Foetal Circulation

Ekai kaoo By Ekai kaoo, 15th Aug 2013 | Follow this author | RSS Feed
Posted in Wikinut>Health>General Health>Pregnancy

This content discusses how the blood circulates in the fetus while in the uterus to the time of birth.It also states the adjustment that occur to the fetal circulation after birth.

fetal circulation in utero-life.

The foetus does not breathe in the utero. If it did, it would drown in liqour amnii. Since the foetus does not breathe, the blood does not go to the lungs for oxygen. This means that the foetus must get oxygen and nourishment through the placenta, so extra structures are required to provide for this need. Thus the foetus develops its own blood and at no time do foetal and maternal blood mixhearth

There are five temporary structures in foetal circulation.

The Umbilical Vein
This leads from the umbilical cord to the underside of the liver and carries blood rich in oxygen and nutrients. It has a branch that joins the portal vein and supplies the liver.

The Ductus Venosus
This is a vessel from the umbilical vein to the inferior vena cava, which carries oxygenated blood to the heart.

The Foramen Ovale
This is a temporary opening between the two atria in the foetal heart that allows oxygenated blood to enter the left atrium so as to be pumped out through the aorta.

The Ductus Arteriosus
This vessel connects the pulmonary artery to the descending arch of aorta. It deoxygenates blood from the head and upper limbs thereby
bypassing the pulmonary circulation.

The Hypogastric Arteries
These two vessels branch off from the internal iliac arteries. They are known as umbilical arteries when they enter the umbilical cord.
All foetal blood passes through the placenta to get oxygen and nutrients and to eliminate waste. The course taken by the blood through the foetal circulation is as shown opposite.
The blood takes about half a minute to circulate. Oxygenated blood (50% saturated with oxygen) and nutrients flow through the placenta to the umbilical vein.
The umbilical vein takes the purified blood from the placenta and enters the baby's body at the umbilicus, then runs beneath the anterior abdominal wall to the under-surface of the liver (the liver gets the most oxygenated blood in the foetus). Here it gives off two branches to the left lobe. A small branch is also given off to join the portal vein and takes blood to the right lobe.

The vein now becomes the ductus Venosus and carries the blood to the inferior vena cava where it mixes with blood from the lower parts of the body. The blood then enters the right atrium and most of it passes through the foramen Ovale into the left atrium. In this way, it bypasses the lungs.
The blood then passes through the mitral valve into the left ventricle and out through the aorta. The aorta gives out branches to the head, neck and arms. These, therefore, receive purer blood than any part of the foetal body except the liver.

Deoxygenated blood from the head, neck and arms passes through the superior vena cava to the right auricle and is directed through the tricuspid valve to the right ventricle. From the right ventricle the blood enters the pulmonary artery. A small branch takes a small amount of blood to the functionless lungs. The remaining blood passes through the ductus Arteriosus to the aorta to supply the remaining body organs and legs.
The internal iliac arteries lead into the hypo gastric arteries, which return blood to the placenta via the umbilical arteries. The external iliac artery supplies blood to the lower extremities and returns to the inferior vena cava.
The umbilical arteries then pass into the abdominal wall to the umbilical cord at the navel and so reach the placenta where the blood passes through the chronic villi for respiratory and metabolic exchange, ready to circulate through the foetus again.


Blood, Heart, Umbilical Cord

Meet the author

author avatar Ekai kaoo
Am a fourth year student undertaking Bachelor of science in Nursing.I like writing articles of medical field.

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