Foetal Circulation

Question 1

how are oxygen and nutrients supplied to the foetus

Answer 1

• placenta

Question 2

the foetal heart and blood vessel are essential to carry ___ and ____ to foetal ____ & to remove ____

Answer 2

• oxygen and nutrients
• to foetal tissues
• remove waste

Question 3

how does nutrient supply from the placenta enter

Answer 3

• via umbilical veins

Question 4

what is present in the foetal circulation that allow different pattern of blood flow in foetus compared to adult

Answer 4

three shunts

Question 4

name of the three shunts

Answer 4

• ductus venosus
• ductus arteriosis
• foramen ovale

Question 4

location of the ductus venosus

Answer 4

in the liver circulation
between umbilical vein and inferior vena cava

Question 5

function of ductus venosus

Answer 5

• allows o2 and nutrient rich blood, coming form the placenta in the umbilical cord, to mostly bypass the foetal liver, diverting blood into inferior vena cava which leads to the foetal heart

Question 6

why is the ductus venosus able to mostly bypass the foetal liver blood supply

Answer 6

• immature foetal liver plays smaller role in metabolism than it does in adult
• only requires a small flow of blood to meet its needs

Question 7

replenished blood from the placenta flowing through the ductus venosus mixes with what

Answer 7

foetal venous blood returning through foetal veins to the heart

Question 8

the non-inflated foetal state means what for the foetal lungs

Answer 8

they are non-functional

Question 9

due to non-inflated state, resistance to blood flow in pulmonary circulation is ____

Answer 9

very high

Question 10

how are foetal lungs bypassed

Answer 10

• majority of highly oxygenated foetal blood from inferior vena cava is shunted directly from right atrium into left atrium thru foramen ovale

Question 11

what blood mixes in left atrium from expected and shunted blood

Answer 11

• deoxygenated blood from pulmonary vein that has travelled through developing lungs
• oxygenated blood from right atrium through foramen ovale

Question 12

describe the rest of the normal blood supply from heart after left atrium

Answer 12

blood in left atrium -> moves to left ventricle -> pumped into aorta -> supplies foetal tissues and organs

Question 13

how is foetal heart and foetal brain supplied with blood

Answer 13

same as others from being pumped into aorta
- goes to heart via coronary arteries
- goes to brain via carotid arteries

Question 14

why is the blood from the IVC going into the right atrium mostly oxygenated blood

Answer 14

• due to the ductus venosus
• oxygenated blood coming from placenta is being diverted to IVC and to heart

Question 15

why is blood coming from the pulmonary veins not oxygenated blood

Answer 15

because the lungs are non-functional so are not oxygenating them as they are developing

Question 16

where does the remaining blood in the right atrium of the heart go

Answer 16

pulmonary artery
which is standard for adult circulation

Question 17

does the blood that goes into pulmonary artery go to the foetal lungs

Answer 17

• some does
• able to bypass lungs by entering ductus arteriosus

Question 18

what does the ductus arteriosus connect

Answer 18

• pulmonary artery with the aorta

Question 19

what does resistance to blood flow in the pulmonary circulation is very high mean

Answer 19

it is difficult for blood to pass through the blood vessels in the lungs

Question 20

why is flow into the aorta favoured over the foetal lungs

Answer 20

• because the aorta has low resistance
• high resistance in foetal pulmonary vessels

Question 21

why

Answer 21

deoxygenated blood normally comes from IVC
so the normal blood in the RA is deoxygenated if its not from the ductus venosus
some of the RA blood will go via the ductus arteriosis to the aorta and still be deoxygenated
some of the RA blood will go to the lungs and still be deoxygenated and be in left atrium where ends up in aorta deoxygenated (normal route except lungs not functioning so not oxygenated)

Question 22

why is blood flowing through the descending aorta a mix of oxygenated blood and partly deoxygenated blood

Answer 22

• oxygenated blood from placenta that has been through ductus venosus and foramen ovale or ductus venosus and ductus arteriosus
• deoxygenated blood that has been passed thru foetal tissues (removed nutrients too)

Question 23

after blood has been circulated from the descending aorta to the foetal tissues, how does it return to the placenta

Answer 23

• branches of the internal iliac arteries flow into the two umbilical arteries to return this blood to placenta

Question 24

why is blood returned to the placenta

Answer 24

• replenished with oxygen and nutrients from maternal circulation