12.3 Fertilisation and Implantation Flashcards
What are the two outcomes of capacitation?
- Sperm’s flagellum beats even more vigorously when it meets the oocyte (hyperactivity)
- Plasma membrane around acrosome to thin, permitting release of acrosomal enzymes during acrosome reaction.
Why are there millions of sperm in an ejaculate?
Because most of them will die due to the hazardous environment of the female reproductive tract
What obstacles that a sperm faces on its journey to the occyte?
- Acidity of environment (organic acids from glycogen breakdown overcome aklaline secretions from SV)
- Immune response from vagina or cervix (neutrophils and macrophages)
- Wrong oviduct
- Fail to penetrate cervical mucuous
How long does it take sperm to enter the cervix following deposition?
Approx 1 min
What happens to sperm that are deposited in the cervix
- Stored in cervical crypts
- Nourished by cervical mucus
For how long is a sperm viable?
48hrs
What is the lifespan of an oocyte?
~14hrs
How does the female physiology assist sperm movement?
- Uterine contractions
- Chemical attractants (?)
How long does it take sperm to release isthmus of uterine tube?
2-7 hours
How much time does sperm capacitation take?
10 hours
What is the name of the protein coat between the oocyte and the granulosa cells?
Zona pellucida
Do acrosomal enzymes destory granulosa cells?
- No
- They break the connections between them, enabling sperm to move through
When are the vast majority of acrosomal enzymes released from a sperm?
When the sperm reaches the zona pellucida
How is polyspermy prevented?
- Depolarization (Na+ influx into oocyte), electrostatically repelled from egg
- Cortical granule reaction (upon fertilization, cortical granules bind to plasma membrane. Material escapes from granules and binds to zona pellucida, hardening it)
