Hepatic sinusoids (portal and umbilical mixing)
Venous return · SaO2 ~70-80%
The larger share of umbilical venous blood perfuses the liver: the left lobe almost purely from the umbilical vein, the right lobe after mixing with poorly oxygenated portal blood from the gut. Hepatic venous blood then re-enters the IVC just below the heart.
Traced from the start
- Placenta
- Umbilical vein
- Hepatic sinusoids (portal and umbilical mixing)
Detail
- Share
- Roughly 70-80% of umbilical venous flow at term (the part not shunted through the ductus venosus) passes through the liver
- Saturation
- ~80% entering the left lobe; lower in the right lobe after admixture with portal venous blood from the gut
- Drainage
- Left hepatic vein joins the ductus venosus stream toward the foramen ovale; right hepatic vein joins the abdominal IVC stream toward the right ventricle
- Fetal liver
- Site of glycogen storage and second-trimester haematopoiesis; its perfusion is sacrificed first when oxygen is short
When it goes wrong
Chronic fetal hypoxaemia (placental insufficiency)
Blood is diverted from liver to ductus venosus, so hepatic growth and glycogen fall behind: abdominal circumference lags head circumference on ultrasound (asymmetric growth restriction) and neonatal hypoglycaemia follows
Practise this structure
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