Blood platelet abstract CGI. Blood is a specialized bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen and transports waste products away from those same cells. Capillaries are the smallest of a body's blood vessels and are part of the microcirculation. Monocytes(shown here as in white) eventually leave the bloodstream to become tissue macrophages which remove dead cell debris as well as attack micro organisms. Free stock videos from animation company Polymime.