Fetal circulation Flashcards
What are the unique features of fetal circulation ?
The presence of the placenta ( 1 umbilical vein & 2 umbilical arteries) The shunts : Ductus venosus Foramen ovale Ductus arteriosus
Where does the highest O2 saturation in the fetus is?
1- In the umbilical vein of the placenta , it reaches the maxmium O2 saturation in a fetus which accounts for 80%
Explain the route of oxygenated blood in a fetus
Umbilical vein (80% O2 saturation)>The liver (not fully functioning so only a small amount of blood would pass through the hepatic portal vein)>First shunt ( Ductus Venosus )>Mixing of the blood with the IVC ( O2 saturation reaches 65%)>Right atrium > 2nd shunt , foramen ovale > Left atrium>Left ventricle >Ascending Aorta> Vessels of the head, neck, and arm.
What is a Ductus venosus , where is it located ? and name the remnant post-nataly?
The first shunt , located in the liver , it connects the umbilical vein to the IVC, it carries oxygenated blood and it remains after birth as ligamentum venosum.
What is the foramen ovale , where is it located ? and name the remnant post-nataly?
An opening in the interatrial septum and it’s the second bypass pathway, it bypasses the non ventilated lungs , Oxygenated blood moves from the RA to the LA, remnant is fossa ovalis
What is the Ductus arteriosus , where is it located ? and name the remnant post-nataly?
Third bypass , it connects the pulmonary trunk to the aorta and carries deoxygenated blood from the SVC to the RA>RV>pulmonary trunk >descending aorta>internal iliac artery>umbilical arteries
when does cyanosis appears visible ?
if the deoxygenated hemoglobin is more than 3g per 100ml
Define central cyanosis
If the cyanosis is found is within the tongue or mucus membranes.
Define peripheral cyanosis
cyanosis that is limited to the extremities, can also be called acrocyanosis , due to exposure to cold or polycythemia.
what can cause a persistent fetal circulation ?
hypoxia , hypercarbia , acidosis and cold = increased pulmonary vasoconstriction and increased pulmonary vascular resistance= right to left shunting of the blood
what will the umbilical arteries remain as ?
the proximal part will remain as the superior vesical artery that will supply the superior bladder and the distal part will remain as the medial umbilical ligament.
Describe how will the ductus arteriosus close after birth ?
increased pressure in the left side of the heart and decreased resistance / pressure in the pulmonary arteries leading to :
1-Release of bradykinin from the lungs that will act as a vasoconstrictor.
2- Decreased amounts of prostaglandin E2(vasodilator)
3- increased oxygen tension
