3. CVS Development Flashcards
Describe the formation of the primitive heart tube.
Cariogenic field is created during gastrulation, at the cranial end of the embryo before folding.
Endocardial tubes develop within cardiogenic field.
Endocardial tubes fuse together during embryonic folding, creating the primitive heart tube.
What are the segments of the primitive heart tube?
truncus arteriosus bulbus cordis ventricle atrium sinus venosus
What is the importance of ‘looping’ and what triggers it?
As the tube elongation is confined to the pericardial space, it bends on itself. This places the atria above and behind the primitive ventricles.
Endocardial tubes develop within the cardiogenic field in week ____.
3
What does the RA develop from?
Most of primitive atrium
Part of sinus venosus
What does the LA develop from?
Part of primitive atrium
Absorbs proximal parts of pulmonary veins
Why is the RA rough lined yet the LA is smooth lined?
Primitive atrium has a rough lining, and makes up most of the RA. Whereas the pulmonary veins are smooth and make up the LA.
What is the main difference between the fetal circulation and the mature circulation?
Fetal lungs do not work
Oxygenation and CO2 removal occurs at the placenta
How is the circulatory system adapted to meet both metal and mature requirements?
Shunts in fetal circulation which are reversible at birth.
3 fetal shunts are used to by-pass which areas?
- By-pass liver after placenta
- Shunt from RA to LA (by-pass RV and lungs)
- Shunt from PT to aorta (by-pass lungs)
Why is it important that a small amount of blood enters the RV in the fetus?
Ensure normal development of the ventricle.
Shunt from pulmonary trunk to aorta to avoid lungs.
Name the 3 fetal shunts.
- Ductus venosus (by-pass liver)
- Foramen ovale (RA to LA)
- Ductus arteriosus (PT to A)
Describe how the shunts are shut at birth.
At first breath, LA pressure> RA pressure which pushes the septum premium against the septum secundum to close the foramen ovale.
Ductus artiosus contracts and closes
Placental removal causes ductus venosus to close.
How is the early arterial system arranged?
Bilateral symmetrical system of arched vessels
Which arch is remodelled to give the ‘pulmonary arch’?
6th arch gives R and L pulmonary artery