Foetal circulation (1)
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The fetal circulation allows oxygenated blood from the placenta to bypass the lungs and circulate throughout the fetus's body. Key structures include the umbilical vein, which carries oxygenated blood from the placenta to the liver, the foramen ovale and ductus arteriosus which allow blood to bypass the lungs, and the umbilical arteries which return deoxygenated blood to the placenta. The circulatory process involves blood passing from the placenta through the umbilical vein, mixing with deoxygenated blood and passing through the foramen ovale and ductus arteriosus to supply the fetus before returning to the placenta through the umbilical arteries.
Foetal circulation (1)
- 1. FETAL CIRCULATION Presented by: A.Priyadharshini M.Sc(N), Lecturer, Jai institute of nursing and research, Gwalior.
- 2. INTRODUCTION: • The key to understand the fetal circulation is the fact that oxygen is derived from the placenta! • In addition the placenta is the source of nutrition and the site of elimination of waste.
- 3. Temporary structures in fetal period: Umbilical vein Umbilical arteries Ductus venosus Foramen ovale Ductus arteriosus
- 4. Umbilical vein: This vein leads from the umbilical cord to the underside of the liver and carries blood rich in oxygen and nutrients. It has a branch and joins the portal vein and supplies the liver.
- 5. The ductus venosus: (from a vein to vein) This connects the umbilical vein to the inferior venacava. At this point the blood mixes with the deoxygenated blood returning from the lower parts of the body. Thus the blood throughout the body is at best partially oxygenated.
- 6. The foramen ovale: ( oval opening) This is a temporary opening between the atria that allows the majority of blood entering from the inferior venacava to pass across into the left atrium. The reason for this diversion is that the blood does not need to pass through the lungs to collect oxygen.
- 7. The ductus arteriosus ( from artery to artery) This leads from the bifurcation of the pulmonary artery to the descending aorta, entering it just beyond the joint point where the subclavian and carotid arteries leave.
- 8. Umbilical arteries: These branch off from the internal iliac arteries and become the umbilical arteries when they enter the umbilical cord. They return blood to the placenta.
- 9. The circulatory process: • The blood takes about half a minute to circulate. • From the placenta, blood passes along the umbilical vein through the abdominal wall to the under surface of the liver. This is the only vessel in the fetus that carries unmixed blood.
- 10. • The ductus venosus carries blood to the inferior venacava where it mixes with the blood from the lower body. • From here the blood passes into the right atrium and most of it is directed across through the foramen ovale into the left atrium. • Following its normal route it enters into the left ventricle and passes into the aorta.
- 11. • The heart and brain receives a supply of relatively high oxygenated blood since the coronary and carotid arteries are earlier branches of aorta. • The arms also benefit via the subclavian arteries. Arms are well developed for this reason.
- 12. • Blood collected from the upper parts of the body returns to the right atrium in the superior venacavaa. This blood is depleted of oxygen and nutrients. • This stream of blood crosses the stream entering from the inferior venacava and passes into the right ventricle.
- 13. • The two streams remain separate because of the shape of the atrium but there is a mixing of 25% of the blood, allowing a little oxygen and nutrients to be taken into the lungs through the pulmonary artery. This is necessary for the lung development.
- 14. • The remainder blood passes through the ductus arteriosus to the aorta. Blood continues along the aorta and although low in oxygen, has sufficient to supply the remaining organs and legs. • The internal iliac arteries lead into the hypogastric arteries, which return blood to the placenta via the umbilical arteries.
- 15. • The remaining blood supplies the lower limbs and returns to the inferior venacava.
- 16. Flow Chart of Fetal Circulation