The fluid that circulates through the human cardiovascular system is known as blood. Blood is essential for transporting oxygen, nutrients, hormones, and waste products throughout the body. It consists of red blood cells, white blood cells, platelets, and plasma. Blood plays crucial roles in maintaining homeostasis, regulating body temperature, and providing immune responses. The proper functioning of the cardiovascular system is vital for overall health, as it supplies tissues with necessary substances while removing harmful byproducts from metabolism.