- Bile duct - primordial duct links primitive intestine and liver parenchyma. Thick-walled tube (95 µm diameter) small lumen (22 µm diameter).
- Gall bladder - elongated tube further dilated, thick wall (125 µm diameter) and a narrow lumen (43 µm diameter).
- Hepatic sinusoids - intra-hepatic vasculature present
- Three venous tributaries flow into the liver sinusoids - right and left placental vein and a single vitelline vein.
- Cords of liver cells fragmented by vascular network of hepatic sinusoids.
- Between pericardial cavity (top) and mesonephros (bottom).
- Upper pole of the liver lies close to the septum transversum and early ventricles.
- Liver occupies the majority of abdominal cavity.
- Bile duct (future common bile duct), and a common hepatic duct, in contact with liver parenchyma without penetration.
- Primordium of accessory bile tract is an elongated and fusiform gall bladder projecting forward and by a short cystic duct that opens into common bile duct.
- Bile duct empties into second part of duodenum on its posterior side.
- Portal system visible - portal vein (100 µm diameter) arises from connection of upper mesenteric vein then at region of hepatic hilum (285 µm) divides into portal branches.
- Left umbilical vein empties into anterior extremity of the left portal branch.
- Ductus venosus (80 µm) connects the initial portion of left portal vein to the inferior vena cava.
- Hepatic venous system 3 branches - left hepatic vein (120 µm in diameter), middle hepatic vein (220 µm in diameter) and right hepatic vein (160 µm in diameter). Flows into the sub-cardinal vein.
- Liver parenchyma has two anatomical lobes (right and left lobe), separated by anteroposterior plane formed by placental vein.
||Bile duct morphology as earlier stage. Common bile duct empties at the level of the proximal duodenum.
- Portal vein arises from joining of splenic vein and superior mesenteric vein. At the level of the hepatic hilum, portal vein divides into two branches, right portal branch (420 µm in diameter) and left portal branch (540 µm in diameter). Right portal branch gives rise to a thin branch to caudate lobe. Ventral branch gives rise to segmental portal veins (VIII and V). Dorsal branch gives rise to the segmental portal veins (VI and VII).
- Ductus venosus connects initial portion of left portal vein to inferior vena cava, just upstream from hepatic vein afferents.
- Hepatic venous system as for previous stage.
|Hepatic parenchyma a large rounded mass.
||Bile duct morphology as earlier stage.
- Portal venous system complete.
- Ductus venosus (40 µm) connects initial portion of portal vein to middle hepatic vein.
- hepatic venous system has changed very little from the previous stage. Three hepatic veins empty into inferior vena cava.
- Liver parenchyma roughly oval shape, 2 symmetrical hepatic lobes. The quadrate and caudate lobes are identifiable.
- Upper pole of the liver bounded above by diaphragm.
|Data from a recent human study|
Links: liver | Carnegie stage 14 | 18 | 21 | 23 | simple embryonic timeline | Timeline human development