8.1 The Placenta

Question 1

Describe the process of implantation

Answer 1

Uterine epithelium breached and conceptus implants within the stroma.

Question 2

What is meant by haemomonochorial?

Answer 2

One layer of cells separating the maternal and fetal blood supply

Question 3

Why is implantation important?

Answer 3

Establishes an area of exchange
Anchor the placenta
Establish maternal blood flow in the placenta

Question 4

What is a primary villi?

Answer 4

Early projections of trophoblast

Question 5

What is a secondary villi?

Answer 5

Invasion of mesenchyme into the core of the villi

Question 6

What is a tertiary villi?

Answer 6

Invasion of mesenchyme core by fetal vessels

Question 7

What is an ectopic pregnancy?

Answer 7

Implantation away from the uterine body eg. in the fallopian tubes

Question 8

What is placenta praevia?

Answer 8

Implantation in the lower uterine segment meaning the growth of the placenta covers the cervical opening. Requires a C-section and can cause haemorrhage

Question 9

What cells are involved in preparing the uterus for implantation?

Answer 9

Pre-decidual cells

Question 10

What is decidualisation?

Answer 10

Pre-decidual cells balance the invading force of the trophoblast so the fetus does not invade through the full-thickness of the endometrium

Question 11

What is special about the arterial supply in the endometrium?

Answer 11

Remodelled to create a low resistance vascular bed

This maintains the high flow required to meet fetal demand especially in late gestation

Question 12

What is pre-eclampsia?

Answer 12

Endometrial lining not replaced by fetal tissue so there is inadequate modification of the vessel walls

Question 13

What are the 3 ways of twinning occuring?

Answer 13

2 amniotic sacs, 2 chorionic sacs, 2 placentas

2 amniotic sacs, 1 chorionic sac, 1 placenta

1 amniotic sac, 1 chorionic sac, 1 placenta

Question 14

Describe the appearance of the 1st trimester placenta

Answer 14

Relatively thick

Complete cytotrophic layer under syncytiotrophoblast

Question 15

Describe the appearance of the full term trimester placenta

Answer 15

Thin barrier
Increased surface area
No cytotrophoblast layer

Question 16

What type of blood do the umbilical veins carry?

Answer 16

Oxygenated blood

Question 17

What type of blood do the umbilical arteries carry?

Answer 17

De-oxygenated blood

Question 18

What products does the placenta synthesise?

Answer 18

Glycogen, cholesterol, fatty acids
Progesterone, oestrogen
hCG, hCS, hCT, hCC

Question 19

What is the function of hCG?

Answer 19

Maintains the secretory function of the corpus luteum

Question 20

What is a molar pregnancy?

Answer 20

No fetal tissue
Only outer cell mass
Lots of hCG produced

Question 21

What is choriocarcinoma?

Answer 21

Tumour of the chorionic membrane

Question 22

Why does the placenta release progesterone?

Answer 22

Increase appetite to build up fat stores

Question 23

What substances move by diffusion across the placenta?

Answer 23

Water, electrolytes, gases, urea

Question 24

What substances move by facilitated diffusion across the placenta?

Answer 24

Glucose

Question 25

What substances move by active transport across the placenta?

Answer 25

Amino acids
Iron
Vitamins

Question 26

What substances move by receptor-mediated transport across the placenta?

Answer 26

IgG

Question 27

What is a teratogen?

Answer 27

Substance that can move across the placenta but is toxic to the fetus eg. alcohol, thalidomide

Question 28

What is haemolytic disease?

Answer 28

Rhesus blood group incompatibility of mother and fetus

Mother creates antibodies to the fetus and then gives them to the fetus

Question 29

Give 2 infections which can be passed on to the fetus

Answer 29

Varicella voster virus

Rubella