Lecture 8: Implantation

Question 1

How long after fertilization does implantation begin?

Answer 1

Day 6

Question 2

Blastocyst hatching

Answer 2

A small region of the zona pellucida overlaying the ICM dissolves and the blastocyst emerges, “shedding” the ZP in preparation for implantation

Question 3

Functions of the zona pellucida

Answer 3

Promotes oocyte/follicle maturation, initiates acrosomal reaction, prevents polyspermy, acts as early immunological barrier between mother/embryo, facilitates trophoblast differentiation, prevents premature implantation

Question 4

List the 4 stages of Implantation

Answer 4

1. Attachment of blastocyst to endometrium
2. Penetration of uterine epithelium
3. Invasion into tissues underlying epithelium
4. Erosion of maternal vascular supply

Question 5

Which of the following is a function of the zona pellucida?

A. Nutritional supply for the egg
B. Initiates acrosomal reaction
C. Both of the above
D. Neither of the above

Answer 5

B. Initiates acrosomal reaction

Question 6

What type of molecules facilitate attachment of blastocyst to endometrial epithelium?

Answer 6

Adhesion molecules such as integrins

Question 7

What significant event occurs during the penetration of uterine epithelium?

Answer 7

Trophoblast separates into cytotrophoblast and synctiotrophoblast

Question 8

Trophoblastic lacunae

Answer 8

Hollow cavities within syncytiotrophoblast which fill with maternal blood as endometrial blood vessels erode

Question 9

Decidual reaction

Answer 9

Response of endometrial stroma cells to invading blastocyst; necessary because otherwise the trophoblast could potentially erode all the way through the endometrial wall

Question 10

What is the result of the decidual reaction?

Answer 10

A massive cellular matrix that completely surrounds the embryo and fills most of the endometrium, IL-2 secreted to protect embryo from rejection

Question 11

Ectopic pregnancy

Answer 11

Occurs when embryo is implanted somewhere other than the uterine wall