foramen ovale is located where on the fetal heart
Foramen ovale (heart) The foramen ovale (from Latin, meaning 'oval hole') forms in the late fourth week of gestation, as a small passageway between the septum secundum the ostium secundum. Initially the atria are separated from one another by the septum primum except for a small opening below the septum, the ostium primum. As the septum primum grows, the ostium primum narrows and eventually closes. Before it does so, bloodflow from the inferior vena cava wears down a portion of the septum primum, forming the ostium secundum. Some embryologists postulate that the ostium secundum may be formed through programmed cell death.[4]
Small intestine Food from the stomach is allowed into the duodenum through the pylorus by a muscle called the pyloric sphincter.
Fetal circulation Blood from the placenta is carried to the fetus by the umbilical vein. In humans, less than a third of this enters the fetal ductus venosus and is carried to the inferior vena cava,[2] while the rest enters the liver proper from the inferior border of the liver. The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein. The blood then moves to the right atrium of the heart. In the fetus, there is an opening between the right and left atrium (the foramen ovale), and most of the blood flows through this hole directly into the left atrium from the right atrium, thus bypassing pulmonary circulation. The continuation of this blood flow is into the left ventricle, and from there it is pumped through the aorta into the body. Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation.[1]
Pulmonary circulation From the right ventricle, blood is pumped through the semilunar pulmonary valve into the left and right main pulmonary arteries (one for each lung), which branch into smaller pulmonary arteries that spread throughout the lungs.