The part of the cardiovascular system consisting of all venous vessels. In vertebrates with a double circulation, this can be divided into systemic and pulmonary portions.

vein system

uberon

The appearance of Chordata and subsequently the vertebrates is accompanied by a rapid structural diversification of this primitive linear heart: looping, unidirectional circulation, an enclosed vasculature, and the conduction system.[well established][VHOG]

UBERON:0004582

http://purl.obolibrary.org/obo/uberon.owl, http://purl.obolibrary.org/obo/cl.owl

• venous blood vessel