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The human [[sperm cell]] is the [[Gamete|reproductive cell]] in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby decreasing the total [[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.<ref>{{cite book |last1=Scheinfeld |first1=Amram |title=You and Heredity |date=1939 |publisher=Frederick A. Stokes Company |location=New York |pages=39}}</ref> |
The human [[sperm cell]] is the [[Gamete|reproductive cell]] in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby decreasing the total [[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.<ref>{{cite book |last1=Scheinfeld |first1=Amram |title=You and Heredity |date=1939 |publisher=Frederick A. Stokes Company |location=New York |pages=39}}</ref> |
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A human sperm cell consists of a flat, disc shaped head 5.1 [[micrometre| |
A human sperm cell consists of a flat, disc shaped head 5.1 [[micrometre|µm]] by 3.1 µm and a tail known as a [[Flagellum#Eukaryotic|flagellum]] 50 µm long.<ref>{{cite journal |last1=Smith |first1=D. J. |last2=Gaffney |first2=E. A. |last3=Blake |first3=J. R. |last4=Kirkman-Brown |first4=J. C. |title=Human sperm accumulation near surfaces: a simulation study |journal=Journal of Fluid Mechanics |date=25 February 2009 |volume=621 |pages=289–320 |doi=10.1017/S0022112008004953 |bibcode=2009JFM...621..289S |s2cid=3942426 |url=http://pure-oai.bham.ac.uk/ws/files/17448418/Smith2009_S0022112008004953a.pdf |access-date=10 September 2021 |archive-date=27 January 2022 |archive-url=https://web.archive.org/web/20220127073249/http://pure-oai.bham.ac.uk/ws/files/17448418/Smith2009_S0022112008004953a.pdf |url-status=live }}</ref> The flagellum propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone.<ref>{{cite journal | last1 = Ishijima | first1 = Sumio | last2 = Oshio | first2 = Shigeru | last3 = Mohri | first3 = Hideo | year = 1986 | title = ''Flagellar movement of human spermatozoa'' | journal = Gamete Research | volume = 13 | issue = 3| pages = 185–197 | doi = 10.1002/mrd.1120130302 }}</ref> Sperm have an olfactory [[Olfactory receptor#Expression|guidance mechanism]], and after reaching the [[fallopian tube]]s, must undergo a period of [[capacitation]] before penetration of the ovum.<ref>{{cite journal |last1=Eisenbach |first1=Michael |last2=Giojalas |first2=Laura C. |title=Sperm guidance in mammals — an unpaved road to the egg |journal=Nature Reviews Molecular Cell Biology |date=April 2006 |volume=7 |issue=4 |pages=276–285 |doi=10.1038/nrm1893 |pmid=16607290 |hdl=11336/57585 |s2cid=32567894 |hdl-access=free }}</ref> |
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'''Head:''' It has a compact nucleus with only chromatic substance and is surrounded by only a thin rim of cytoplasm. Above the nucleus lies a cap-like structure called the [[acrosome]], formed by modification of the Golgi body, which secretes the enzyme '''spermlysin''' (''hyaluronidase, corona-penetrating enzyme, zona lysin,'' or ''acrosin''), that is necessary for fertilization. As the spermatozoon approaches the egg, it undergoes the [[acrosome reaction]] in which the membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head, exposing the contents of the acrosome.<ref>{{cite journal |last1=del Río |first1=María José |last2=Godoy |first2=Ana |last3=Toro |first3=Alejandra |last4=Orellana |first4=Renán |last5=Cortés |first5=Manuel E. |last6=Moreno |first6=Ricardo D. |last7=Vigil |first7=Pilar |title=La reacción acrosómica del espermatozoide: avances recientes |journal=Revista Internacional de Andrología |date=October 2007 |volume=5 |issue=4 |pages=368–373 |doi=10.1016/S1698-031X(07)74086-4 }}</ref> |
'''Head:''' It has a compact nucleus with only chromatic substance and is surrounded by only a thin rim of cytoplasm. Above the nucleus lies a cap-like structure called the [[acrosome]], formed by modification of the Golgi body, which secretes the enzyme '''spermlysin''' (''hyaluronidase, corona-penetrating enzyme, zona lysin,'' or ''acrosin''), that is necessary for fertilization. As the spermatozoon approaches the egg, it undergoes the [[acrosome reaction]] in which the membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head, exposing the contents of the acrosome.<ref>{{cite journal |last1=del Río |first1=María José |last2=Godoy |first2=Ana |last3=Toro |first3=Alejandra |last4=Orellana |first4=Renán |last5=Cortés |first5=Manuel E. |last6=Moreno |first6=Ricardo D. |last7=Vigil |first7=Pilar |title=La reacción acrosómica del espermatozoide: avances recientes |journal=Revista Internacional de Andrología |date=October 2007 |volume=5 |issue=4 |pages=368–373 |doi=10.1016/S1698-031X(07)74086-4 }}</ref> |
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'''Neck:''' It is the smallest part (.03 |
'''Neck:''' It is the smallest part (.03 µm), and has a proximal [[centriole]] parallel to the base of the nucleus and distal [[centriole]] perpendicular to the previous one. The proximal centriole is present also in the mature spermatozoon; the distal centriole disappears after axoneme assembly. The proximal centriole enters into the egg during fertilisation and starts the first cleavage division of the egg, which has no centriole. The distal centriole gives rise to the axial filament which forms the tail and has a (9+2) arrangement. A transitory membrane called the ''Manchette'' lies in the middle piece. |
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'''Middle piece:''' It has 10–14 spirals of mitochondria surrounding the axial filament in the cytoplasm. It provides motility, and hence is called the powerhouse of the sperm. It also has a ring centriole (annulus) that form a diffusion barrier between the middle piece and the principal piece and serve as a stabilizing structure for tail rigidity.<ref>{{Cite web|url=https://www.yeastgenome.org/go/GO:0097227|title=sperm annulus {{!}} SGD|website=www.yeastgenome.org|access-date=2019-02-22|archive-date=2019-02-22|archive-url=https://web.archive.org/web/20190222152105/https://www.yeastgenome.org/go/GO:0097227|url-status=live}}</ref> |
'''Middle piece:''' It has 10–14 spirals of mitochondria surrounding the axial filament in the cytoplasm. It provides motility, and hence is called the powerhouse of the sperm. It also has a ring centriole (annulus) that form a diffusion barrier between the middle piece and the principal piece and serve as a stabilizing structure for tail rigidity.<ref>{{Cite web|url=https://www.yeastgenome.org/go/GO:0097227|title=sperm annulus {{!}} SGD|website=www.yeastgenome.org|access-date=2019-02-22|archive-date=2019-02-22|archive-url=https://web.archive.org/web/20190222152105/https://www.yeastgenome.org/go/GO:0097227|url-status=live}}</ref> |
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'''Tail:''' The flagellum is the longest part (50 |
'''Tail:''' The flagellum is the longest part (50 µm), having an axial filament surrounded by cytoplasm and plasma membrane, but at the posterior end the axial filament is naked. The flagellum gives movement to the cell. |
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[[Semen]] has an alkaline nature and the spermatozoa 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. During this period, [[fibrinogen]] from the [[seminal vesicle]]s forms a clot, securing and protecting the sperm. Just as they become hypermotile, [[fibrinolysin]] from the [[prostate gland]] dissolves the clot, allowing the sperm to progress optimally. |
[[Semen]] has an alkaline nature and the spermatozoa 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. During this period, [[fibrinogen]] from the [[seminal vesicle]]s forms a clot, securing and protecting the sperm. Just as they become hypermotile, [[fibrinolysin]] from the [[prostate gland]] dissolves the clot, allowing the sperm to progress optimally. |
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