Heart Development Flashcards
The embryological origins of the heart are:
Splanchnic layer of lateral plate mesoderm.
Neural crest cells (mesenchyme).
Primary heart fields develop into:
LA, RA, LV
Secondary heart fields develop into:
RV and outflow tract.
Endocardial heart tubes vs. dorsal aorta
Endocardial heart tubes is the primitive heart. The dorsal aorta lie dorsally.
Dorsal mesocardium
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.
Neural crest contributions
NC from myelencephalon migrate thru PA 3,4,6.
Participate in formation of truncus arteriosus and aorticopulmonary septa.
Affects of retinoic acid, Hox genes, Nf-1 and Pax-3 on NC cells
They regulate NC migration.
Irregularities can cause CVS defects.
Formation of the primitive heart
Endocardial tubes fuse. Truncus arteriosus Bulbus cordis Ventricle Atrium Sinus venosus
Heart folding
Bulbus cordis and ventricles grow quickly and cause a RH turn (bulbuventricular loop) so that the ventricles face anteriorly and slump downward.
Bulbus cordis and truncus arteriosus becomes:
Aorta and pulmonary trunk
When do septation events occur?
Mid 4th week and end during the 8th week.
Mesenchyme comes in during 5th week.
AV canal septation
Endocardial (AV) cushions from growth from dorsla and ventral walls grow together.
Results in right and left AV canals and separate atria from ventricles.
Disruption of retinoic acid signaling mostly produces:
AV canal defects
Right horn of the sinus venosus:
Incorporated into the wall of the atrium and becomes sinus venarum. Also forms the orifices of the SVC/IVC and coronary sinus.
Pectinate m. is from:
Primitive heart tubes
Left horn of the sinus venosus:
Is remodeled to form the coronary sinus.
Cranially, the left and right sinuatrial valves fuse with:
Septum spurium
Cranially, the right sinuatrial valve becomes:
Crista terminalis
Caudally, the right sinuatrial valve becomes:
Valve of coronary sinus and valve of the IVC.
Atrial septation
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.
Septation of the muscular part of the ventricles:
Interventricular septum grows superiorly and leaves a small opening between it and the endocardial cushion. This is the interventricular foramen.
Septation of the bulbus cordis and truncus arteriosus
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
Bulbus cordis on the right gives rise to:
On the left:
Conus arteriosus (infundibulum) Aortic vestibule
Finishing IV septation
Membranous IV septum formed by ingrowth of endocardial cushion, right and left bulbar ridges. Complete fusion causes disappearance of IV foramen.
Cardiac valves development
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.
