not a doc, but did some searching / reading after i read this, so correct me if i'm wrong.

it flows around in the plasma. Plasma is the liquid portion of the blood. Blood cells like red blood cells float in the plasma. Also dissolved in plasma are electrolytes, nutrients and vitamins (absorbed from the intestines or produced by the body), hormones, clotting factors, and proteins such as albumin and immunoglobulins (antibodies to fight infection). Plasma distributes the substances it contains as it circulates throughout the body

(** last portion copied from a web-site www.howstuffworks.com)