FETAL BLOOD CIRCULATION
- Placenta - Organ of gas exchange
Pattern of blood flow:
Placenta → highly oxygenated blood → Umbilical vein (arises from internal iliac vein) → divides into left, right umbilical veins.
Left umbilical vein → Portal vein → liver → hepatic vein → IVC (contains deoxygenated blood from lower limbs) → Right atrium. (only if the pressure of blood ↑↑)
Right umbilical vein → ductus venosus (bypass liver) → IVC → mixed blood (high O₂ conc.) ↑ → right atrium.
Right atrium via foramen ovale → left atrium
↑ Small amount of blood from right atrium enters right ventricle → Pulmonary art. → lungs.
left atrium → left ventricle → Aorta ← via ductus arteriosus → because of pressure
Aorta → Systemic circulation (R.L. common iliac arteries) → Umbilical arteries 2 → Placenta.
Remnant structures after birth:
- 1 Ductus Arteriosus: After birth closes becoming the ligamentum arteriosum 9~12-24 hours.
- 2. Foramen Ovale: " " " forming the fossa ovalis in the right atrium of adult heart.
- 3. Ductus venosus: " " " ligamentum venosum of the liver.
- 4. Umbilical Arteries & veins: " " arteries → medial umbilical ligament; vein → Round ligament of the liver.
mixed blood: the organs use the oxygenated blood & pass the deoxygenated blood.