Fertilisation and Implantation Flashcards
What happens to the cell cycle following the LH surge
Prior to this, the oocyte is at prophase 1. Meiosis 1 completes and halts at______ _. So following ovulation there is an oocyte (______) with a ____ ____(first) and the zona pellucida.
Meiosis continues on fertilisation
Prior to this, the oocyte is at prophase 1. Meiosis 1 completes and halts at metaphase two. So following ovulation there is an oocyte (secondary) with a polar body (first), with the zona pellucida.
Meiosis continues on fertilisation
What happens with seminal and prostatic fluid in the female reproductive tract
Forms a _____ that adheres the ejaculate to the female tract.
______ of the fluid breaks this down and disperses the sperm. Occurs within __-__ minutes
Form a coagulum that adheres the ejaculate to the female tract.
Liquefaction of the fluid breaks this down and disperses the sperm
Why is it a difficult environment for sperm in the female tract?
note survival time post coitus 48 hours to 5/7 days
Also of 200,000,000 1,000,000 enter uterus
Vaginal pH acidic (4.5 average). Seminal fluid buffers to 7 ish
Cervical mucus: around periovulation, lots of and thin. Poor sperm can not go through due to lack of vibration
What is the transport time of sperm to ampulla of the fallopian tubes.
Why despite this pace may it take longer?
2-7 hours, when sperm go at about 20cm/hour
Speed is related to fertility, and speed decreases over time. Also decreases with freezing and thawing
What will the sperm do in the fallopian tubes?
typical site of fertilisation
Prior to ovulation will wait in the isthmus, beating of tails slows.
At ovulation sperm will move up to the egg and sperm may also be released from the crypts
Isthmus/ampulla junction
How do excess sperm in the uterus die off?
An innate immune response occurs, leucocytosis occurs and sperm are phagocytosed
What is sperm capacitation and what does it allow the sperm to do?
The removal of ____ ____ ____ such as _____ in the female tract (cervix?) because freshly ejaculated sperm can not _____.
_____ occurs. May facilitate sperm movement through the torturous folds of the fallopian tube due to increased _____ ____ and ____ ____ (hyperactivity). Also allows the _____ reaction to occur
The removal of capacitation inhibitory substances such as cholesterol in the female tract (cervix?) because freshly ejaculated sperm can not fertilise.
Hyperactivation occurs. May facilitate sperm movement through the torturous folds of the fallopian tube due to increased tail bending and head swinging (hyperactivity). Also allows the acrosome reaction to occur
What is the acrosome reaction and what is its role in fertilisation?
10% of sperm spontaneously do this too early.
ls inner acrosomal membrane contains ZP receptors
The emptying of the acrosome contents such as hyaluronidase due to progesterone or the ZP-3 protein of the zona pellucida causing calcium influx. (acrosomal and plasma membranes fuse)
Allows for fetilisation if the sperm is in close proximity to the oocyte.
How do the sperm cells get though the cumulus cells ans the corona radiata?
Due to a partial acrosome reaction (progesterone?) with the help of hyaluronidase to squeeze past the cumulus cells and then digests its way through the corona radiata
How does the sperm go through the zona pellucida and where do they go to
The presence of ZP-3 evokes the full acrosome reaction (acrosin). Pushes through the ZP to the perivitelline space before binding to the egg
What is the name of the oocyte membrane and how does sperm fuse?
Oolemma, when sperm fuses with this sperm nucleus enters. Facilitated by microvilli
What is the cortical reaction
When the sperm enters the egg, there is an increase in intracellular ____
Subsequent calcium spikes induce ____ and cause the release of _____ granules into the ______ space.
These granules release enzymes (proteases) that break down ____and cause ____ cross linking to prevent _____
When the sperm enters the egg, there is an increase in intracellular calcium.
Subsequent calcium spikes induce meiosis and cause the release of cortical granules into the perivitelline space.
These granules release enzymes (proteases) that break down ZP-2 and cause ZP-3 cross linking to prevent polyspermy
What occurs when meiosis resumes after fertilisation?
Meiosis continues from the metaphase 2 due to calcium rise.
Formation of another polar body, all kept within the ZP.
Formation of oocyte pronuclei which will fuse with the sperms
How long does it take the now zygote to reach the uterus? What happens in those 5 days
About 5 days, during whch the blastomeres are dividing symetrically.
Give rise to morula at 8-16 cell stage, tightly packed cells (3 days)
At about 4 days, is a blastocyst (60 cells). Differentiation has ocurred, and ZP starts to degrade.
What are the parts of the blastocyst and how long before it attaches to the uterine wall?
note whole process about 7 days
Trophectoderm that will form the trophoblast that forms the placenta and the inner cell mas that forms the embryo proper.
Won’t attach for 2-3 days to decidualendometrial epi
