Heart Development Flashcards
heart beat begins in ___ week
septation occurs during ___ week
Heart beat begins in 3rd week.
Septation during 4th week.
Must continue to pump blood as it rearranges/develops
causes of heart defects
1) single gene mutations
2) Chromosomal aberrations
3) Neural crest defects/ deficits
4) teratogens
5) diseases
___________ provides tissue for the heart
lateral plate mesoderm
lateral plate mesoderm divides into ________ layer and; _________ layer
[+ what they will form]
Lateral plate mesoderm divides into Somatic layer (parietal pericardium) and; Splanchnic Layer (cardiac muscle, visceral pericardium)
Separated by intraembryonic coelom (will form pericardial cavity)
two pathways of cardiogenic induction
1) vasculogenesis (medial): condensation of mesenchyme to form vessels, blood cells
2) myogenesis (lateral): gives rise to heart muscle
lateral folding of embryo
~3 weeks
Brings 2 heart tubes together to form single tube
rostro-caudal folding of embryo
~3 weeks
Moves developing heart into neck, thorax. Takes nerve supply with it.
Driven by rapid growth of neural tissue.
dorsal mesocardium
Suspends the heart after embryonic folding. Needs to be broken down to:
1) allow heart looping
2) form adult transverse pericardial sinus
absent cilia during heart looping causes
dextrocardia or situs inversus totalis
embryonic veins
1) common cardinal vein
2) vitelline veins
3) umbilical vein
rightward shift of venous flow
Sinus horn becomes coronary sinus.
Left umbilical vein persists.
Vitelline veins become liver sinusoids.
Cardinal veins go elsewhere.
Right umbilical vein becomes ductus venosus to allow maternal blood to join IVC.
Now all blood enters R side of heart
intussusception
Uses wall of sinus venosum (smooth, becomes sinus venarum) to grow R atrial wall (rough pectinate muscles).
Joined at crista terminalis.
Growing pulmonary veins incorporated into L atrial wall.
septation (general)
Endocardial cushions contribute to atrial septa, ventricular septa, aorticopulmonary septum, AV heart valves, AV node.
septum intermedium
Separates 2 AV canals.
Also forms part of interventricular and interatrial septums too (crux).
From inferior/superior endocardial cushions.
Ways to bypass fetal lungs
1) foramen ovale: right atrium to left atrium
2) ductus arteriosus: pulmonary trunk to aorta
atrial septation
1) Growth of septum primum from atrial roof toward septum intermedium. Ostium primum (opening) remains.
2) Opening in upper septum primum (ostium secundum) forms. Ostium primum seals. by fusion with septum intermedium.
3) Septum secundum grows to cover ostium secundum, forming foramen ovale (closed by change in pressure at birth)
ventricular septation
1) myocardial growth forms muscular ventricular septum
2) endocardial cushion tissue growth forms membranous septum
if membranous and muscular ventricular septum do not meet, causes —
atrioventricular septal defect
conotruncal septation
Produces aortic & pulmonary trunks.
Aorticopulmonary septum creates a spiral division.
craniofacial defects at birth might indicate:
neural crest problem
Aorticopulmonary defects also caused by lack of neural crest.
change in blood pressures after birth
Maternal blood is stopped: decrease pressure in RA.
First breath: increases pressure in LA.
Both: shut foramen ovale (forms fossa ovalis)
persistent truncus arteriosus
Failure of conotruncal ridges to fuse.
Causes IV septum defect.
Mixture of venous/arterial blood.
Tx: surgery
transposition of great vessels
Due to failure of conotruncal septum to SPIRAL.
Tx: prostaglandins to keep ductus arteriosus open, surgery
tetralogy of Fallot
Primary defect: anterior displacement of conotruncal septum (unequal division of conotruncus.
Secondary defects: Misalignment of aorticopulmonary + membranous IV septum (IV septal defect). Overriding aorta (mixes oxygenated/deoxygenated blood). Hypertrophy of R ventricle.
