Lecture 7 - 2018 Flashcards
What happens to meiosis following the LG surge?
Meiosis is resumed and the first division is completed. The process stops again, however, at second metaphase.
When will meiosis resume again at the second metaphase?
At fertilisation.
Describe meiosis after the LH surge?
There is an oocyte (2n) that will undergo meiotic division and will create an oocyte (n - 23 chromosomes) and the 1st polar body. The polar body is retained within the zona pellucida.
What happens to the sperm as it goes through the vas deferens?
As the sperm leaves the vas deferens and the urethra it is based in seminal plasma.
What happens to the seminal fluids and the prostatic fluids when they reach the vagina?
They come together in the vagina and form a coagulum - this is to hold the sperm together in the female reproductive tract.
What happens to the coagulum after 2-15minutes of ejaculation?
The coagulum is dispersed allowing for individual sperm to begin their quest for an egg.
What is the breakdown of the coagulum called?
Liquefaction - proteases break down the coagulum.
What happens is the sperm stays stuck in the coagulum?
They are not able to reach the fallopian tubes.
How does the sperm combat the acidic pH of the vagina (median 4.7)?
The seminal plasma forms a buffer, which drops the vaginal pH to 7.3 allowing the sperm to be motile.
What happens when the sperm reach the cervix?
Sperm move through the cervix at a rate of 1.2-3mm/min. Sperm have to get through the cervical mucous. The tails of normal sperm cause the fibres of the cervical mucus to vibrate in rhythm - if sperm is not normal it will not be able to induce this vibration in the mucous.
What happens to the cervical mucous around the LH surge?
It allows for a window of opportunity for sperm - the mucous has thinned out and allows for sperm to move through it.
What is the survival time for sperm?
Vagina - 2.5 hours.
Cervix - 48 hours.
Uterus - 24 hours.
Oviduct - 48 hours.
Clinical advice - sperm can last in the female reproductive tract for up to 5 days.
What is the transport time of sperm?
Sperm takes roughly 2-7 hours to reach the ampulla of the oviduct.
What is the swimming speed of sperm?
20cm/hr. Speed is related to fertility - speed decreases with time, freezing and thawing.
How much sperm can be found in a human ejaculate?
Up to 200,000,000 sperm, and of that only 1,000,000 will enter the uterus.
What do sperm do if they enter the fallopian tube prior to ovulation?
They slow down the beating of their tails and wait in the narrow isthmus of the tube.