Fetal Circulation and Birth Changes

The umbilical vein, a part of the fetal circulation, shrinks and becomes a ligament in the liver after birth.

The ductus venosus, a fetal blood vessel that connects the umbilical vein to the inferior vena cava, turns into a ligament after birth.

The foramen ovale, an opening in the heart that allows blood to bypass the lungs in the fetus, closes after birth, leaving a depression called fossa ovalis.

The ductus arteriosus, a blood vessel that connects the pulmonary artery to the aorta in the fetus, shrinks after birth and becomes a fibrous ligament.

The umbilical arteries, which carry deoxygenated blood from the fetus to the placenta, shrink and become ligaments after birth.

The umbilical vein carries oxygenated blood from the placenta to the fetus.

The ductus venosus connects the umbilical vein to the inferior vena cava, bypassing the liver.

The foramen ovale is a small opening that allows blood to bypass the lungs by flowing from the right atrium to the left atrium.

The ductus arteriosus is a blood vessel connecting the pulmonary artery to the aorta, allowing blood to bypass the lungs.

The two umbilical arteries carry de-oxygenated blood and fetal waste from the fetus back to the placenta.

The placenta is a vital organ that provides oxygen and nutrients to the fetus and removes waste products.

Fetal circulation is a complex system of blood vessels and structures that allow the fetus to receive oxygen and nutrients while its organs are still developing.

The transition from fetal to infant circulation involves the closure of the ductus venosus, foramen ovale, and ductus arteriosus. This allows the heart and lungs to function independently.

The umbilical arteries carry deoxygenated blood from the fetus to the placenta.

The placenta is the organ that provides oxygen and nutrients to the fetus and removes waste products.

Fetal Circulation is a low-pressure system due to the underdeveloped lungs not functioning as a primary oxygen source.

The clamping of the umbilical cord at birth shuts down the low-pressure fetal circulation system.

With the lungs inflating with oxygen, the pulmonary vessels open up, increasing blood flow and lowering pressure.

As the pressure in the left atrium increases, the foramen ovale closes due to the pressure difference between the left and right atria.

The pulmonary arteries carry oxygenated blood from the heart to the lungs.

The closure of the foramen ovale is a critical physiological change that occurs shortly after birth, as the baby transitions from fetal to infant circulation. It's triggered by the increased pressure on the left side of the heart due to the increased blood flow from the lungs. This forces the flap of tissue in the foramen ovale to close, preventing further blood flow from the right atrium to the left atrium.

The ductus arteriosus, a temporary vessel connecting the pulmonary artery to the aorta, constricts after birth. This is due to the increased oxygen levels in the blood, the release of bradykinin, and a reduction in prostaglandins. As a result, blood flow through the ductus arteriosus decreases, leading to its functional closure.

A 'patent ductus arteriosus' occurs when the ductus arteriosus fails to close after birth. This can cause problems with blood oxygen levels and lead to heart complications. In this condition, blood continues to flow from the aorta to the pulmonary artery, resulting in a decrease in the oxygen saturation of aortic blood.

The ductus venosus, a fetal vessel that connects the umbilical vein to the inferior vena cava, closes after birth. This is due to the increased pressure in the portal vein, which results from the liver starting to function fully. This closure prevents blood from bypassing the liver and ensures proper blood processing and detoxification.

A 'portosystemic shunt' occurs when the ductus venosus fails to close after birth. This leads to blood bypassing the liver, potentially causing a range of problems, including liver dysfunction and developmental issues.

Loss of placental circulation after birth triggers several significant changes in the baby's circulatory system. One key change is an increase in systemic vascular resistance, which is the resistance to blood flow in the systemic circulation. This increase in resistance is due to the loss of the low-resistance placental circulation.

The change from right to left shunting to left to right blood flow is a crucial physiological transition that takes place after birth. In the fetus, blood flows from the right atrium to the left atrium through the foramen ovale, bypassing the lungs. However, after birth, with the lungs fully functional and the foramen ovale closed, blood flow shifts to a left-to-right pattern, with the left side of the heart pumping oxygenated blood throughout the body.

The pressure in the right atrium decreases after birth, primarily due to the lowered resistance in the pulmonary arteries. This occurs because the lungs are now fully functional, requiring less pressure to push blood through them. This decrease in pressure helps drive the shift from right to left shunting to left to right blood flow.