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Heart
- 4th week-circulation begins
- 22 days-heart beat
- derived from-splanchnic mesoderm, mesenchyme (N.C.), and angioblastic tissue (mesoderm)
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Folding the Pericardial Cavity
- Splanchnic mesoderm
- -pericardial coelom
- -cardiogenic cord-becomes heart (mesoderm)
- Septum transversum-becomes diaphragm
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Heart Primordia
- Splanchinic mesoderm
- -cardiogenic cord
- -endocardial heart tube (endocardium)-inside lining of heart
- Mesenchyme (N.C.)
- -Myoepicardial mantle (splanchnic mesoderm): includes-
- ---myocardium-cardiac muscle
- ---epicardium (visceral pericardium (adult))-outside
- -Dorsal mesocardium-mesentary-route from n., a., lymph to get to heart and obliterates to form the transverse sinus (space)
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cardiac jelly
connective tissue that stays with the endocardium
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Neural Crest Contribution
- Originate from neural crest in the myelencephalon
- Migrate through pharyngeal arches 3, 4, and 6
- Participate in formation of truncus arteriosus (N.C. and mesoderm) and aortiocpulmonary septa (division between aorta and pulmonary trunk)
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What occurs if mother takes in high Vitamin A
Retinoic acid, Hox genes, Nf-1 and Pax 3 regulate cardia neural crest migration and differentiation
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Heart Formation
- Fusion of endocardial heart tubes (mesoderm)
- Primitive Divisions
- Folding
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Primitive Divisions of Heart
- Truncus arteriosus
- Bulbus cordis (together with truncus arteriosus is outflow trap of aorta and pulmonary trunk)
- Ventricle
- Atrium
- Sinus venosus-inflow trap venous system empty into heart-becomes vena cavas
- *all mesoderm*
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Folding of heart
- Bulbus cordis and ventricles grow quickly
- heart bends on itself
- Bulboventricular loop-bends to the right
- -atrium and sinus venosus come to lie dorsally (in back)
- -ventricle moves down
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Dextrocardia
- rotation in opposite direction of Bulboventricular loop
- baby turns out fine if everything switches
- problem occurs when everything doesn't go same direction
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Primitive veins
- common cardinal-return venous blood from body-enters spinuspinosus (deoxygenated)
- vitelline-embryonic RBC back to heart (deoxygenated)
- umbilical-oxygenated from placenta-enters spinuspinosus
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Septation: Atrioventricular canal
- 2 chamber heart to 4 chamber heart
- Endocardial cushions (mesoderm)
- -dorsal and ventral walls
- -mesenchyme invades (N.C.)
- -cushions grow together
- right and left canals formed
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Septation: Atrium
- Dorsal atria
- Shunt blood from right and lefft
- Septum primum-2 foramen
- Septum secundum
- definitive fetal separation of the atria
- Septum secundum does not completely close, leaving a patent foramen ovale
- Durign the embryonic and fetal life, blood entering the right atrium passes to the left atrium via the foramen ovale and ostium secundum-form shunt
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Septum primum
- Foramen primum
- -shunt between right and left atrium
- -gone when fuses with endocardial chusions
- Foramen secundum
- -forms before foramen primum disappears
- -formation ensures shunting
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Septum secundum
- overlaps septum primum
- foramen ovale
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septation: ventricle
- interventricular septum: muscular portion (mesoderm)
- interventricular foramen
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Septation: Bulbus cordis and Truncus arteriosus
- nerual crest cells form ridges (bulbar and truncal)
- 180 degree spiraling
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Aoricopulmonary septum
- Divides bulbus cordis and truncus arteriosus into ascending aorta and the pulmonary trunk (N.C.)
- Fuses with the endocardial cushion (mesoderm)
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Incorporated bulbus cordis
- Right: conus arteriosus-ventricles (mesoderm)
- Left: aortic vestibule (below semilunar valve)-mesoderm
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Interventricular Septum
- attach to muscular portion in foramen
- membranous interventricular septum
- -endocardial cushion (mesoderm)
- -right bulbar ridge (N.C.)
- -left bulbar ridge (N.C.)
- complete fusion results in teh disappearance of the interventricular foramen
- Defects in septum due to membranous part (N.C.) of the septum
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