FERTILISATION Flashcards
The ovulated oocyte is called—. why is it ovulated?
secondary oocyte
Meiosis 2 is resumed due to LH surge 24 hours prior to ovulation
the oocyte is only viable for —. — and — are also ovulated with the oocyte. They are important in — that —-. Also involved in Ca transients which —– —–.
24 hours
Ovulated corona radiata and follicular fluid
– Important in chemoattractants that attract
sperm
– Also involved in Ca2+ transients that initiate
acrosome reaction
—- sperms per ejaculate which are deposited in —-. This protects the sperm from —- and avoid — in vagina.
The sperm can survive up to— in female repro
Millions per ejaculate Deposited in anterior vagina – Not exposed to vaginal acidic environment – Avoid immune cells in vagina Can survive 5 days in female reproductive tract
why does sperm need to be capacitated in female repro?
because it was decapacitated in epididymis , need them for fertilisation
sperm capacitation occurs in —-, involves —- (as an —), and —- of —- and —-.
Female reproductive tract – Removal of cholesterol Inhibitor of capacitation – Redistribution of phospholipids and carbohydrates
sperm capacitation is important because it —- to —via —.
Necessary for fertilisation
Increase affinity to bind to ZP
proteins
– via Acrosome reaction
An indication of sperm capacitation is —- and —-.
Hyperactivation of sperm
Increase in tyrosine
phosphorylation
– Clinical marker for sperm capacitation
what occurs in the spermatozoa during maturation, ejaculation and capacitation of sperm?
During maturation in epididymis-accumulation of proteins that will help to bind to ZP, and decapacitation.
During ejaculation the decapacitation proteins are in seminal fluid.
In Upper female reproductive tract –
– Removal of decapacitation factors
– Redistribution of proteins to allow binding to ZP
proteins
What occurs as the result of sperm hyperactivation?
When sperm approach secondary oocyte Sudden influx of Ca2+ through CatSpers – Cationic channels of sperm – On tail Tail becomes more active and bends more forcefully – allowing Faster movement
List the steps in fertilisation?
- Capacitation
- Penetrate corona radiata
- Penetrate zona pellucida
- Fusion of sperm and oocyte membranes
PS. once the sperm in cyto of oocyte it is without its plasma membrane
How does sperm penetrate corona radiata?
Release of hyaluronidases from acrosome
Tubal factors
Movement of sperm tail (hyperactivated)
– Part of sperm hyperactivation
How does penetration of zona pellucida occur?
Acrosome enzymes
– Especially acrosin
– Lysis of zona pellucida in small area to allow
sperm entry
Initiates zona reaction to prevent polyspermy
– Only 1 sperm enters perivitelline space (between
zona pellucida and oocyte membrane)
Outline the steps required to prevent polyspermy?
- Fast block to polyspermy
– Long lasting depolarisation of oocyte membrane
– Transient electrical block to polyspermy
– Activation of Ca2+-activated Cl- channels - Cortical Reaction
– Change in polarity leads to Ca2+ release
– Cortical granules move to surface and fuse
with oocyte membrane
– Transient increase in membrane surface area
and reorganisation of membrane - Zona Reaction-final permanent step
– Protease in cortical granules
– Degrade glycoproteins that bind to sperm
– Form perivitelline membrane
Cross-lining of ZP proteins
– Final and permanent block
—- goes into oocyte, — and
—- left behind.
—- in sperm
reactivates oocyte cell cycle (previously
arrested at —)
Sperm binds to oolema via fertilin and fuses Sperm head into oocyte, mitochondria and plasma membrane left behind Phospholipase C-zeta in sperm reactivates oocyte cell cycle (previously arrested at metaphase II)
After activation of oocyte cell cycle in fertilisation, the male — is formed (now called an — because it has —).
They fuse to form a — (—).
Then —- to — stage occurs which is the —-.
Male pronucleus formed – now called an ootid (2 pronuclei) 2 pronuclei fuse to form a zygote (2n) Mitotic cleavage to 2-cell stage – Start of embryonic development
