Lecture 21 Flashcards
What is capacitation
a maturation sperm must undergo in order to fertilize an egg
when does capacitation occur
once sperm is in the female tract
where do you find capacitation inhibiting factors
seminal fluid
What 2 things occur after capacitation
higher motility pattern (faster flagellum)
plasma membranes become more fragile
What does a more fragile sperm membrane do for the sperm
facilitates acrosome reaction
what is the acrosome reaction
fusion of acrosomal membrane and PM and releasing of enzymes
How can IVF induce capacitation
by washing sperm/ running them through a Percoll gradient
What induces the acrosome reaction
Binding of sperm to zona pellucida
What is polyspermy
when more than 1 sperm penetrate the oocyte
What is it called when more than 1 sperm penetrates the oocyte
Polyspermy
How does capacitation occur
Female secretions remove protein and some cholesterol that makes acrosomal membranes tough and stable
Name two mechanisms that prevent polyspermy
Oocyte membrane block
Cortical reaction
The cortical reaction helps f=prevent
polyspermy
the membrane block helps prevent
Polysperm
Describe the oocyte membrane block
Once a sperm binds, the oocyte sheds any other receptors so that no other sperm can bind
Waves of what are released when the sperm and oocyte membranes fuse
Calcium
What does the wave of calcium from the oocyte’s endoplasmic reticulum into the cytoplasm cause
The cortical reaction
What is the cortical reaction
exocytosis of granules located just inside the plasma membrane
What occurs in the cortical reaction
granules from the PM contain enzymse that destroy the zona pellucida’s sperm-binding receptors and harden the zona pellucida
What is the male pronucleus
when the sperm’s nucleus swells to about 5 times it’s original size
what is it called when the sperm’s nucleus swells to about 5 times it’s original size
male pronucleus
an efflux of what allows the oocyte to complete meiosis II
zinc
what makes the oocyte complete meiosis II
fertilization
what is it called when the ovum nucleus swells
female pronucleus
what is the female pronucleus
when the ovum nucleus swells
when does the female pronucleus appear
when meiosis II is complete
what occurs between the two pronuclei as they approach one another
they fuse, and form the 2N of the zygote
Describe cleavage
period of fairly rapid mitotic divisions of the zygote without intervening growth
what is the goal of cleavage
produce small cells with a high surface-to-volume ratio, which enhances their uptake of nutrients and oxygen and the disposal of wastes
the first cleavage division of the zygote produces two identical cells known as
blastomeres
what is a morula
a cluster of cells formed 72 hours after fertilization