Lecture 19: Heart embryology Flashcards
How does the heart tube develop?
from the fusion of the paired heart tubes that arise from the angioblastic cords
path of blood flow through single tube heart, from cranial to caudal
sinus venosus–>sinoatrial valve –> primitive atrium,–>atrioventricular canal –> primitive ventricle, –>bulbus cordis, –>truncus arteriosis, –> aortic sac,
What is cardiogenic mesoderm
Mesoderm that migrated cranial to the pre-chordal plate during formation of the primitive groove
position of angioblastic cords
directly adjacent to the intra-embryonic coelem
fate of angioblastic cords
eventually form paired heart tubes/aorta, which fuse to form single dorsal aorta and single tube heart
initial position of cardiogenic mesoderm
Cranial to pre-chordal plate, near septum transversum and head of horseshoe part of intra-embryonic coelem. During cranial caudal folding migrates towards the chest, along with those associated structures.
fate of blood islands
form network of arteries and veins within the yolk sac connected to rest of circulation through the vitelline arteries and veins
umbilical artery and vein
connect the chrionic sac/maternal circulation to dorsal aorta (umbilical artery) and sinus venosus (umbilical vein)
What does the fetal circulation lack, notably
circulation through the lungs
What causes the heart to fold
- more dominent proliferation on one side 2. aided by cranial caudal folding
function of fusing AV endocardial cushions
Creates a left and right side of the heart/ left and right AV canals, separates atria from ventricles, fused endocardial cushion plays a role in the formation of mitral valve and tricuspid valve
What forms during heart folding
fused endocardial cushion, primordial IV septum, septum primus
How does Interventricular (IV) septum form
myocardium grows from the the bottom wall between the two ventricles towards the indocardial cushion, while a membranous septum grows down from the endocardial cushion and joins the muscular outgrowth.
ventriculoseptal defect
the most common cardiac defect, found in the membranous septum tissue between ventricles. Most of the time will close naturally
functions of papillary muscle
holds AV valves down, stop them from pro-lapsing (folding back into the atrias) when the ventricles contract.
septum primums
grows down from wall of atrium, towards endocardial tissue. Eventually meets endocardial tissue. Has foramen secundum permanently in it. After formation of foramen secundum top part of septum primum degenerates
foramen primum
hole that forms between the septum primum and endocardial cushion to allow blood to flow from right atrium to left atrium, just by virtue of the septum primum not reaching all the way down to the cushion. will eventually close during development/growth of septum
foramen secundum
Formed from little perforations in the septum primum that coalesce to form a hole further up in the septum from the foramen primum. this one remains open. After formation top part of foramen primum degenerates
septum secundum
the second septum grows more anterior to the septum down from the ceiling of the atrium towards the endocardial tissue, stops short of the endocardial cushion, over-laps slightly from septum primum extending up from endocardial cushion
Oval foramen
hole that is between the septum primum and septum secundum, which could overlap but are not connected to each other. Between left and right atria.
what makes up the valve of the oval foramen
the septum primum and septum secundum. the opening is in secundum, flap that covers it up is primum (what moves in rxn to blood pressure). these eventually fuse after birth to create inter-atrial septum. some people will still have holes in their heart
Foramen Ovale
blood bypasses the lung, acts as a shunt between the right and left atria
What causes the foramen ovale to close
the left atrial pressure increases, pulmonary vascular resistance decreases (loss of pulmonary fluid after birth)
left vs. right ventricular outflow tracts
left ventricular outflow –> aorta
right ventricular outflow –> pulmonary artery
Where do conotruncal ridges form
two ridges in the truncus arteriosis and the bulbus cordis, one from each opposite sides of the vessel wall, grow towards each other to meet in the middle while also spiralling around each other 180 degrees
What do the conotruncal ridges fuse to form
the aorticopulmonary septum between primordial aorta and pulmonary artery. The aorticopulmonary septum joins with the interventricular septum
how do the pulmonary and aorta position with respect to each other
they twist 180 degrees as they grow towards each other. This causes the mature anatomy of the pulmonary artery from being anterior at the root, then posterior to the arch, and the anterior to the descending aorta.
semilunar valves
found in aorta and pulmonary artery
formation of semilunar valves
created from 3 subendocardial swellings, which were remodeled to form three thin walled cusps
the atrioventricular (AV) valves
The mitral and tricuspid valves
formation of AV valves
develop from proliferation of tissue around endocardial cushion/AV canals
what does the dorsal aorta rise from
a pair of tubes formed from angioblastic cords, a pair of dorsal aorta are formed, there would be two visible in the cross section
What does the dorsal aorta do
Connects to the aortic arches, which arise from the aortic sac
Where do the aortic arches come from?
They come from the arteries associated with the pharyngeal arches. Six aortic arches develop, each one paired to it’s own pharyngeal arch. Each arch has left and right side that arises from central aortic sac and ends in either the left or right dorsal aorta.
what does the 3. aortic arches develop into mature structures
r. and l. 3 –> r. and l. common carotid artery
what does 6 aortic arch develop into
the l. 6 aortic arch gives rise to the left pulmonary artery and ductus arteriosus, and the right pulmonary artery comes from the r. 6 aortic arch
what does the 4 aortic arch develop into
l. 4th –> significant part of the aortic arch,
r. 4th –> prox r. subclavian artery
what are the cardiac veins
vitelline veins from yolk sac (low O2) umbilical veins (high O2) common cardinal veins from embryo body (low O2)
where do the cardiac veins dump into
the sinus venosus
Does everyone have the same veinous set-up
no, highly variable vessel connection pattern between individuals
how many umbilical veins are there initially
two, but only the left one persists, right one disappears
how does blood flow from the placenta
oxygenated blood flows from the placenta through the umbilical vein, then through the ductus venosus in the liver to bypass passing through the liver before the oxygenated blood goes to the heart
Tetralogy of fallot four factors
pulmonary stenosis, ventricular septal defect, overriding aorta, right ventricular hypertrophy, caused by unequal partitioning of the truncus arteriosis by the conotruncal ridges
tetralogy of fallot, why pulmonary stenosis?
because of unequal partitioning of the truncus arteriosis
tetralogy of fallot, why ventricular septal defect
the aortic wall did not join up with the interventricular septum
tetralogy of fallot, why right ventricular hypertrophy
the right ventrical needs to pump against a lot of resistance (the stenosis of R. pulmonary artery)
