CVS-embryology Flashcards
What day does the formation of the heart begin?
Week 3/ 18 days
When is the first heartbeat heard?
Week 4 /day 22
where do endocardial heart tubes form?
on each side of the heart tube
what does folding of heart tubes do?
brings them together-they fuse into a single heart tube
what are the 5 regions of the heart tube?
- sinus venosus (venous flow)
- primitive atrium
- primitive ventricle
- bulbus cordis
- truncus arteriosus (aterial flow)
which structures does the truncus arteriosus become?
ascending aorta
pulmonary trunk
what does the bulbus cordis become?
right ventricle
what does the primitive ventricle become?
left ventricle
which structures does the primitive atrium become?
RA , anterior wall LA, right auricle, left auricle
which structures does the sinus venosus become?
posterior wall RA, coronary sinus, SA node
where does the heart develop from?
the mesoderm
describe how the heart folds
1-heart tube folds + regions grow → ventricle and bulbus cordis grow most
2-ventricle grows most → causes deepening of bulboventricular groove and appearance of atrioventricular groove
3-Folding of heart tube gives shape of adult heart
4-Now needs to be partitioned internally to separate single tube into 4 chambers
in what week on development do the endocardial cushions form?
week 5
describe the events which occur in week 5-7 of development
1-formation of endocardial cushions
2-partitioning of atrium
3-partitioning of ventricle
4-partitioning of bulbus cordis and truncus ateriorsus
what does the formation of endocardial cushions do?
-splits atrium from ventricle
which structures do the endocardial cushions eventually become?
AV valves
what does the partitioning of the atrium do?
splits single atrium into left and right
what does the partitioning of the ventricle do?
splits single ventricle into left and right
what does the partitioning of the bulbus cordis and truncus arteriosus do?
split into aorta and pulmonary trunk
outline the steps in the partitioning of the atria.
- septum primum forms, with a hole inside = foramen primum
- As foramen primum is closing, apoptosis occurs further up septum primum
- Now foramen primum is closed, and foramen secundum is formed as a result of apoptosis
- septum secundum forms in RA, with another hole – foramen ovale → Blood flows between the two atria through these holes
in new borns what happens to the septum primum and secundum?
forced together, due to increased pressure in atria = holes close
what is the name if the septum which splits aorta from pulmonary trunk?
aorticopulmonary septum
why is there a 180 degree rotation of the truncus arteriosus?
so that the pulmonary trunk sits anteriorly and the aorta, posteriorly
what is the role of the sinus venosus?
directs venous inflow into heart – has right and left horn
what does the left horn of sinus venosus become?
Regresses to become the coronary sinus
what does the right horn of sinus venosus become?
Enlarges to become part of the SVC and right atrium
name the 3 vascular shunts in foetal circulation
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
what does the ductus venosus bypass?
liver
what does the foramem ovale bypass?
lungs (blood travels from RA to LA)
what does the ductus arteriosus bypass?
lungs (blood travels from pulmonary trunk to aorta)
what is different about foetal Hb?
- Has much higher affinity for O2 binding than adult haemoglobin
- Becomes saturated at lower pO2
(due to o2 availability being much lower in foetus than adult)
at which age does foetal Hb change to adult?
within 6 months as site of haematopoiesis changes
what causes the foramen ovale to close?
- increased blood flow into LA from pulmonary veins raises pressure in LA
- causes flap to close
when should the foramen ovale fuse?
~3 months
what is the remnant of foramen ovale called in adults?
fossa ovalis
how is the ductus arteriosus kept open in a foetus?
- prostaglandins (PGE2 and PGE1) secreted by placenta
- this inhibits vasoconstriction of ductus arteriosus and keeps it patent (open/unobstructed) as a shunt
what causes the ductus arteriosus to close after birth?
- PGE2 and PGE1 levels drop
- ductus arteriosus vasoconstricts until lumen is closed
what is the remnant of ductus arteriosus in adults?
ligamentum arteriosum
how does the ductus venosus close after birth?
- PGE2 and PGE1 levels drop
- sphincter contracts around DV = forces blood into liver sinusoids
- Empty DV closes/fuses
what is the remnant of ductus venosus in adults?
ligamentum venosum
–>in posterior view LV is between L and R lobes
what is an example of an atrial septal defect (ASDs)?
-patent foramen ovale
(hole in heart)
–>most common ASD
what are examples of ventricular septal defects (VSDs)?
- partial absence of ventricular septum
- > reasonably common
- complete absence of septum
- > very rare
