The fluid consisting of plasma, red blood cells, white blood cells, and platelets that is circulated by the heart through the arteries and veins, carrying oxygen and nutrients to and waste materials away from all body tissues.
One of the four humors of ancient and medieval physiology, identified with the blood found in the blood vessels, and believed to cause cheerfulness.
descent from a common ancestor; parental lineage.
|blood (blŭd) Pronunciation Key
The fluid circulating through the heart, arteries, veins, and capillaries of the circulatory system. Blood carries oxygen and nutrients to the cells of the body and removes waste materials and carbon dioxide. It is composed of plasma (mainly water, but with a mixture of hormones, nutrients, gases, antibodies, and wastes), red blood cells (which carry oxygen), white blood cells (which help combat infection), and platelets (which help the blood clot).