Embryonic Structures

Question 1

Name the embryonic structures that make up the right atrium in adults.

Answer 1

1. Sinus venarum
   - from right sinus horn of sinus venosus
2. Atrial auricle
   - from original embryonic atrium

Question 2

What embryonic structure is the precursor for the coronary sinus?

Answer 2

Left sinus horn of sinus venosus

Question 3

What was the precursor for the trabeculated portion of the left ventricle?

Answer 3

Primitive ventricle

Question 4

What forms the trabeculated region of the right ventricle?

Answer 4

caudal portion of bulbus cordis

Question 5

What forms the outflow region for both ventricles?

Answer 5

Conus cordis for both

Conus arteriosus for right ventricle

Aortic vestibule for left ventricle

Question 6

What embryonic structure forms the pulmonary trunk and (ascending) aorta?

Answer 6

Truncus arteriosus

Question 7

What forms the bulk of the interatrial septum?

Answer 7

Septum secundum

Question 8

PFO is a result when what doesn’t fuse completely?

Answer 8

Valve of foramen ovale (septum primum) doesn’t completely fuse to septum secundum

Question 9

What forms AV valves?

Answer 9

Neural crest of endocardial cushions

Question 10

What forms semilunar valves?

Answer 10

Neural crest of conotruncal ridges

Question 11

Which aortic arch arteries regress?

Answer 11

1*, 2, 5

1* forms maxillary aa, which we don’t care about right now

Question 12

What aortic arch arteries go on to form important structures that we care about?

Answer 12

aortic sac, 3, 4, 6, and 7th intersegmental

Question 13

What does the aortic sac form?

Answer 13

proximal portion of aortic arch and brachiocephalic artery

Question 14

What does the third aortic arch form?

Answer 14

Common carotid artery

Question 15

What does the fourth aortic arch form?

Answer 15

Know right from left!

R: R subclavian artery

L: portion of aortic arch

Question 16

What does the sixth aortic arch form?

Answer 16

Know right from left!

R: pulmonary artery

L: pulmonary artery, and ductus arteriosus

Question 17

What does the seventh intersegmental artery form?

Answer 17

Know right from left!

R: distal part of R subclavian

L: L subclavian artery

Question 18

What structure created the ligamentum arteriosum?

Answer 18

Ductus arteriosus

Question 19

What is the relationship of the right recurrent laryngeal nerve to other structures?

Answer 19

Nerve loops around 4th aortic arch
- (aortic arches 5 and distal 6 regress)

4th aortic arch becomes R subclavian

Question 20

What is the relationship of the left recurrent laryngeal nerve to other structures?

Answer 20

Nerve loops around distal part of 6th aortic arch

Arch goes on to become ductus arteriosus

Nerve ends up wrapped around ligamentum arteriosum in adults

Question 21

What structures create the left and right brachiocephalic veins?

Answer 21

Anterior cardinal veins

Question 22

What structure creates the superior vena cava?

Answer 22

Right common cardinal

Question 23

What structure creates the azygos system of veins?

Answer 23

Supracardinal veins

Question 24

What forms the renal portion of the inferior vena cava?

Answer 24

Right subcardinal vein

Question 25

What forms the distal portion of the IVC?

Answer 25

Right Sacrocardinal veins

Question 26

What embryological structures form the left atrium?

Answer 26

1. Smooth-walled portion of atrial chamber
   - from proximal portion of pulmonary vein
2. original embryonic atrium forms the Auricle