Heart Development

Question 1

The embryological origins of the heart are:

Answer 1

Splanchnic layer of lateral plate mesoderm.

Neural crest cells (mesenchyme).

Question 2

Primary heart fields develop into:

Answer 2

LA, RA, LV

Question 3

Secondary heart fields develop into:

Answer 3

RV and outflow tract.

Question 4

Endocardial heart tubes vs. dorsal aorta

Answer 4

Endocardial heart tubes is the primitive heart. The dorsal aorta lie dorsally.

Question 5

Dorsal mesocardium

Answer 5

Mesentery (double layer of splanchnic mesoderm) that carries BVs, lymphatics and nerves.
Degenerates to become transverse pericardial sinus, which separates the inflow from outflow tracts.

Question 6

Neural crest contributions

Answer 6

NC from myelencephalon migrate thru PA 3,4,6.

Participate in formation of truncus arteriosus and aorticopulmonary septa.

Question 7

Affects of retinoic acid, Hox genes, Nf-1 and Pax-3 on NC cells

Answer 7

They regulate NC migration.

Irregularities can cause CVS defects.

Question 8

Formation of the primitive heart

Answer 8

Endocardial tubes fuse.
Truncus arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus

Question 9

Heart folding

Answer 9

Bulbus cordis and ventricles grow quickly and cause a RH turn (bulbuventricular loop) so that the ventricles face anteriorly and slump downward.

Question 10

Bulbus cordis and truncus arteriosus becomes:

Answer 10

Aorta and pulmonary trunk

Question 11

When do septation events occur?

Answer 11

Mid 4th week and end during the 8th week.

Mesenchyme comes in during 5th week.

Question 12

AV canal septation

Answer 12

Endocardial (AV) cushions from growth from dorsla and ventral walls grow together.
Results in right and left AV canals and separate atria from ventricles.

Question 13

Disruption of retinoic acid signaling mostly produces:

Answer 13

AV canal defects

Question 14

Right horn of the sinus venosus:

Answer 14

Incorporated into the wall of the atrium and becomes sinus venarum. Also forms the orifices of the SVC/IVC and coronary sinus.

Question 15

Pectinate m. is from:

Answer 15

Primitive heart tubes

Question 16

Left horn of the sinus venosus:

Answer 16

Is remodeled to form the coronary sinus.

Question 17

Cranially, the left and right sinuatrial valves fuse with:

Answer 17

Septum spurium

Question 18

Cranially, the right sinuatrial valve becomes:

Answer 18

Crista terminalis

Question 19

Caudally, the right sinuatrial valve becomes:

Answer 19

Valve of coronary sinus and valve of the IVC.

Question 20

Atrial septation

Answer 20

Septum primum forms and creates a small foramen primum. Before foramen primum meets with the endocardial cushion, apoptosis creates a foramen secundum. Septum secundum forms and overlaps with septum primum and includes foramen ovael which allows blood to flow from RA to LA.

Question 21

Septation of the muscular part of the ventricles:

Answer 21

Interventricular septum grows superiorly and leaves a small opening between it and the endocardial cushion. This is the interventricular foramen.

Question 22

Septation of the bulbus cordis and truncus arteriosus

Answer 22

NC cells from PA 4 and 6 migrate into TA and BC and form ridges. 180 degree spiraling occurs.
Creates a aorticopulmonary septum that divides bulbus cordis and truncus arteriosus into ascending aorta and pulmonary trunk

Question 23

Bulbus cordis on the right gives rise to:

On the left:

Answer 23

Conus arteriosus (infundibulum)
Aortic vestibule

Question 24

Finishing IV septation

Answer 24

Membranous IV septum formed by ingrowth of endocardial cushion, right and left bulbar ridges. Complete fusion causes disappearance of IV foramen.

Question 25

Cardiac valves development

Answer 25

Formed between BC and TA.
Valve swellings occur causing the sides to grow together.
Blood is already being pumped so as it goes past the valve it backflows and erodes to form cusps.