The sixth aortic arch becomes the pulmonary arteries, which are derived from a common pulmonary trunk on the aorta. The dorsal aorta is the large median longitudinal artery that extends posteriorly and eventually branches into the caudal artery. Subintestinal-vitelline system Drains the tail, digestive tract and yolk sac. Also includes the caudal vein, which runs to the cloacal area. Cardinal system Drains the head, dorsal body wall and kidneys.
Abdominal system Drains the ventral body wall and appendages.
Consists of the lateral abdominal veins, which receive blood from the iliac and subclavian veins. The anterior veins are derived from the cardinal system. The hepatic portal system is derived from the subintestinal system. The hepatic portal vein receives blood from the gut region. Inside the liver the vein breaks up into hepatic sinusoids, where the blood comes into contact with hepatic cells and phagocytic cells.