Vitelline membrane
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{{Infobox Embryology |
Name = {{PAGENAME}} |
Latin = m. vitellina |
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GrayPage = 45 |
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MeshName = Vitelline+membrane |
MeshNumber = A16.631.886 |
DorlandsPre = m_08 |
DorlandsSuf = 12523303 |
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The vitelline membrane is a structure directly adjacent to the outer surface of the [[plasma membrane]] of an [[ovum]]. It is composed mostly of protein fibers, with protein receptors needed for sperm binding, binding to sperm plasma membrane receptors. The species-specificity between these receptors contributes to prevention of breeding between different species.
It is called [[zona pellucida]] in [[mammal]]s.
As soon as the [[spermatozoon]] fuses with the [[ovum]], [[signal transduction]] occurs, resulting in an increase of cytoplasmic calcium ions. This itself triggers the [[cortical reaction]], which results in depositing several substances onto the vitelline membrane through exocytosis of the cortical granules, transforming it into a hard layer called the “fertilization membrane”, which serves as a barrier inaccessible to other spermatozoa. This phenomenon is the [[Egg activation#Fast_and_slow_block_to_polyspermy|slow block to polyspermy]].
==See also==
* [[Zona pellucida]]
* [[Egg activation]]
* [[Cortical reaction]]
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{{Embryology}}[[Category:Embryology]]