Embryonic cardiac development Flashcards
Where does the heart begin to develop?
Cranial to the oropharyngeal membrane in the viscer layer of the lateral plate mesoderm to form a horseshoe shape around the neural plate, this is the primary heart field
Occurs during gastrulation
What induces the primary heart field to differentiate?
NKX 2.5 (Tinman gene in fruit flies)
What cells migrate to form the secondary heart frield?
Mesoderm cells under the pharynx
What are the structures of the secondary heart field?
The outflow region and inflow (once the fetal heart has formed the endothelial tube)
Right ventricle, outflow tract and small parts of both atria
What are the structures of the primary heart field?
Left ventricle and most of both atria
What gene is responsible for patterning the heart progenitor cells?
PITX 2 (laterality master gene)
When the heart cells of the primary heart field begin to coalesce, what structure is formed?
Endothelial tube - forms during lateral body wall folding
What external structure contains the aortic arches?
The pharyngeal arches
Five well developed aortic arches
What brings the heart into the thoracic cavity during embryonic development?
Cranial formation
Overgrowth of neural folds and ventral body folding
What forms the septum transversum?
The visceral lateral plate mesoderm where the heart progenitor cells first migrated to form the primary heart field.
What creates the typical heart shape from the cardiac tube?
Cardiac looping (looping begins at ~28 days and typical heart established at 4.5 wks)
NODAL & LEFTY2 upregulate PITX2for extracellular matrix deposition
NKX2.5 upregulates HAND1 & HAND2HAND1 = left ventricleHAND2 = right ventricle
When do the atria definitively form?
When venous blood flow shifts from left to right
The left common cardinal vein merges with the right. The left sinus horn becomes the coronary sinus which terminates as the oblique vein of the left atrium. The right sinus horn expands into the atrium
What expands the right and left atria?
The incorporation of the right sinus horn into the right atrium
The incorporation of the pulmonary vein into the left atrium
How do the pulmonary veins develop?
The septum premeum pulls the dorsal mesocardium down to septate the atria - mesoderm from the mesentery that connects the heart to the gut tube
Why is the dorsal mesocardium important in development of the heart?
The pulmonary veins develop in this mesentery tissue
What septates the heart?
The endocardial cushions
Fetal blood flow
Placenta - Umbilical vein - inferior vena cava - oval foramen - left atrium - left ventricle - aorta
Some blood gets into the left atrium and left ventricle to continue growing the lungs, but is again bypassed at the pulmonary artery by the ductus arteriosis
Lungs (foramen ovale) and liver (ductus venosus) are bypassed
After the atria are septated, how does blood get across to the left atrium?
Programmed cell death creates the ostium secundum to create blood flow between the right and left atria.
After the formation of the septum secundum, how does blood flow from the right to left atria?
The foramen ovale
The septum premum becomes the valve of the foramen ovale
What leads to Epstein anomaly?
Signaling in laterality
In people with Ebstein anomaly, the leaflets are placed deeper into the right ventricle instead of the normal position. The leaflets are often larger than normal. The defect most often causes the valve to work poorly, and blood may go the wrong way. Instead of flowing out to the lungs, the blood flows back into the right atrium.
