Mod 4 Embryology
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What are the 5 important parts of the tube that will eventually form the heart?
- 1) outflow tracts (aorta and pulm artery)
- 2) bulbus cordis (rt ventricle)
- 3) ventricle (Lt. ventricle)
- 4) atrium (L and R atrium)
- 5) sinus venosus (inflow to atria, left side mostly disappears (becomes coronary sinus), right side remains and becomes vena cavae)
Describe the embryological basis for atrial septal defects
- failure of septum secondum to completely cover ostium secondum
- incomplete partitioning of the atria
describe the embryological basis of atrioventricular septal defects
- failure of endocardial cushions to fuse: septum primum cant develop, I/V septum cant close, improper formation of valves
- results in a left to right shunt and congestive heart failure
What are the possible embryological origins of ventricular septal defects?
- Incomplete growth of I/V septum
- small perforations in I/V septum
- abnormal development of truncus arteriosus swellings
- atrioventricular septal defects
What is the embryological cause of persistent truncus arteriosus
- failed septation of TA
- right and left circulation enter a common outflow tract
- cyanotic disease
What is the embryological origin of transposition of the great vessels
- no spiral growth in trunctus arteriosus
- creates two closed loops
- fatal: ductus arteriosus will keep infant alive for a little while
What are the 4 concurrent malformations of the tetralogy of fallot?
- pulmonary valve stenosis
- overriding aorta
- ventricular septal defect
- right ventricle hypertrophy
Name and describe the 3 fetal vascular shunts
- ductus venosus: shunts most blood past liver and to IVC
- foramen ovale: shunts most blood from RA to LA
- ductus arteriosus: shunts blood from the pulmonary trunk to the aorta
What circulatory changes happen at birth
- vasodilation of lung vessels/constriction of ductus arteriosus (more flow to lungs)
- constriction of umbilical arteries (decrease of flow from these arteries)
- increase of flow to lungs closes foramen ovale
- closure of ductus venosus increases systemic circ resistance
What CV changes happen to a mother in pregnancy?
- The rules of 40%:
- -40% increase in blood volume
- -40% increase in CO
- -a further 40% increase in CO in labour
- Blood can more easily clot
- Blood pressure WILL not increase (increase in CO is compensated by a decrease in systemic vascular resistance)
Where does hematopoiesis happen in the fetus?
- before 5 weeks: yolk sac
- after week 5: mostly in liver
- ultimately bone marrow will take over
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