Unit 1 - Pregnancy & Placentation

Question 1

What do the Trophoblasts that invade the endometrium during implantation turn into?

Answer 1

become a network of syncytiotrophoblasts- forms the placenta

Question 2

What is the role of the placenta?

Answer 2

mobilisation of oxygen, provision of nutrients, removes waste products

Question 3

What does Haemochorial mean? What is this regarding?

Answer 3

extremely invasive with three layers of separation- Placenta (specifically primates)- can be classified based on their degree of cellular seperation between foetal & maternal blood.

Question 4

What does Epitheliochorial mean? What is this regarding?

Answer 4

non invasive, 6 layers of separation & minimal blood loss at Partuition
regarding sheep placentas

Question 5

Progesterone synthesis occurs via the ______ _______ until the _______ takes over

Answer 5

corpus luteum

placenta

Question 6

What is Passive Luteolysis?

Answer 6

Blastocyst trophoblast cells produce luteotropic factor, chorionic gonadotrophin binds to the LH receptor to maintain LH levels and stop the Corpus Luteum regressing

Question 7

What is Active Luteolytic action?

Answer 7

Luteolytic compound production is blocked to prevent Corpus Luteum breakdown

Question 8

Which animal/ group of animals does Passive Luteolysis occur in? What about Active?

Answer 8

Passive- haemochorial e.g. primates

Active- epitheliochorial e.g. Sheep

Question 9

Why does Human Chorionic Gonadotrophin fall after week 12 of pregnancy?

Answer 9

this is the point when the corpus luteum regresses and the placenta takes over progesterone production

Question 10

What is PGF2alpha? Where is it released?

Answer 10

induces Luteolysis-

released from the uterus via oxytocin receptors

Question 11

Progesterone is derived from what during pregnancy?

Where is it synthesised?

Answer 11

Derived from maternal cholesterol

Synthesised in placental Trophoblasts

Question 12

How are Androgens produced during Pregnancy?

Answer 12

1. foetal adrenal glands convert progestogens to C19 androgen dehydroepiandrosterone (DHA)
2. Foetal liver then converts progesterone to androstenedione

Question 13

androgens are a substrate for ______ _______

Answer 13

oestrogen production

Question 14

Oestradiol is formed from ….

Answer 14

DHA (maternal or foetal adrenal)

Question 15

Oestrone is formed by _____

Answer 15

DHA (from maternal or foetal)

Question 16

Oestriol is formed from …..

Answer 16

16alpha- hydroxylated androgens from the foetal liver

Question 17

How does the Placenta protect the foetus from high levels of steroids in the mother?

Answer 17

Placenta de-sulphates steroids, releasing free biologically active hormones into the mother.