L5 - Embryology 1

Question 1

In what week does embryonic folding occur?

Answer 1

4th week

Question 2

In what week does gastrulation occur?

Answer 2

3rd week

Question 3

Describe the formation of the primitive heart tube and how it is put in the right place in the body plan

Answer 3

Lateral folding brings the blood islands of the cardiogenic region together to form the primitive heart tube

Cephalocaudal folding then pulls this and the pericardial cavity down into the thorax

Question 4

Starting from the region where blood flows in in the embryo, name the 6 regions of the primitive heart tube

Answer 4

Sinus venosus->atrium->ventricle->bulbus cordis-> truncus arteriosus->aortic roots

Question 5

Cardiac looping pushes the atria up and behind the primitive ventricle and ensures the inflow and our life are in the correct orientation. What days does cardiac looping begin?

Answer 5

Day 23

Question 6

Cardiac looping also ensures that the arteries lie central to the veins, and creates what passageway?

Answer 6

The transverse pericardial sinus

Question 7

Venous return to the sinus venosus initially is equal from the left and right dorsal horns, which horn recedes and what does the remaining horn become?

Answer 7

Left sinus horn recedes

Right sinus horn is absorbed by growing right atria and becomes part of the right atrial wall

Question 8

What are the two venous drainages to the right atrium in a mature adult?

Answer 8

Vena cava (body)
Coronary sinus (heart)

Question 9

What two parts of the primitive heart tube form the mature right atrium?

Answer 9

Most of the primitive atrium and the sinus venosus

Explanation - the absorption of the sinus venosus explains how the RA gets the systemic blood supply

Question 10

Describe the formation of the mature LA from the primordial one

Answer 10

1) pulmonary vein sprouts from primordial LA
2) mature LA formed from walls of pulmonary vein
3) remnants of primordial LA forms the left auricle

Question 11

Describe the feral circulation starting with the maternal oxygenated blood entering from the placenta and then going to the inferior vena cava via the ductus venosus

Answer 11

Enters right atrium (some leaks into RV and is shunted via ductus arteriosus to aorta) -> shunted to left atrium through foramen ovale -> LV -> aorta -> body -> placenta -> ductus venosus -> IVC -> RA

Question 12

Some of the blood from the left atrium isn’t successfully shunted to the right atrium, this then goes into the region ventricle, which shunt is responsible for carrying this directly to the aorta so it doesn’t go to the lungs and disrupt development?

Answer 12

Ductus arteriosus

Question 13

When a baby takes its first breath two shunts close, which ones and how does this happen?

How does the ductus venosus close?

Answer 13

LA pressure increases and seals the foramen ovale shut
Ductus arteriosus contracts and shuts

Closes when the placental support is removed

Question 14

Each arterial system is remodelled from a set of arches. How many aortic arches are there?

Answer 14

6

Question 15

What are the derivatives of the right and left 4th arches

Answer 15

R - proximal part of right subclavian artery

L- arch of aorta

Question 16

What are the derivatives of the left and right portions of the 6th aortic arch

Answer 16

R = right pulmonary artery 
L = left pulmonary artery and ductus arteriosus

Question 17

As the heart descends in cephalocaudal folding a nerve hooks around the 6th aortic arch. What is the name of the nerve this will become?

Answer 17

Left recurrent laryngeal nerve

Question 18

PDA is an arterial system defect in which wHat shunt doesn’t close?

Answer 18

Ductus arteriosus

Question 19

What structure forms after cardiac looping to link the atria and ventricle?

Answer 19

Atrioventricular canal

Question 20

What the three functions of cardiac looping?

Answer 20

Correctly orientates the bloodflow tracts/pushes the atria up and behind the ventricle/creates the transverce pericardial sinus