4
Question
A reaction which helps in hardening the zona pellucida to ensure block to polyspermy is _________ .
A reaction which helps in hardening the zona pellucida to ensure block to polyspermy is _________ .
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Solution
The correct option is B cortical reaction
The fusion of sperm with egg in human beings is preceded by the following steps.
1. Capacitation: changes that a sperm undergoes in the female reproductive tract and achieves the capacity to penetrate and fertilise the egg is called capacitation.
2. Attraction of sperm towards the egg.
3. Binding of sperm with zona pellucida.
4. Acrosome reaction: the acrosomal reaction allows the sperm to release acrosomal enzymes to penetrate the envelopes surrounding the egg.
Binding of sperm with zona pellucida of ovum is a highly specific reaction and receptors found on the zona pellucida facilitates interaction with the sperm. Due to the acrosomal reaction, the plasma membrane of both sperm and ovum fuses and as a result sperm can enter in the ovum.
After the sperm fuses with the egg, further entry of sperms is prevented by cortical reaction. Polyspermy is the entry of more than one sperm into the egg. This causes problems during development. It is prevented by cortical reaction.
5. Cortical reaction: the cortical reaction is a calcium-dependent reaction through which cortical granules present in the cytoplasm of egg are released via exocytosis process into the perivitelline space immediately after fertilization. The granules harden the zona pellucida and the sperm receptors on zona pellucida are lost. This prevents further entry of sperms.
Implantation is the intimate attachment of blastocyst (embryo) to the uterine wall and occurs after fertilisation.
The fusion of sperm with egg in human beings is preceded by the following steps.
1. Capacitation: changes that a sperm undergoes in the female reproductive tract and achieves the capacity to penetrate and fertilise the egg is called capacitation.
2. Attraction of sperm towards the egg.
3. Binding of sperm with zona pellucida.
4. Acrosome reaction: the acrosomal reaction allows the sperm to release acrosomal enzymes to penetrate the envelopes surrounding the egg.
Binding of sperm with zona pellucida of ovum is a highly specific reaction and receptors found on the zona pellucida facilitates interaction with the sperm. Due to the acrosomal reaction, the plasma membrane of both sperm and ovum fuses and as a result sperm can enter in the ovum.
After the sperm fuses with the egg, further entry of sperms is prevented by cortical reaction. Polyspermy is the entry of more than one sperm into the egg. This causes problems during development. It is prevented by cortical reaction.
5. Cortical reaction: the cortical reaction is a calcium-dependent reaction through which cortical granules present in the cytoplasm of egg are released via exocytosis process into the perivitelline space immediately after fertilization. The granules harden the zona pellucida and the sperm receptors on zona pellucida are lost. This prevents further entry of sperms.
Implantation is the intimate attachment of blastocyst (embryo) to the uterine wall and occurs after fertilisation.
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