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
What cells are the endocardial cushions derived from in the AV canal and the outflow tract?
AV canal - enothelial cells (endocardium)
Outflow tract - neural crest cells
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
What septates the atria?
The descension of the septum premum
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 forms the nonmuscular portion of the interventricular septum?
Endocardial cushions
What become the valves of the atrioventricular canals?
The endocardial cushions
What is the ligamentum stenosum?
After the umbilical cord is clamped, the ductus venosus closes and becomes fibrous.
What is the ligamentum teres?
The umbilical vein after it closes down (after birth)
What causes the foramen ovale to close after birth?
The pressure change due to inspiration
This process of closing the foramen ovale takes about a month (10% of people do not close)
What causes the ductus arteriosis to close?
Bradychinin from the lungs signals the musculature to close
Forms ligamentum arteriosum
tricuspid valve
Between right atrium and ventricle
What prevents valve prolaps in the heart?
Papillary muscles connect to the chordae tendineae
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.
What are the regions of the outflow tract?
(Fetal heart development)
The proximal region - conus
Distal region - truncus
Endocardial cushions form at both regions = derived from neural crest cells
What happens if the endocardial cushions of the conus and truncus do not spiral during development?
The pulmonary artery comes out of the left ventricle and aorta comes out of the right ventricle
The formation of these endo
What does the third aortic arch form?
The carotid
What does fourth aortic arch form?
The aorta
What does the sixth aortic arch form?
The pulmonary artery
