Cardio Pt.1

Question 1

Describe the embryonic disc.

Answer 1

-Horse-shoe shaped
-area of blood forming cavities in visceral mesoderm
-forms the primitive heart, blood vessels, and blood cells

Question 2

Describe the folding of the embryonic disc.

Answer 2

1. Horse shoe shaped tubes (endothelial cells only) & then the Endocardial heart tubes make contact with the developing venous system.
2. Caudal portion fuses and becomes surrounded by myoblasts to form myocardium = cardiac tube.
3. Cardiac tube is composed of bulbus cordis (precursor of RV)
4. Ventricle & atrium join venous system
5. Loop formation
6. Division of cardiac tube in 4 chambers = heart

Question 3

Describe the partitioning of the atrio-ventricular canal.

Answer 3

-primitive atrium -> L & R atria
-primitive ventricle -> L & R ventricles
-truncus arteriosus divided into outflow tracts of -> aorta & pulmonary trunk

Question 4

Describe the partitioning of the atrium & ventricle schematic.

Answer 4

1. Primary atrial septum is formed & development of the interventricular septum has begun.
2. Primary atrial septum fused with the endocardial cushions & a secondary foremen has been formed.
3. Secondary atrial formed and a passage (foremen ovale) between primary and secondary septa connects L & R side.
4. Fusion of interventricular septum with endocardial cushion.

Question 5

Describe atrial partitioning.

Answer 5

1. Ostium primum = allows initial passage of blood from R to L atrium as the primary atrial septum grows.
2. When ostium primum closes, it’s replaced by ostium secundum (blood still passes).
3. Secondary septum grows to the right of the primary septum.
4. Primary septum serves as a valve for foremen ovale in secondary septum = prevents return of blood into RA.

Question 6

Describe atrial partitioning after birth.

Answer 6

-lungs expand with first breaths creating sudden BP drop in pulmonary circulation
-pushes primary septum against secondary one = physiological closure of foremen ovale
-fusion & foremen ovale becomes fossa ovalis (anatomical closure)

Question 7

Describe the normal heart development.

Answer 7

-truncus arteriosus gets divided into ascending aorta & pulmonary trunk by a spiral “aortico-pulmonary septum”
-spiral formation of septum ensures blood from RV flows into pulmonary trunk & that the blood from the LV flows into ascending aorta.

Question 8

Describe the abnormal heart development.

Answer 8

-if the septum was straight = transposition of the great vessels
-deoxygenated blood from RV flows into ascending aorta & oxygenated blood from LV flows into pulmonary trunk (lungs)
-fatal

Question 9

What are the 3 blood shunts?

Answer 9

1. Ductus venous
2. Foramen ovale -> fossa ovalis
3. Ductus arteriosus -> ligamentum arteriosum
   all 3 must close after birth