Foetal Physiology

Question 1

Describe the structure of foetal haemoglobin.

Answer 1

2 alpha + 2 gamma sub units, increased affinity for oxygen.

Question 2

Describe how RBC’s are produced in the foetus.

Answer 2

Initially RBC’s are made in the yolk sac but by 16 wks should have moved to the liver and eventually the bone marrow.
Yolk sac –> Liver –> Bone Marrow.

Question 3

Describe the pathology of thalassmia.

Answer 3

Congenital abnormality with Hb chain- alpha or beta sub unit.
RBC’s are broken down at too quick a rate and the liver can take over again and become enlarged.

Question 4

What is Hypoxic pulmonary vasoconstriciton?

Answer 4

Hypoxic pulmonary vasoconstriciton: in the lungs low oxygen means vasoconstriction, opposite of the rest of the body where hypoxia = vasodilation.

Question 5

Describe the basic structure of foetal circulation.

Answer 5

1 umbilical vien, 2 umbilical arteries
3 shunts: 
Ductus venosus= 50% bypasses the liver  
Foreman ovale= RA --> LA
Ductus arterosus= Pulmonary artery --> Aorta

Question 6

Describe the process of foetal circulation

Answer 6

1) blood in through umbilical vein
2) Umbilical vein travels to liver:
- 50% goes through to build up glycogen stores
- 50% DUCTUS VENOSUS bypass the liver
3) IVC -> RA
4) RA-> LA-> LV -> Aorta
5) Any blood that goes through RV can go from pulmonary artery -> DUCTUS ARTEROSIS -> aorta

Question 7

What keeps the ductus arterosus open?

Answer 7

DA is open by prostaglandins made by the placenta
COXi -> close duct so avoid aspirn etc
Prostaglandins -> keep open

Question 8

Why is taking aspirin in pregnancy risky?

Answer 8

COXi can cause the DA to close.

Question 9

What happens to the foetal circulation after birth?

Answer 9

Clam down on vessels:
Decreased temperature outside the mothers body causes the umbilical artery and vein to contract. Midwives add a clamp on too.
First breath:
Fluid is forced out of the lungs and air fills. Vasodilation of arterioles and decreased lung resistance. Less resistance in the lungs so RA

Question 10

What can happen if the foetal circulation fails to swap to adult?

Answer 10

Failure of pulmonary resistance to fall –> ductus arteriosus stays patent –> left to right shunt–> cyanosis
Risks:
NEC
Intravascular haemorrhage

Question 11

Describe the key developmental milestones of the lungs.

Answer 11

20wks: structures present
22-24wks: blood vessels become aligned with alveoli
24-28wks: type 2 pneumocytes begin to develop and make surfactant.

Question 12

Who will be affect by RDS? & what is the treatment?

Answer 12

Preterms <28wks

Antenatal corticosteroids + surfactant + ventilation

Question 13

What factors could cause lungs to not develop properly?

Answer 13

oligohydramnious: as lungs are filled with fluid

Diabetes mellitus- causes type 2 pneumocytes to develop later.

Question 14

What are the common infections in preterms?

Answer 14

Toxoplasmosis 
Other: coxsackie, chickenpox, chlamydia 
Rubella 
Cytomegalovirus
Herpes

Question 15

Why are preterms more vunerable to cold?

Answer 15

Thin skin + no vernix

Question 16

Describe normal mid gut development

Answer 16

1) loop of endoderm herniates out of abdomen as not enough space with all other structures e.g. liver
2) Rotates around superior mesenteric artery
3) by wk 12 back in abdomen

Question 17

What happens if there is failure of the midgut to properly develop?

Answer 17

Midgut fails to return into the abdomen you can get omphalocoele or gastroschisis

Question 18

How can you tell the difference between omphalocoele and gastroschsis?

Answer 18

Covered in amniotic sac -> omphalocoele

No amniotic sac –> gastroschsis

Question 19

What causes omphalocoele &gastroschsis?

Answer 19

omphalocoele –> associated with trisomys

gastroschsis –> deficient weak abdominal wall.

Question 20

Why might there be polyhydramnious?

Answer 20

Failure of the swallow reflex
The foetus swallows alot of amniotic fluid if there is a failure e.g. neurological/ gut obstruction then fliud can build up.

Question 21

What is the meconium?

Answer 21

The first poo

Question 22

What are the concerns with meconium stained fluid?

Answer 22

foetal distress and hypoxia

meconium aspiration syndrome

Question 23

Describe energy storage in the foetus.

Answer 23

Energy stores are only really laid down in the last trimester as fat increases x5

Question 24

What is the function of the liver in utero?

Answer 24

Liver produces RBC from 6-36wks
Stores glycogen
Does not yet conjugate billirubin

Question 25

Why are premature babies at increased risk of jaundice?

Answer 25

Liver does not start producing enzymes to conjugate bilirubin until late pregnancy and relies on the placenta.

Question 26

Describe the embryonic origins of the different parts of the kidney.

Answer 26

Mesonephros - secretory system e.g. pelvis, caylces, urters

Metanephros- nephrons

Question 27

What in utero issues could renal agenesis cause?

Answer 27

Renal agenesis could cause oligohydramnious as the foetal kidney produces most amniotic fluid

Question 28

When are foetal movements first felt?

Answer 28

18-20wks in primagravida

Question 29

What could decreased foetal movements indicate?

Answer 29

Hypoxia
IUGR
Foetal demise