Lecture 29 - Fertilization, Implantation, Assisted Reproductive Technologies

Lecture 29 - Fertilization, Implantation, Assisted Reproductive Technologies

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Lecture 29 - Fertilization, Implantation, Assisted Reproductive Technologies Relationship between capacitation, acrosome reaction and fertilization - Capacitation sperm enters the vagina o Changes that enable the spermatozoa to undergo acrosome reaction and hyperactivation o Normally this occur when semen interacts with vaginal fluids o Human cervical mucus plays a role in regulating sperm entry into the uterus Periovulatory mucus is water facilitating sperm movement through the open External os Luteal mucus is thick and resistant to sperm motion, and the external os is closed o Results of capacitation: sperm acquire the capacity to bind to zona pellucid Unmasking the ZP-3 receptor in the sperm membrane - Acrosome Reaction o Sperm attaches to the zona pellucid and plasma membrane is degraded & proteases are released o The sperm tail starts hyperactivity to reach the egg o Zona penetration The zona pellucida is locally hydrolyzed This together with hyper activation, allows the spermatozoon to penetrate the zona pellucid - The steps in fertilization o The binding of the sperm to the zona pellucida (outside of the egg) and the proteases are released and tail is hyperactive so sperm can reach the egg o Then a cortical reaction takes place and this prevents polyspermia (more than one sperm attaching to the egg) o If male is taking ca blockers, then this process may be hampered. o Ca dependent reaction! o Cortical reaction: blocks other sperms from binding to fertilized egg Sperm/oocyte contact triggers the cortical granule rxn that sweeps around the eggs Release of cortical granules around the periphery of the egg and this changes formation of zona pellucid preventing sperm from penetrating it After release, the contents of the cortical granules polymerize into a proteinaceous matrix that alters the structure of the zona pellucida ***The key events that occur during fertilization 1. Capacitated sperm binds to zona pellucida
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Lecture 29 - Fertilization, Implantation, Assisted Reproductive Technologies

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