Foetal Physiology

Question 1

Where does maternal fatal exchange occur ?

Answer 1

Placenta, at chorionic villi

Question 2

Where does maternal blood go in the placenta ?

Answer 2

Intervillous spaces

Question 3

Where does deoxygenated feral blood come from ?

Answer 3

Umbilical arteries

Question 4

How is pO2 in the foetus compared to the one in the maternal blood ?

Answer 4

Foetal pO2 much lower to make gradient so O2 can diffuse from maternal blood to foetal blood

Question 5

If foetal pO2 is low how does the foetus get all the oxygen necessary ?

Answer 5

Thanks to high haematocrit and foetal haemoglobin with higher O2 affinity than adult

Question 6

What factors apart from increased haematocrit of the foetus promote O2 exchange to the foetus ?

Answer 6

• physiological respiratory alkalosis increases maternal production of 2,3 DPG
• double Bohr effect at placenta

Question 7

How is an increased in 2,3 DPG beneficial for O2 exchange to the foetus ?

Answer 7

Makes maternal Hb give out O2

Foetal Hb isn’t affected by it , bind oxygen more easily

Question 8

Explain the double Bohr effect in the placenta

Answer 8

On mother side : as CO2 goes in intervillous blood, pH drops, shift curve to right , maternal blood affinity to oxygen decreases

On foetal side : as foetus Hb gives up CO2 , ph rises, increases foetal Hb affinity for O2

Question 9

What drives the transfer of CO2 from foetus to mother ?

Answer 9

Progesterone driven hyperventilation cause lower pCO2 in maternal blood so creation of gradient with foetal blood

Question 10

Describe the double Haldane effect

Answer 10

As Hb gives up O2 it can bind more CO2 and foetus gives up CO2 as O2 is accepted

Question 11

Is all the blood diverted from the lungs and right ventricle ?

Answer 11

No , small amount needed for development of lungs and to prevent right ventricle atrophy

Question 12

What re the names of the shunts ?

Answer 12

Ductus venosus : bypass liver
Ductus arteriosus : bypass lungs
Foramen ovale : bypass right ventricle (and lungs )

Question 13

Why is the ductus venosus needed ?

Answer 13

Liver is one of the biggest foetal organs and is very metabolically active
>bypassed in order to maintain saturation around 65% of the blood coming from placenta and gong to the rest of body

Question 14

Why is the Foramen ovale needed ?

Answer 14

Lungs aren’t functional (no gas exchange ) , don’t need too much blood and can’t resist pressure

Also so that oxygenated blood can reach left ventricle and be used by brain and heart with high saturation

Question 15

How does the right ventricle receive a small amount of blood ?

Answer 15

Border of septum Secundum forms Crista dividens which create 2 streams of blood

One goes in LA the other in RV

Question 16

What happens at birth for the Foramen ovale ?

Answer 16

Pressure in right atrium becomes higher than in left pushing two septum together and closing the Foramen

Question 17

Why is the ductus arteriosus needed ?

Answer 17

Blood from RV to go in aorta not to lungs (can’t resist pressure )

Joins aorta distal to supply to head and heart so O2 stats for head and heart stays high

Question 18

How is hypoxia in foetus prevented ?

Answer 18

Foetal Hb and increased haematocrit

Question 19

What happens in the foetus if hypoxia occur ?

Answer 19

• redistribution of flow to heart and brain
• foetal chemoreceptors detect low O2 and high CO2 causing > vagaries stimulation > bradycardia&raquo_space; slows HR to decrease oxygen demand

Question 20

How is adaptation to hypoxia different in foetus and adult ?

Answer 20

Foetus : vagal stimulation > bradycardia

Adult : vagal inhibition > tachycardia

Question 21

What are the consequences of chronic hypoxaemia on the foetus ?

Answer 21

Growth restriction 
Behavioural impact (impact on development : decreased movement , sleep pattern ...)

Question 22

What causes chronic hypoxaemia in foetus ?

Answer 22

If mother smokes

Question 23

What is normal foetal HR ?

Answer 23

120-160 bpm

Question 24

Which hormones are critical for foetal development ?

Answer 24

Insulin like growth factor IGF

Not growth hormone

Question 25

What are the effects of nutrition on foetal growth ? What are the two types ?

Answer 25

Malnutrition can cause growth restriction
Symmetrical : proportionate , small everywhere
Asymmetrical : head sparring but abdomen is small

Question 26

Which cellular growth type is dominant before 20 wks , between 20 and 28 wks and after 28 wks ?

Answer 26

Hyperplasia

Hyperplasia+hypertrophy

Hypertrophy

Question 27

What is the function of the amniotic fluid ?

Answer 27

Protects foetus

Contributes to lungs development

Question 28

How much amniotic fluid is there at 8 wks and at term ?

Answer 28

10 mL at 8 wks

1 Litre at term

Question 29

How is the majority of the amniotic fluid produced ?

Answer 29

By foetus kidneys

Question 30

When does urine production start ?

Answer 30

Week 9-10

Question 31

How does amniotic fluid help in lung development ?

Answer 31

Practice breathing movement

Contains factor necessary for development (of type1 and 2 pneumocyte)

Question 32

Why can there be too much or too little amniotic fluid ?

Answer 32

Too much : no ingestion by foetal GI tract (obstruction, tracheo oesophageal septum defect, duodenal atresia …)

Too little: non functioning kidney , leakage …

Question 33

What is the composition of the amniotic fluid ?

Answer 33

98% water
Electrolytes,creatinine,urea,bile pigments, glucose, hormones ,cells
Lanugo (fine hair covering foetus )
Vernix caseosa (wax covering skin )

Question 34

What is the meconium ? How is it clinically relevant ?

Answer 34

Accumulation in GI tract Made of debris from the amniotic fluid and intestinal secretions (bile)

Passed as first bowel movement

If foetal distress : can be excreted in amniotic fluid

Question 35

How is bilirubin cleared during gestation Why ? What can happen at birth ?

Answer 35

Handled by placenta then mother

Felt us can’t conjugate bilirubin due to immaturity of liver and intestinal processes

Can see Physiological jaundice at birth