6.1 Placental Function And Dysfunction

Question 1

When does the placental begin to develop?

Answer 1

Second week of development

Question 2

What does the outer cell mass differentiate into in week 2?

Answer 2

Syncytiotrophoblast

Cytotrophoblast

Question 3

What does the inner cell mass differentiate into in week 2?

Answer 3

The bilaminar disk

• Epiblast
• Hypoblast

Question 4

What two cavities are within the embryo by end of week 2?

Answer 4

Yolk sac

Amniotic cavity

Question 5

What is the embryo suspended in by end of week 2 and by what structure is it suspended?

Answer 5

Chorionic cavity

Suspended by a connecting stalk

Question 6

What happens to the yolk sac?

Answer 6

Disappears

Question 7

What happens to the amniotic sac and chorionic sac?

Answer 7

The amniotic sac enlarges

Chorionic cavity becomes occupied by the expanding amniotic cavity

Question 8

What are primary villi?

Answer 8

Early finger-like projections of trophoblast

Question 9

What are secondary villi?

Answer 9

Invasion of mesenchyme into core

Question 10

What are tertiary villi?

Answer 10

Invasion of mesenchyme core by foetal vessels

Question 11

Name three things that implantation achieves

Answer 11

Establishes a basic unit of exchange
Anchors the placenta
Establishes maternal blood flow in the placenta

Question 12

Where does the conceptus implant?

Answer 12

Within the stroma (uterine epithelium is breached)

Question 13

Implantation is interstitial, true or false?

Answer 13

True

Question 14

What ultimately separates the maternal blood from the foetal capillary wall?

Answer 14

One layer of trophoblast

Question 15

Why does the placental membrane become progressively thinner?

Answer 15

Needs of foetus increase

Question 16

What is the placental a specialisation of?

Answer 16

The chorionic membrane

Question 17

What are the two categories of implantation defect?

Answer 17

Implantation in wrong place

Incomplete invasion

Question 18

What can implantation in the wrong place cause?

Answer 18

Ectopic pregnancy

Placenta previa

Question 19

What can be caused by incomplete invasion?

Answer 19

Placental insufficiency

Pre-eclampsia

Question 20

Define ectopic pregnancy

Answer 20

Implantation at site other than uterine body
Often Fallopian tubes
Can be ovarian or peritoneal
Endometrial areas normally provide modulation of the invasive force - doesnt happen in ectopic pregnancy

Question 21

What is placenta previa?

Answer 21

Implantation in the lower uterine segment
Can cause haemorrhage
May need a C section

Question 22

What happens to the endometrium in the presence of the conceptus?

Answer 22

Transforms into the decidua

Question 23

What does the decidual reaction do?

Answer 23

Provides the balancing force for the invasive force of the trophoblast

Question 24

What can be seen on the foetal aspect of the placenta (gross morphology)?

Answer 24

Umbilical cord -> Umbilical vessels -> Chorionic vessels

Amnion

Question 25

What can be seen on the maternal aspect of the placenta?

Answer 25

Cotyledons

Question 26

Describe the chorionic villus in the first trimester

Answer 26

Thicker barrier Complete layer of cytotrophoblast Acts as a stem cell layer for syncytiotrophoblast

Question 27

Describe the third trimester chorionic villus

Answer 27

Barrier at optimal thickness | Occasional cytotrophoblast cell but they have mainly regressed

Question 28

How many umbilical arteries are their and what do they do?

Answer 28

2 | Deoxygenated blood from foetus to placenta

Question 29

How many umbilical veins are there and what is the role of them?

Answer 29

One | Oxygenated blood from placenta to foetus

Question 30

What two types of hormones does the placenta produce?

Answer 30

Protein | Steroid

Question 31

What are the protein hormones of the placenta?

Answer 31

Human chorionic gonadotrophin Human chorionic somatomammotrophin Human chorionic thyrotrophin Hyman chorionic corticotrophin

Question 32

Which steroid hormones are produced by the placenta?

Answer 32

Oestrogen | Progesterone

Question 33

When is hCG produced and what by?

Answer 33

During the first 2 months of pregnancy | By the syncytiotrophoblast

Question 34

What is the role of hCG?

Answer 34

Supports the secretory function of the corpus luteum

Question 35

Why can hCG easily be used as the basis for pregnancy testing?

Answer 35

Excreted in maternal urine

Question 36

What is the function of placental steroid hormones?

Answer 36

Maintain the pregnant state

Question 37

When does placental production of steroid hormones take over from the corpus luteum?

Answer 37

11th week

Question 38

How do placental hormones influence maternal metabolism?

Answer 38

Progesterone - Increased appetite hCS, hPL - Increase glucose availability to foetus - Maternal insulin resistance

Question 39

What are the two types of transport in the placenta?

Answer 39

Simple diffusion Facilitated diffusion - glucose Active transport

Question 40

Why do we need an adequate uteroplacental circulation?

Answer 40

To maintain the oxygen gradient to the foetus

Question 41

What active transporters are expressed and by what?

Answer 41

Syncytiotrophoblast | Amino acids, iron, vitamins

Question 42

Which molecule is transferred in passive immunity and by what process?

Answer 42

IgG | Receptor mediated

Question 43

What can Rhesus incompatibility of the mother and foetus cause?

Answer 43

Haemolytic disease

Question 44

Name some harmful substances that can cross the placenta

Answer 44

Thalidomide, alcohol, therapeutic drugs (anti-epileptics, warfarin, ACE inhibitors), drugs of abuse

Question 45

Why does thalidomide cause limb defects?

Answer 45

Crosses the placenta and destroys small blood vessels (in developing limbs)

Question 46

What are the consequences of maternal smoking on the placenta?

Answer 46

Smaller placenta | Calcification