Flashcards in 9/1 Embryology of the heart Deck (44):
what is the termonology of embriology that is different from med.
the cranial or superior is the anterior in embryo; the tail or caudal is posterior in embrio
why do we care about cardio development?
most common birht defects. the leading cause of infant morality.
what is one of the unique properites of circulation
it is always needed and the needs change constantly and must be adapted to the living being as it changes from a tube to two chamber to a four chamber
how is vasculogeniss accomplished
this is accomplished through the molecules FGF2 and VEGF and comes from a blood island (starts with mesodermal cells
how is angiogenesis accomplished
depends on VEGF and is the branching and elaboration of existing vesicles, and builds from what is already there.
what are blood islands?
angiogenic cell clusters (should be vasculogenic) they are where vessels come from
what is the significance of blood islands
they will give vessels and the heart
where are the blood islands located
in the embryonic disc (spanchinic nesoderm) ; the chorionic somatic mesoderm.. ; conentinc stalk somatic mesoderm; yolk sac
what is the layer of cells that contains the blood islands in a horse shoe shape?
the heart starts out as a horse shoe of blood islands near the top, and cranial to the head. this is the splanchinc mesoderm.
Describe how the primordial heart gets to the thorax region:
head fold: bring the heart primordial to the thorax
how do lateral body folds affect the heart development?
brings the paired heart primordia together at the midline where they fuse
how do we get a cental tube of heart at the ventral midline
at 22 days the endocardial tube folds in and fuses to make the tube in the middle with the endocardial inside then the cardiac jelly, then the myocardium on the outside
what are the layers of the heart?
endocardium; cardiac jelly; and the myocardium; epicardium;
inner most endothelial layer and continuous to the endothelial lining of the vasulature
extrcellular matrix and gives rise to the valves
outer muscular layer.
outer most layer, derived from the cells that migrate in from the septum transversum and form the coronary arteriers, include the endothelial lining and smooth muscle.
where is the gut located in a cross section of the embrio
below the notochord and above the heart
where is the spanchnic mesoderm
it lines below the GI tract and arose from the lateral plate mesoderm that splits open to give the spanchnic mesoderm
what will lead to the orientation of the heart?
cardiac looping which is coordinated with the left right orientation of the rest of the body.
how does cardiac looping work?
the heart will make an s curve where the ventricle starts at the cranial and then twists around the antrium and will end in the caudle position.
where does the heart fuse into one tube
where do the antrium start in a sinble tube heart
the antrium starts at the bottom and then twists counterclockwise around to end up towards the top (this is looking ventral to the left, and dorsal to the right in a side-on view.
describe the orientation of the primitive tube heart
the RA and LA in a branch at the bottom of the heart, then the LV in the middle bottom, and the RV in the middle and the Outflow at the top (called the CT).
what happans at the end of looping
the Atrium is at the top and the ventral is at the bottom and there are only those two chambers.
how does the primitive twisted tube heart start to separate into separate ventricles?
a cushion of cells starts to form in common atrioventricular canal. A superior endocardial cushion and an inferior one (small lateral cushions form as well). These cushions fuse together to form seperat right and left atrioventricular canals through the heart.
how do we make the endocardial cushions?
the cells from the endothelium are induced by myocardium to migrate into the cardiac jelly
what is the importance of the endocardial cushion
it will form the valves
how are the left and right atrium separated in the primitive atrium?
the septum premium grows between the two, nearly occluding the ostium primum that forms (which would prevent the outflow of heart form the right atrium). as the ostium primum closes, programed cell death opens up the osmium secundum. as the secundum opens, the septum secundum grows and leaves a hole called the foramen ovale.
why are the foramen ovale and the ostium secundum offset?
to provide a primitive check valve to prevent back flow to the right atrium! (the primum is flexible and the secundum is not)
what is the froaman ovale
the second hole formed and it is formed in the septum secondum.
what is the muscular ventricular septum.
the beginging of the division of the right and left ventricle form the bottom of the heart up (the division will be completed during outflow track septation)
what forms the valves in the heart?
atrioventricular canals form valves through mesodermal proliferation in the myocardium. (the tissue under this build up then atrophies and you get thin flaps or valves.
how do the neural crest cells contribute to the development of the heart
outflow track septation! therefore look for defects in outflow tract septation associated with defects in neural development.
where do the neural crest cells come from to migrat to the heart
from the hind brane and arches 3,4,6
why would a neural defect depentdent on the neural crest cells contribute to heart defects
the migration of neural crest cells to form the outflow septation.
how do the two different paths out of the heart form?
from neural crest cell cushoins or ridges that from in a spiral on the single out flow tract and shunt blood from each ventricle into different paths.
How do we devide the ventricle into two chambers?
by haveing the twisting ridges fuse together and fuse to the muscular ridge on the bottom of the heart. i.e. the conotruncal septa fuse with the interventricular septum!
highlight the changes in blood flow after birth
the oval foramen closes immediately, as well as the ductus venosus, ductus arteriosis and placental vessels closing within minutes.
What: Atresia of tricuspid on right (no valve on right and very little atrium) closure of the oval foramen will shut down circulation (no where for the right atrium to go),
Persistent Truncus Arteriosus
the ventricles don’t seperate because the outlow track fails to seperate out. No pulmonary semi-lunar valve. mixed blood to both the body and the lungs at the same time with every pump.
Transposition of Great arteries
the aorta and the pulmonary artery go to the wrong ventricles. From a failure to spiral out the outflow seperation, ok before birth because of the ductus arteriosus to shunt blood to the right artery
Pulmonary valvular atresia
no pulmonary semilunar valve, the right ventricle atrophies, tolerated before birth because of ductus arteriosus and the oval foramen to shunt blood to the left side and to the lungs.