Embryology and Congenital Heart Defects Flashcards
what is the foramen primum?
the foramen between the atrium chambers
before the foramen primum becomes obliterated what appears in the interatrial septum (septum primum)?
foramen secondum
what does the development of the foramen secondum before the foramen primum has been fully obliterated allow?
the uninterrupted shunting of blood from right atrium to left atrium
(foramen secundum takes over the job of the foramen primum)
where does the septum secondum grow in relation to the septum primum which has already formed?
to the right of it
what is the function of the septum secondum?
partially covers the foramen secondum
what is the small hole that appears as the septum secondum partially covers the foramen secondum?
foramen ovale
what acts as a uni-directional flutter valve to ensure that blood flowing through the foramen ovale only moves from the right atrium to the left atrium?
septum primum
what is the truncus arteriosus?
the original shared outflow track of the ventricles
what embrylogical aortic arch forms the aorta?
4th
what embryological aortic arch forms the pulmonary trunk?
6th
what does bifurcation of the truncus arteriosus lead to?
aorta and pulmonary trunk
why are the pulmonary arteries in an embryo constricted?
due to hypoxia in the pulmonary tissue
what are the 2 major way the fetal circulation bypasses the lungs?
foramen ovale
ductus arteriosus
what is the ductus arteriosus?
a connection from the pulmonary artery to the aorta to bypass the lungs
how many umbilical veins is there?
1
how many umbilical arteries are there?
2
what blood does the umbilical vein carry?
oxygenated blood for the foetus
what blood does the umbilical arteries carry?
deoxygenated blood from the foetus
what is the ductus venosus?
a connection from the umbilical vein to the inferior vena cava to bypass the liver
why does the ductus arteriosus close after birth?
- increase in oxygen
2. decreased prostaglandins (which were from mother)
why might the ductus arteriosus remain open after birth?
- poor oxygen exchange (ie premature baby)
- high prostaglandin plasma concentrations
- increased sensitivity to prostaglandins
- rubella infection
what are the clinical signs of a patent ductus arteriosus?
- specific murmur
- widening pulse pressure
- enlarged heart
in a patent ductus arteriosus, which direction does the blood flow through this channel?
from aorta to pulmonary arteries
opposite direction to the way it was going in the foetus
what is the treatment for PDA?
drugs: NSAIDs
surgery: PDA ligation, coil occlusion
why are NSAIDs used in PDA?
they inhibit prostaglandins causing ductus arteriosus to close
what is a patent ductus arteriosus?
a congenital defect where the ductus arteriosus hasn’t closed after birth like it should
what are the defects that make up tetralogy of Fallot? (congenital defect)
pulmonary stenosis
right ventricular hypertrophy
ventricular septal defect
overriding aorta
why is there right ventricular hypertrophy in tetralogy of Fallot?
because of the high resistance (due to the pulmonary stenosis) the right ventricle has to pump against
what is an overriding aorta?
receives blood from both left and right ventricles
ie oxygenated and deoxygenated blood
in tetralogy of Fallot, why is blood from the right ventricle more likely to go to the overriding aorta than the pulmonary trunk?
because of the pulmonary stenosis the pulmonary trunk has a much higher resistance than the aorta
what do kids with tetralogy of Fallot do to relieve their symptoms?
squat suddenly
why does squatting help relieve symptoms of tetralogy fallot?
increase oxygen content in veins
vasoconstriction to increase systemic resistance (less deoxygenated blood goes into the aorta)
what is transposition of the great arteries?
a congenital defect where the aorta and pulmonary trunk are switched,
so deoxygenated blood gets taken to systemic circulation and oygenated blood gets taken to the lungs
(2 completely separate circuits)
what usually comes with transposition of the great arteries?
ventricular septal defect
why is the VSD life sustaining in the congenital defect of transposition of the great ventricles?
allows some oxygenated blood to go to the systemic circulation and some deoxygenated blood to go to the lungs
what is truncus arteriosus?
present after birth
a congenital defect where there is no septum between aorta and pulmonary trunk so deoxygenated blood and oxygenated blood mixes
what is coarction of the aorta?
a congenital defect where there is vasoconstriction just below the subclavian artery
