2.1 embrology - sepration & foetal shunts

Question 1

what is atrioventricular canal?

Answer 1

the hole in which the left & right atrium & ventricles develop from

Question 2

what are the different septations?

Answer 2

1. interatrial septum
2. interventricular septum
3. septation of ventricular outflow tract: pulmonary trunk & aorta

Question 3

how do you create septation?

Answer 3

develop endocardial cushions: atrioventricular region

divide heart into left & right channels (atrium and ventricles)

Question 4

what does atrium comminicate with ventricle via?

Answer 4

atrioventricular canal

Question 5

atrial septation - septum primum

Answer 5

1. septum primum grows towards fused endocardial cushions
2. ostium primum is a hole that forms before septum primum fuses with the endocardial cushion
3. before ostium primum closes, 2nd hole: ostium secundum appears in septum primum

Question 6

atrial septation - septum secundum

Answer 6

second crescent: septum secundum grows towards the endocardial cushion
the hole in septum secundum is foramen ovale

Question 7

right atrium derivative of primitive atrium

Answer 7

RA absorbs sinus venosus

Question 8

left atrium derivative of primitive atrium

Answer 8

LA sprouts from pulmonary vein

LA then grows to absorb the PV and its first 4 branches

Question 9

what is the remnant of the shunt used to bypass the lungs?

Answer 9

foramen ovale –> fossa ovalis

Question 10

name the components of ventricular septum

Answer 10

muscular

membranous

Question 11

how does the ventricular septum join with established structures?

Answer 11

the muscular portion forms most of the ventricular septum and grows UPwards towards the fused endocardial cushions
leaving a gap (primary interventricular foramen) to be filled in by membranous septum)

Question 12

septation of the outflow tract

Answer 12

the conotruncal septum
endocardial cushions also appear in the truncus arteriosus
as the endocardial cushions grow towards each other, they twist (spiral) so L–>R, R–>L (spiral septum) to create dual bloodflow

Question 13

When foetus is intrauterine, where does it receive oxygenated blood from?

Answer 13

mum via umbilical vein + plaenta

leaves via umbilical arteries

Question 14

which organs requires shunting from?

Answer 14

lung, liver, RV (goes to lungs)

Question 15

what happens after birth?

Answer 15

respiration begins, the LA pressure > RA, forces the 2 septums to shut close fusing together leaving small indentation in RA called fossa ovalis (foramen ovale closed)

Question 16

which shunt is used to bypass liver?

Answer 16

the ductus venaetus from placenta to inferior vena cava

closes after birth, becomes ligamentum venosum

Question 17

what is the foramen ovale and what is it used for?

Answer 17

bypass RV + lungs, from the ostium secundum of septum primum and opening of septum secudum
shut after birth, remains = fossa ovalis

Question 18

What happens to the ductus arteriosus

Answer 18

shunt to bypass the lungs: pulmonary trunk –> aorta

contracts to become firbotic vessel after birth (closed), called ligament arteriosum

Question 19

Name the 4 shunts and their fates after birth

Answer 19

foramen ovale –> fossa ovalis
ductus venaesus –> ligamentum venosum
ductus arteriosus –> ligamentum arteriosum
umbilical vein –> ligamentum teres (hepatis)