Flashcards in CV Development: Congenital Heart Dis. Deck (39):
5 major processes that occur in cardiovascular morphogenesis?
Myocardial specification and formation of linear heart tube.
Patterning of great vessels.
Circulatory changes at birth.
Where are the cardiac precursor cells on the embryonic disc?
In the "cardiac crescent"
What connects the linear heart tube to the aorta /other vessels?
The dorsal mesocardium.
Does the early heart make some of its own blood?
We think so.
Are heart chambers pre-specified in the linear heart tube?
Yes, to some extent. (but there's also the secondary heart field)
Where is the "second heart field"?
The second heart field progenitor cells come from the pharynx. (worms have rhythmically contracting guts)
What does looping refer to?
the atria start at the bottom, and loop up to the top.
What's the bulbus cordis?
The region made of the conus cordis (outflow tract) and truncus arteriosis (PA and aorta)
How does the AV canal form?
It's a section of the tube that doesn't grow... so constricted by comparison.
This also forms the endocardial cushions...
What's the first part of atrial septation?
The septum primum forms on the dorsal wall and grows toward the endocardial cushions.
Does the septum primum entirely separate the LA and RA?
Nope, it leaves the ostium primum near the endocardial cushions.
What happens next when there's a septum primum with ostium primum?
Holes form in the dorsal aspect of the septum primum, forming the ostium secundum.
Then the septum secundum passively covers the RA side of the septum primum, covering the ostium secundum in a flap-like fashion.
(the ostium primum fuses shut at some point)
Is the foramen ovale the same thing as the ostium secundum?
Sort of. The foramen ovale is a combination of the ostium secundum and a hole in the septum secundum that allows blood to flow from the RA to LA.
What's the most common atrial septal defect (ASD)?
Persistence of the ostium secundum and/or incomplete formation of the septum secundum.
Patent foramen ovale is a subset of ostium secundum ASD.
What often happens in ostium primum ASD?
There's often a slit-like defect in the anterior leaflet of the mitral valve.
What happens in sinus venosus AV defects?
Defect in formation of septum primum.
Often causes defect in a pulmonary vein such that it comes back to the RA.
What's a homeobox (hox) gene that seems to be particularly significant for causing congenital heart defects in humans?
Why does ASD cause heart block?
People used to think it was due to the holes interfering with conduction...
but really it's more about the impaired development of the specialize conduction cells.
(which can be caused by Nkx2.5 mutations)
What are there, before there are great vessels?
5 pairs of symmetric aortic arches.
Which aortic arch becomes the aorta?
The left 4th aortic arch.
What cells give rise to the aortic arches?
Migrating neural crest cells.
What if both left and right 4th aortic arches degenerate?
It's a problem....
3 organs affected by DeGeorge syndrome?
What, broadly, is the underlying cause?
(What, specifically, is the chromosomal abnormality?)
Heart (congen. defects), parathyroid, and thymus.
Neural crest cells don't function properly.
Deletions on 22q11 cause DeGeorge.
What seems to be the most important gene of 22q11 affected in DeGeorge syndrome?
What happens if the right 4th aortic arch gives rise to the aorta instead of the left 4th aortic arch?
This is called a right-sided aortic arch... which can be fine.
But, it can also cause an aortic ring that can compress the trachea.
What is pulmonary atresia? How can it be survived without surgery, at least early on?
In pulmonary atresia, the PA doesn't form. Blood can still get to the lungs via the ductus arteriosis... but when that obliterates, it's a problem.
What is dextrocardia?
The heart's flipped, so it's on the right....
What is heterotaxy?
When there's discordance in the L-R orientation between organs.
What is thought very early to set up the L-R axis in the embryo?
Cilia that move morphogens in a predictable pattern.
3 abnormalities in Kartagener's syndrome?
What's the underlying cause?
Brochiectasis (airway damage)
-These are all caused by defects in cilia function.
What "phenotypic switch" must happen in the cells that become valves?
Endothelial cells undergo epithelial to mesenchymal transformation (EMT), then migrate into "cardiac jelly" between endothelium and myocardium.
(forming endocardial "cushions")
What's one signaling pathway involved in EMT?
Ras pathway. Defects in Ras signaling -> congenital heart defects involving valve formation.
(Recall: overactive Ras -> oncogenesis)
What's the difference between vasculogenesis and angiogenesis?
Vasculogensis: formation of vessels de novo from endothelial precurosis (angioblasts).
Angiogenesis: Formation of new blood vessels from pre-existing blood vessels.
3 sets of signaling molecules involved in vascular development?
VEGF and VEGF receptors.
Notch ligands and receptors.
Semaphorin ligands and Plexin receptors.
What's interesting about the way Semaphorins guide vasculogenesis/angiogenesis?
Semaphorins are repulsive signals for axon guidance and blood vessel growth.
What gives rise to the epicardium?
The proepicardial organ, from the septum transversum (which also gives rise to diaphragm and liver).
What role does the epicardium play in heart development?
Epicardium induces myocardial maturation.
What do neural crest cells have to do with the outflow tract?
Neural crest cells are necessary for the septation of the truncus arteriosis and cardiac outflow tract