1 - Embryology

Question 1

What are the steps of atrial septum formation?

Answer 1

1) septum primum grows down to the AV cushions; the space between the septum primum and AV cushions is ostium primum
2) the ostium secundum is formed by degeneration of superior part of septum primum
3) septum secundum grows down to the right of septum primum
4) in the septum secundum is the foramen ovale, which allows R->L atrial flow until closed at birth

Question 2

What are the embryonic origins of:

1) aortic/pulmonary trunk
2) smooth R/L ventricular wall
3) trabeculated R/L venticular wall
4) trabeculated R/L atrial wall
5) coronary sinus/smooth atrial wall
6) SVC

Answer 2

1) truncus arteriosus
2) bulbus cordis
3) primitive ventricle
4) primitive atria
5) left/right horn of sinus venosus
6) R common cardinal v., R anterior cardinal v.

Question 3

How is the interventricular septum formed?

Answer 3

1) muscular septum grown upward from base of primitive ventricle toward the AV septum. The resulting gap is interventricular foramen.
2) membranous septum is the fusion of the articopulmonary septum extending down to the muscular septum, obliterating the interventricular foramen

Question 4

How does the aoticopulmonary septum develop?

Answer 4

• migrating neural crest cells accumulate on the conotruncal ridges in the truncus arteriosus
• these grow to bisect the tuncus arteriosus into aortic and pulmonary trunks
• the septum then spirals down to fuse with the ascending muscular interventricular septum to form the R/L ventricle outflow tracks

Question 5

Where is blood made en utero?

Answer 5

Yolk sac - 3-8wks
Liver - 6-30wks
Spleen - 9-28wks
Bone Marrow - >28wks

Question 6

Describe fetal circulation. What changes at birth?

Answer 6

oxygenated blood from placenta -> umbilical vein -> bypass liver via Ductus Venosus -> joins IVC and empties into R.Atrium -> through foramen ovale and “high pressure” pulmonary to L.Atrium (most flow from pulmonary artery bypasses lungs via Ductus Arteriosus)-> L.Ventricle -> aorta -> tissue
Deoxygenated blood from tissue -> umbilical arteries -> placenta

After birth -> Ductus venosus closes, Foramen Ovale closes, pulmonary pressure drops (Pright<Pleft)

Question 7

What do the embryonic aortic arches develop into?

Answer 7

1st - maxillary a.
2nd - stapedial/hyoid a.
3rd - common carotid, internal carotid
4th - AORTIC ARCH, proximal R. subclavian a.
5th - (nothing)
6th - proximal PULMONARY A., DUCTUS ARTERIOSUS

Question 8

What are common genetic disorders and their associated congenital cardiac defects?

Answer 8

22q11 deletion -> truncus arteriosus, Tetrology of Fallot
Down’s -> VSD, ASD, AV septal defect
Turner’s -> coarctation of aorta
diabetic mother -> transposition of great vessels
congenital rubella -> septal defects, PDA, pulmonary stenosis
marfan’s -> aortic insufficiency