Medicine and Health related Information

Throughout fetal life the lungs are not functioning. Its function is taken up by the placenta. Therefore the placenta oxygenates the venous blood and also removes the waste products.
The left umblical vein carries the pure blood from the placenta to the liver of the foetus, from there it is shunted by ductus venosus into the inferior venacava. This pure blood through the I.V.C reaches the right atrium of the heart. There it is divided into two streams by crista dividens. The main stream is directed by the valve of I.V.C into the left atrium through foramen ovale from the left atrium it reaches the left ventricle. From the left ventricle through aorta it is supplied to diffrent parts of the body.
The two umblical arteries carry the impure blood from fetus to placenta for oxygenation. The superior venacava brings the impure blood to the right atrium which is directed by intervenous tubercle into the right ventricle. Then it enters the pulmonary trunk from it is shunted to the arch of aorta by ductus arteriosus.

CHANGES IN FETAL CIRCULATION AFTER BIRTH-
a) The exposure of the umblical cord to the atmosphere itself is sufficient for the closure of two umblical arteries. These are the first to close because it prevents the loss of blood from the fetus. These are converted into “lateral umblical ligaments and the 1st part of the vesicle artery”.
b) As the lungs start functioning there is increased return of blood to the left atrium. Septum primum and septum secundum comes in contact with one another. The foramen ovale is closed.
c)The lungs start functioning. Now the blood from the pulmonary trunk enters the lungs. The ductus arteriosus closes and is converted into ligamentum arteriosum.
d) In the liver the ductus venosus is converted into ligamentum venosum.
e) The left umblical vein probably the last to close because it drains the whole body from the placenta and is converted into “ligamentum teres of the liver”.