Phys Of Pregnancy, Partuition, And Lactation

Question 1

What are the 3 barriers that sperm must breach to fertilize the egg?

Answer 1

Expanded cumulus
Zona pellucida
Plasma membrane of egg

Question 2

How does sperm bind to zona pellucida?

Answer 2

by binding to ZP3

Question 3

Describe the acrosomal reaction

Answer 3

Increase in Ca2+ inside sperm triggers fusion of outer acrosomal membrane with sperm cell’s plasma membrane and results in exocytosis of most of acrosomal contents
The spermatozoon can then penetrate zona pellucida

Question 4

Summarize process of fertilization

Answer 4

Sperm binds to ZP3 of egg
Acrosomal reaction
Enzymes dissolve zona pellucida
Sperm and egg membrane fuse
Cortical reacion to prevent polyspermy
Oocyte completes meiosis II
Sperm nucleus becomes pronucleus
Sperm and egg pronuclei fuse to form zygote

Question 5

Describe cortical reaction

Answer 5

Initiated by increase in Ca2+ in oocyte
Massive exocytosis of cortical granules
Enzymes act on glycoproteins in zona pellucida to make them harden
Prevents polyspermy

Question 6

Describe the completion of meisos II by oocyte

Answer 6

Results in 2nd polar body (haploid number of unduplicated maternal chromosomes)
Nucleus becomes pronucleus

Question 7

How does estrogen help regulate sperm transport?

Answer 7

Causes cervix to produce watery mucus that forms channels to aid passage of sperm through cervix
Only motile sperm can pass
Also cause contractions of myometrium to help propel sperm upward toward oviduct