Pathology. Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek ÏÎ¬Î¸Î¿Ï, pathos which may be translated into English as either experience or suffering. and -Î»Î¿Î³Î¯Î±, -logia, An account of or the study of.
Red cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin.
Human blood is red because it contains a large number of red blood cells, which contain hemoglobin. Hemoglobin is a red-colored, iron-containing protein that functions in oxygen transport by reversibly binding to oxygen. Oxygenated hemoglobin and blood are bright red; deoxygenated hemoglobin and blood are dark red. Human blood does not appear blue under any circumstances. In fact, vertebrate blood in general is red. An exception is skink blood, which appears green because it contains a large amount of the protein biliverdin.