Chapter 6: aging of the internal organ systems. The cardiovascular system is the body"s main transportation system. It sends supplies such as fluids, nutrients, hormones, oxygen, and antibodies to tissues in the body while at the same time removing waste products such as carbon dioxide and hydrogen ions. The system is composed of the heart, blood vessels (arteries, arterioles, capillaries, veins and venules), and blood. In general, arteries carry blood away from the heart, and veins carry blood to the heart. Blood is a highly complex fluid composed of water, red and while blood cells, and platelets, as well as nutrients such as fat globules, carbohydrates, and proteins. It is perfused by gases such as oxygen, carbon dioxide, and nitrogen. Blood also carries electrolytes, to help maintain the acid/base balance, and a host of other chemicals, including hormones, neurotransmitters, and various other peptides necessary to regulate homeostasis, cognition, movement, and every other function of the body.