Circulatory system of the horse capacity of the muscular system far exceeds the capacity of the cardiovascular system to deliver oxygen. Blood is made up of red blood cells (erythrocytes) and white blood cells (leukocytes), as well as plasma. Produced in bone marrow, red blood cells are responsible for carrying oxygen to tissue and removing carbon dioxide, all via hemoglobin. White blood cells are used for defense against pathogens in the immune system. Plasma suspends the blood cells, contains clotting factors, and contributes to the greatest volume of blood. The heart and blood vessels contain approximately of blood in a horse, which equates to about
Packed red blood cells they can be frozen for up to 10 years. The cells are separated from the fluid portion of the blood after it is collected from a donor, or during the collection process in the case of apheresis. The product is then sometimes modified after collection to meet specific patient requirements. The product is typically abbreviated RBC, pRBC, PRBC, and sometimes StRBC or even LRBC (the latter being to indicate those that have been leukoreduced, which is now true for the vast majority of RBC units). The name "Red Blood Cells" with initial capitals indicates a standardized blood product in the