[fig51.bmp]

Fig. 5.1 Fetal circulation.

Key: 1. Oxygenated blood from the placenta flows through the caudal vena cava and enters the right atrium, where it is funnelled through the foramen ovale into the left atrium. 2. Deoxygenated blood returning from the cranial vena cava is guided through the right atrium into the right ventricle. 3. Richly oxygenated blood is delivered to the heart and brain. 4. Blood from the pulmonary artery is diverted through the ductus arteriosus into the aorta, bypassing the high pressure pulmonary circuit and supplying the low pressure systemic circulation (except the heart and brain l. 5. A large portion of aortic blood flow is directed towards the placenta through the umbilical artery. 6. Some blood from the systemic circulation passes through the liver.7. Some placental blood supplies the liver but a large proportion of. this richly oxygenated blood passes through the venosus into the caudal vena cava.