1 - Cardiovascular Embryology Flashcards
What does the umbilical vein do?
Carry oxygenated blood towards the fetus
What does the umbilical artery do?
Carry de-oxygenated blood back towards maternal circulation
What are the 3 important shunts exist in fetal circulation?
What is there overall function?
Ductus venosus
Foramen ovale
Ductus arteriosus
Increase oxygenation to the BRAIN.
What two vessels form the ductus venosus?
Left umbilical vein
Left branch of the hepatic portal vein
Where does the ductus venosus drain from, into?
Umbilical vein
Inferior vena cava
What are the 2 functions of the ductus venosus?
Shunts oxygenated blood past the sinusoids of the liver (already been cleansed by mother?)
Act as a mechanism to reduce right atrium venous return (in case of it being excessive)
What structure does the ductus venosus become after birth?
Ligamentum venosum (ligament continuous with the round ligament of the liver)
The left umbilical vein becomes what structure after birth?
Ligamentum teres
What % is shunted through the liver?
What controls it?
Why is this significant?
20-30%
Sphincter
Relatively small proportion in comparison to other animal species, which suggest underestimation in the function of the fetal liver.
How soon after birth does ductus venosus closure occur?
Functionally - minutes
Structurally - days/week
**Blood coagulates within the structure and becomes fibrosed with time.
What is the function of the foramen ovale?
Shunts oxygenated blood from the right to the left atrium.
What structure does it become following birth?
Fossa ovale / ovalis
What occurs following incomplete closure of the foramen ovale?
Patent foramen ovale
most common atrial septal defect
What clinical consequence occurs if this is the case?
Cyanosis (bluish tinge to skin / mucous membranes)
Where does the ductus arteriosus shunt blood from and to?
Shunt blood from pulmonary trunk to aorta
What are the functions of the ductus arteriosus?
1) Reduce pulmonary circulatory load (protect the lungs)
2) Enables right ventricle to strengthen
What does the ductus arteriosus become following birth?
What is its function?
Ligamentum arteriosum
Acts as a tether to hold the aorta and pulmonary trunk together
What feature of the lungs favours the blood’s passage to occur through the ductus arteriosus?
High pulmonary vascular resistance
Occlusion of the fetal circulation results in a drop in BP in which two connected areas?
IVC
Right atrium
What stimulates vasoconstriction of both ductus arteriosus / venosus?
Increasing oxygen content from first and subsequent breaths.
Aeration of the lungs is associated with 3 consequential changes?
1) Lung expansion reduces pulmonary resistance
2) Pulmonary blood flow increases
3) Left atrium pressure > IVC / right atrial pressure
Control of circulation is regulated by which two sets of receptors?
Peripheral baroreceptors (carotid sinus / aortic arch)
Central baroreceptors in cardiovascular centre of medulla
Through what mechanism does the foramen ovale close?
Before birth, RA pressure > LA pressure.
When born, venous return from placenta / IVC decreases, stops holding foramen ovale open.
Oxygenated blood return form pulmonary circulation stops passage of blood across shunt (due to pressure) because septum primum closes against relatively rigid septum secundum.
What ventricular changes also arise following birth?
In utero, right ventricle is stronger / thicker than left. Following shunt closure, the pressure in the left ventricle increases which encourages it to get stronger + RV demand is lower so lessens.
