Pregnancy And Contraception Flashcards
What happens to ejaculated semen initially ?
It coagulates due to prostatic and seminal vesicle secretions, then liquefies in about 15 minutes
What does movement through the cervical mucus remove from sperm?
It removes seminal fluid, abnormally shaped sperm, and cellular debris
Why is cervical mucus less vicious, and what does this allow?
It’s less vicious under the influence of oestrogen and in the absence of progesterone, allowing sperm to pass through.
What function might cervical crypts serve for sperm ?
They can act as reservoirs where sperm may inhabit
How long after ejaculation does fertilisation typically occur?
Fertilisation typically occurs with 24-48 hours.
What is sperm capacitation?
Partly achieved by removing the sperm from the seminal fluid, also uterine or tubal fluid may contain factors which promote capacitation.
Biochemical rearrangement of the surface glycoprotein and changes in membrane composition must occur before the acrosome reaction can occur.
What triggers the acrosome reaction ?
The acrosome reaction is triggered when the sperm contacts the zona pellucida, the glycoprotein layers surrounding the oocyte
What happens to the acrosome membrane during the acrosome reaction?
The outer membrane of the acrosome fuses with the sperms plasma membrane, creating pores and releasing enzymes that digest the zona pellucida. Allowing sperm to penetrate the oocyte.
What role does acrosin play in the acrosome reaction ?
Acrosin , bound to the inner acrosomal membrane, further helps digest the zona pellucida to facilitate sperm entry.
Sperm binding and penetration: how does sperm approach the cumulus complex ?
The sperm swims more forcefully as it approaches, and hyaluronidase on its surface helps it penetrate the cumulus cells (cells which promote the growth of oocytes)
Sperm binding and penetration: What does binding to the zona pellucia (ZP) trigger?
Binding to the ZP triggers the acrosome reaction, releasing enzymes that cut through the ZP and allowing the sperm to fuze with the eggs plasma membrane
How is sperm taken into the egg?
The sperm is engulfed by the egg through phagocytosis. Phospholipase Zeta, activated by Ca2+, triggers a signalling cascade causing the release of intracellular Ca2+ .
