Development of the Heart

Question 1

Which cardiac structures are populated by second heart field (SHF) cells?

Answer 1

The SHF contributes to the right ventricle and the elongation of the outflow tract (conus/bulbis cordis and truncus arteriosus)

Question 2

Paired endocardial tubes fuse to form what developing structure?

Answer 2

The primitive heart tube

Question 3

_______ results when the heart loops to the left side instead of the right, further resulting in the apex of the heart being located on the right side of the body.

Answer 3

Dextrocardia

Question 4

The reversal of some organs is called __________, while the reversal of all viscera is called ___________

Answer 4

Partial situs ambiguus

Situs inversus totalis

Question 5

The region of the primitive heart tube that forms the roots of the aorta and pulmonary artery is called the _________.

Answer 5

Truncus arteriosus

Question 6

What structure allows blood to flow between the left ad right atria once the ostium primum has closed?

Answer 6

The ostium secundum opens before the ostium primum closes to allow interatrial blood flow to continue…next an opening in the developing septum secundum, called the foramen ovale, allows blood to flow through the foramen ovale and the ostium secundum for the rest of fetal development

Question 7

What condition results from the failure of the foramen ovale to close at birth?

Answer 7

Patent foramen ovale.

It is estimated that 25% of the population has a patent foramen ovale….it is a small atrial septal defect (ASD) that has little clinical significance

Question 8

Describe the three changes in the pattern of circulation that occur after birth

Answer 8

1. Closure of the ductus arteriosus to facilitate blood flow to lungs
2. Closure of foramen ovale when septum primim is pressed against the septum secundum to eliminate interatrial blood exchange
3. Closure of abmilical arteries, umbilical vein, and ductus venosus

Question 9

What is the embryonic origin of VSDs?

Answer 9

VSD: Ventricular septal defects: often result from the failure of the muscular and membranous portions of the interventricular septum to fuse due to incomplete partitioning of the aorta and pulmonary trunk

Question 10

What is the consequence if the conotruncal septum fails to follow a spiral course, but rather expands straight?

What is this congenital heart malformation called?

Answer 10

The aorta will originate from the right ventricle and the pulmonary artery will originate from the left ventricle.

This is called transposition of the great arteries

Question 11

Small ASD defects may have no significant impact on blood flow…but what are the consequences of large ASDs?

Answer 11

Large ASDs allow oxygenated blood from the left atrium to enter the right atrium, which may lead to enlargement of the right atrium and ventricle (due to increased flow), resulting in atrial arrhythmias later in life. Excessive pulmonary blood flow can cause pulmonary HTN and lead to heart failure over time.

Question 12

Failure of the ductus arteriosus to construct and close off results in shunting of blood from the descending thoracic aorta back into the pulmonary trunk…this is called what?

Answer 12

Patent ductus arteriosus

During fetal life, the ductus arteriosus is kept open in part by circulating prostaglandins

Question 13

The incomplete division of the aorta and the pulmonary trunk is called what? What defect must this also be accompanied by?

Answer 13

Persistent (common) truncus arteriosus, which must be accompanied by an interventricular septal defect since the partitioning of the major vessels occurs simultaneously with the complete of the interventricular septum