🌱 Fertilization

Fertilization Mechanisms

• The primary block to prevent polyspermy is the fast block, which is the depolarization of the egg's plasma membrane.

Acrosome Reaction

• The acrosome reaction in sperm is triggered by the binding of sperm to the zona pellucida, specifically to the ZP3 protein.

Embryonic Development

• The fertilization of the egg by a sperm initiates embryonic development in the fertilized egg.

ZP3 Function

• ZP3, a protein in the zona pellucida, serves as a receptor for sperm binding, initiating the acrosome reaction and subsequently, fertilization.

Prevention of Polyspermy

• The fertilization of the egg triggers a change in the egg cell surface, preventing the entry of other sperm and ensuring monospermy during fertilization.

Capacitation and Activation: Sperm undergoes activation through the acrosome reaction after capacitation. Prevention of Polyspermy:

Primary (Fast) Block: Depolarization of the plasma membrane. Secondary (Slow) Block: Cortical reaction involving Ca2+ increase, exocytosis of granules, and modification of zona pellucida.

Zona Pellucida (ZP): Glycoproteins: ZP1, ZP2, ZP3. ZP3 interaction with sperm triggers acrosomal reaction.

Fertilization Process: Sperm-egg interaction increases cytosolic Ca2+. Ca2+ wave prevents entry of other sperm and initiates embryonic development.