Fluid that, in all vertebrates, carries the oxygen (bound to the haemoglobin in the red blood cells) from the lungs to the tissues and returns the carbon dioxide. It also distributes soluble products of digestion to modifying organs, such as liver, and to the tissues, which return waste products that are transported to the kidneys. In the blood antibodies and the white blood cells take care of infections of invading organisms such as viruses and bacteria. Hormones (special proteins) are transported from glands and regulate the actions and activity of the various organs. Last but not least the blood acts as a kind of "central heating system" by distributing warmth through the body and keeps the body environment constant.

Alternative form for blood : blooded.