How blood is circulated inside the foetus?
Inside the womb, a developing foetus receives oxygen and nutrients from its mother through the placenta, which is connected to the foetus by the umbilical cord. The blood circulation in the foetus differs from that of a newborn baby or an adult. Here's how blood circulation occurs inside the foetus:
1. Umbilical Cord: The umbilical cord consists of three blood vessels: one umbilical vein and two umbilical arteries.
2. Oxygenated Blood: Oxygen-rich blood from the placenta enters the foetus through the umbilical vein. This blood carries oxygen and nutrients essential for the foetus's growth and development.
3. Ductus Venosus: The umbilical vein leads to the ductus venosus, a specialised blood vessel that bypasses the liver and directs most of the oxygenated blood directly to the inferior vena cava (IVC).
4. Foramen Ovale: The inferior vena cava carries the oxygenated blood to the right atrium of the foetal heart. A specialised opening called the foramen ovale allows most of this oxygenated blood to flow directly into the left atrium, bypassing the foetal lungs which are not yet functional.
5. Left Ventricle and Aorta: From the left atrium, the oxygenated blood flows into the left ventricle and is pumped out into the systemic circulation. The aorta carries this oxygenated blood to various parts of the foetus's body, delivering oxygen and nutrients to the tissues.
6. Deoxygenated Blood: Deoxygenated blood from the foetus's body is returned to the placenta via the umbilical arteries. These arteries carry waste products, including carbon dioxide, back to the placenta.
7. Placental Exchange: Within the placenta, the deoxygenated blood from the foetus comes into close proximity with the oxygenated maternal blood, allowing for the exchange of gases and nutrients. Oxygen and nutrients from the mother diffuse into the foetal bloodstream, while carbon dioxide and waste products move from the foetus to the maternal circulation.
This unique circulatory system ensures that the foetus receives a constant supply of oxygen and nutrients while eliminating waste products. After birth, the circulatory system undergoes changes as the baby begins breathing on its own, leading to the closure of the foramen ovale and ductus venosus, and the establishment of the adult-like circulatory pattern.