Implantation/Blastocyst Formation Flashcards
How does an extruded oocyte make its way into the fallopian tube?
It’s swept into the fallopian tube via the fimbriae
Where does fertilization normally take place?
In the ampullary region (the widest part) of the fallopian tube. Fertilization is usually
12 to 24 hours after ovulation
When does a secondary oocyte complete its second meiotic division to become a
mature ovum?
at fertilization
What are the three steps to actual fertilization?
Capacitation of sperm (final maturation step of sperm that takes place in female
reproductive tract—mediated by secretions from wall of uterus), acrosome reaction
(release of acrosomal enzymes allow sperm to penetrate the zona pellucida), and finally
fusion of sperm and oocyte membranes.
What three barriers must the sperm penetrate in order to fertilize the egg?
Corona radiata, zona pellucida, oocyte cell membrane
Sperm penetration of zona pellucida causes what to occur?
A: It causes cortical granules to release their contents which renders the zona pellucida
impenetrable to further sperm
What is pelvic inflammatory disease and how does it affect the fallopian tubes
It’s an STD (usually gonorrhea or chlamydia) that results in a purulent infection in the
fallopian tubes. This can cause narrowing or occlusion of the fallopian tubes which can prevent successful migration of the fertilized egg.
When is the 2-cell stage reached after fertilization?
approximately 30 hours
What another name for the ball of 16 cells that’s present 3 days after fertilization?
Morula
Describe blastocyst formation
As the morula enters the uterine cavity, fluid enters the zona pellucida and into the
intercellular spaces. Confluence of these intracellular spaces creates a cavity called the
blastocele.
What is blastocyst “hatching”?
The blastocyst is surrounded by the zona pellucida and it must “hatch” from it in order
to be able to implant into the endometrium.
What are the relevant structures of the blastocyst?
Inner cells, also called embryoblast. Outer cells, also called trophoblast, form the wall
of the blastocyst.
What’s special about the inner cell mass of the blastocyst?
Embryonic stem cells are derived from the inner cell mass. They’re pluripotent
What are some abnormal embedding sites for the blastocyst?
These are called ectopic pregnancies. Could be in the fallopian tubes (tubal) or near
the cervix (placenta previa) or, even more rarely, in the ovary or in the abdomen (pouch
of Douglas). Women with pelvic inflammatory disease have a high instance of ectopic
pregnancies. These are dangerous for the mother due to the possibility of internal
hemorrhage.
