CorticalgranulenReaktionen

CorticalgranulenReaktionen, a German term, translates to "cortical granule reactions" in English. This phenomenon is a crucial event in the fertilization of eggs in many animal species, particularly in mammals. Following the fusion of a sperm with the egg's plasma membrane, a wave of calcium ions is released from intracellular stores within the egg. This calcium surge triggers the cortical granules, which are membrane-bound organelles located just beneath the egg's plasma membrane, to fuse with the plasma membrane and release their contents into the perivitelline space.

The primary function of the released cortical granule contents is to establish the "block to polyspermy," a mechanism that prevents multiple sperm from fertilizing the egg. These released substances modify the egg's outer layers, the zona pellucida in mammals, making it impermeable to further sperm penetration. This modification can involve enzymatic degradation of zona pellucida proteins or alterations in the physical properties of the extracellular matrix. Without a functional cortical granule reaction, the fertilized egg would be polyspermic, leading to developmental abnormalities and typically non-viable embryos. The precise composition and mechanism of action of cortical granule contents can vary between species.