Blood

Blood is a highly specialized circulating tissue consisting of several types of cells suspended in a fluid medium known as plasma. The cellular constituents are: red blood cells, which carry respiratory gases and give it its red color because they contain hemoglobin (an iron containing protein that binds oxygen in the lungs and transports it to tissues in the body), white blood cells (leukocytes), which fight disease, and platelets, cell fragments which play an important part in the clotting of the blood. Medical terms related to blood often begin with hemo- or hemato- (BE: haemo- and haemato-) from the Greek word "haima" for "blood." Anatomically, blood is considered a connective tissue from both its origin in the bones and its function.