa Serena]]
[[capt:EspermatozoideLa Serena]]
[[cssl:SpermieLa Serena]]
[[dafi:SædcelleLa Serena]]
[[desv:SpermiumLa Serena]]
[[es:Espermatozoide]]
[[fr:Spermatozoïde]]
[[he:זרע (היסטולוגיה)]]
[[hr:Spermij]]
[[id:Spermatozoid]]
[[io:Spermatozoido]]
[[it:Spermatozoo]]
[[ja:精子]]
[[lt:Spermatozoidas]]
[[mk:Сперматозоид]]
[[nl:Zaadcel]]
[[no:Spermie]]
[[pl:Plemnik]]
[[pt:Espermatozóide]]
[[ru:Сперматозоид]]
[[simple:Sperm]]
[[su:Spérma]]
[[fi:Siittiö]]
[[sv:Spermie]]
[[tr:sperm]]
[[yi:זרע]]
[[zh:精子]]
| 