Placental Physiology and Early Embryology ✅

Question 1

What are the major functions of the placenta?

Answer 1

• Transport
• Immunity
• Metabolism

Question 2

What happens on day 1 of embryological development?

Answer 2

Fertilisation

Question 3

What happens on day 2 of embryological development?

Answer 3

Cleavage

Question 4

What is formed from cleavage in embryological formation?

Answer 4

The blastomere

Question 5

What happens on day 3 of embyrological development?

Answer 5

Compaction

Question 6

What is formed between cells during the compaction stage of embryological development?

Answer 6

A tight cell junction

Question 7

What happens on day 4 of embryological formation?

Answer 7

Differentiation

Question 8

What is formed from differentiation in embryological development?

Answer 8

An inner cell mass and a outer cell mass

Question 9

What happens on day 5 of embryological development?

Answer 9

Cavitation

Question 10

What happens to the embryo in cavitation?

Answer 10

The outer cell mass forms a trophoblast, and the blastocyst cavity develops

Question 11

What happens on day 6 of embryological development?

Answer 11

Zona hatching

Question 12

What happens on day 7 of embryological development?

Answer 12

Implantation

Question 13

What happens on day 9 of embryological development?

Answer 13

Cell mass differentiation

Question 14

What cell masses are formed from differentiation on day 9 of embryological development?

Answer 14

• Epiblast
• Hypoblast

(and have still trophoblast from before)

Question 15

What happens on day 12 of embryological development?

Answer 15

Bilaminar disc formation

Question 16

What happens on day 12 of embryological development?

Answer 16

Mesoderm formation

Question 17

Where does mesoderm form?

Answer 17

Between the ectoderm and the endoderm

Question 18

What happens on day 18 of embryological development?

Answer 18

Mesoderm spreading

Question 19

What happens on day 23 of embryological development?

Answer 19

Amniotic sac enlargement

Question 20

At what stage of early embryological development does the placenta start to develop?

Answer 20

As soon as the blastocyst implants in the uterine endometrium, forming the trophoblast

Question 21

How is the blood supply established in development of the placenta?

Answer 21

A network of umbilical vessels develop and branch through the chorionic plate to form villi

Question 22

At what stage of gestation is the blood supply complete on the maternal side of the placenta?

Answer 22

11-12 weeks

Question 23

What happens once the blood supply is complete on the maternal side of the placenta?

Answer 23

The uterine spiral arteries dilate and straighten and bathe the intervillous space with blood

Question 24

What are the transport functions of the placenta?

Answer 24

• Nutrients from mother to foetus
• Waste products from foetus to mother
• Gaseous exchange

Question 25

What methods of transport are utilised by the placenta?

Answer 25

- Simple diffusion for small molecules | - Active transport for larger molecules

Question 26

What gases is the placenta responsible for exchange of?

Answer 26

O2 and CO2

Question 27

What is the pO2 in the mother?

Answer 27

10-14KPa

Question 28

What is the pO2 in the foetus?

Answer 28

2-4KPa

Question 29

What happens once oxygen has diffused from the mother to the foetus?

Answer 29

It binds to fetal haemoglobin

Question 30

What facilitates the off-loading of oxygen from maternal Hb?

Answer 30

- Higher affinity of foetal Hb | - Change in maternal blood pH

Question 31

How does the affinity of foetal haemoglobin for oxygen compare to that of the mothers?

Answer 31

It has a higher affinity for a given pO2

Question 32

What is the immune function of the placenta?

Answer 32

- Prevention of rejection of the foetus | - Provides newborn with innate immunity to infectious diseases

Question 33

Why does rejection of the foetus not occur?

Answer 33

Because the trophoblastic cells appear non-antigenic, and so the maternal immune system does not react to it

Question 34

What may happen if some foetal cells do cross into the maternal circulation?

Answer 34

They can trigger an immune reaction

Question 35

Give an example of where disease can be caused by the immune reaction generated when foetal cells cross over into maternal circulation

Answer 35

Rhesus haemolytic disease

Question 36

Which maternal immunoglobulins are able to cross the placental barrier?

Answer 36

IgG

Question 37

Why is maternal IgG able to cross the placental barrier?

Answer 37

It is small

Question 38

Can IgM immunoglobulins cross the placental barrier?

Answer 38

No

Question 39

What are the metabolic functions of the placenta?

Answer 39

- Production of hormones | - Detoxification of drugs and metabolites

Question 40

What hormones are produced by the placenta?

Answer 40

- Human chorionic gonadotrophin (HCG) | - Human chorionic thyrotrophin (HCT)

Question 41

What is the result of the metabolic activity of the placenta meaning it has high energy demands?

Answer 41

It consumes over 50% of the total oxygen and glucose transported across it

Question 42

Is the placenta solely responsible for foetal homeostasis?

Answer 42

No

Question 43

What else is responsible for foetal homeostasis?

Answer 43

- Foetal liver - Foetal endocrine glands - Foetal kidneys

Question 44

What is the role of the foetal liver in homeostasis?

Answer 44

It produces albumin, red cells, and clotting factors

Question 45

What is the role of the foetal endocrine glands in homeostasis?

Answer 45

They produce thyroid hormone, insulin, and corticosteroids

Question 46

From what gestation do the foetal endocrine glands start to produce hormones?

Answer 46

12 weeks

Question 47

What is the role of the foetal kidneys in homeostasis?

Answer 47

They excrete large volumes of dilute urine

Question 48

At what gestation to the foetal kidneys begin to excrete dilute urine?

Answer 48

10-11 weeks

Question 49

What is the importance of the foetal urine?

Answer 49

It contributes to amniotic fluid volume