Vitelline membrane 5169740 216086768 2008-05-31T00:41:29Z CmdrObot 1079367 Wikipedia URL→wikilink {{Infobox Embryology | Name = {{PAGENAME}} | Latin = m. vitellina | GraySubject = 5 | GrayPage = 45 | Image = | Caption = | Image2 = | Caption2 = | System = | CarnegieStage = | Days = | Precursor = | GivesRiseTo = | MeshName = Vitelline+membrane | MeshNumber = A16.631.886 | DorlandsPre = m_08 | DorlandsSuf = 12523303 | }} 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]] {{developmental-biology-stub}} {{Gray's}} {{Embryology}}[[Category:Embryology]]