Implantation

Question 1

Where does implantation occur?

Answer 1

Within the uterine stroma - in the decidual cells

Question 2

What are the 3 stages of implantation?

Answer 2

Apposition of blastocyst to endometrium epithelium
Adhesion to endothelium
Invasion of embryo into uterine decidua

Question 3

What are the aims of implantation?

Answer 3

To establish the basic unit of exchange (villi)
To anchor the placenta
Establish maternal flow within the placenta

Question 4

Explain the decidual reaction

Answer 4

provides the balancing force for the invasion of the trophoblast
stimulated by progesterone
access to spiral arteries
ensures not too much invasion and not too little

Question 5

What are the properties of the spiral arteries?

Answer 5

High flow, low resistance

Question 6

Name some implantation defects

Answer 6

Ectopic pregnancy
Placenta previa
Incomplete invasion and placental insufficiency (Eg. pre eclampsia)

Question 7

Explain how MZ twins can share the womb

Answer 7

Seperate placenta
Share chorion, 2 amniotic sacs
Share amnion

Question 8

What are twins that share the amnion at risk of?

Answer 8

Twin to twin transfusion syndrome
This is where one twin has too much of placenta and therefore is macrosomic, increased blood volume and heart failure and the other has restricted growth