Venae Cavae

the main venous trunks of the systemic circulatory system in land vertebrates. By way of the venae cavae, blood is pumped into the venous sinus of the heart of amphibians and directly into the right auricle of amniotes.

Each of the paired anterior venae cavae (absent in caudate amphibians) is formed by a mergence of the anterior cardinal veins with the exterior jugular subclavian veins, with the ducts of Cuvier constituting the terminal section. The anterior vena cava in some mammals (the superior vena cava in man) is secondarily unpaired and preserved only on the right. The superior vena cava collects blood from the head, neck, thoracic walls, upper extremities, and partially from the abdominal walls.

The unpaired posterior vena cave, which first developed in bichirs and lungfish, is characteristic of land vertebrates. The anterior section of the posterior vena cava developed from hepatic veins that proliferated posteriorly. Behind this section is a segment composed of the kidney’s efferent veins. Owing to the absence of a kidney portal system, the posterior vena cava in mammals (the inferior vena cava in man) includes a section formed by a mergence of common iliac veins behind the kidneys. The inferior vena cava collects blood from the lower extremities, the walls and organs of the abdominal cavity, the pelvic organs, and the spinal cord.