Individual capillaries are part of the capillary bed, an interweaving network of capillaries supplying tissues and organs. In the mesentery, metarterioles form an additional stage between arterioles and capillaries. The capillaries then join and widen to become venules, which in turn widen and converge to become veins, which then return blood back to the heart through the venae cavae.

Blood flows from the heart through arteries, which branch and narrow into arterioles, and then branch further into capillaries where nutrients and wastes are exchanged.