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Embryology of heart (Fetal heart (23 -28 (Fold + loop differiential growth…
Embryology of heart
Fetal heart
23
Blood from yolk sac, body + placenta enter sinus venosus (caudal end) passes out aortic roots at cranial end
23 -28
- Fold + loop differiential growth
- Cephallic end bends right and moves ventrally and caudally relative to sinus venosus: moves cephallad and dorsally
- Folding of heart tube 6 days
- Bulbis cordis and ventricle grow faster than rest of heart
Fold onto itself U shape bulboventricular loop
- Keeps expanding S shaped loop
- Atrium and sinus venous pushed dorsally
- Heart tube continues to elongate and bend: filling pericardial cavity
- Truncus arteriosus
- Left atrium
- Left ventrincle
- Right ventricle
- Conus cordis
- Right atrium
Truncus arteriosus: Continuous with aortic sac (arches)
Sinus Venosus: receives umbilical, vitelline and cardinal veins
- Endothelial strands: (angioblastic cords) 3rd week: FORM 2 endocardial heart tubes
- Lateral folding of embryo fuses 2 tubes into 1 ENDOCARDIAL TUBE
- Pericardial cavity around tube
- Tube elongates and develops alternate dilations and constrictions
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Embryology
Mesoderm
Connective tissue, muscle, mesothelium
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Blood flow
- Blood drains into right atrium
- Through foramen ovale
- left atrium
- Left ventricle
- Aorta
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Blood flow fetal heart
28
- Blood flow common atrium
- AVT canal into primitive left ventricle
- Interventricular foramen
- Primitive right ventricle
- bulbus cordis (Conus cordis and truncus arteriosus)
Atrial septum:
Septum primum (first wall) : grows from the roof of atrium
- foramen primum Gap at bottom allows blood to flow from right to left
- Before septum completely blocks the areas of atria, second hole forms (foramen secundum) higher up in septum
Septum primum:
- Fibrous
- Muscular
- Cartilaginous
- Adipose
Chambers connected by common AV canal
- Endocardial cushions develop superiorily and inferiorily, divide canal separate right + left atrioventricular orifices
(go onto become mitral and tricuspid)
- Second wall starts grow down from atrium: septum secundum : fetal life, septa create shunt bypass lungs: FORAMEN OVALE
After birth pressure in left side greater
Septum primum pushes against septum secundum: fuse: leave indentation: FOSSA OVALE
INTERVENTRICULAR SEPTUM: LEFT AND RIGHT VENTRICLES
- Final part : membranous part of IV septum
- Proliferation of myoblasts grow septum upwards towards endocardial cushions
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Ductus venosus
- Approaching liver, half blood through ductus venosus. Rest travels through liver, through sinusoids + hepatic veins and IVC
- Ductus venosus fetal vessel connects umbilical vein to IVC (bypassing liver)
- Blood flow regulated sphincter mechanism close to umbilical vein
- Relax: blood ductus venosus
Umbilical vein
- Highly oxygenated + nutrient rich blood from placenta through umbilical vein in umbilical cord
- Ligamentum teres of liver adult remnant
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