Cardiopulmonary Resuscitation
LESSON 1: REVIEW OF THE CIRCULATORY AND RESPIRATORY SYSTEMS
1-2
1-2. IMPORTANCE OF THE CIRCULATORY SYSTEM
The human body is composed of cells. The average adult human's body is made up of around eighty trillion (80,000,000,000,000) living cells. Cells need energy to survive, repair themselves, perform their functions, and reproduce. Cells obtain this energy through cellular respiration; that is, they combine a source of potential energy with oxygen to liberate energy. The sources of potential energy come from the food (carbohydrates, fats, and proteins) that are processed into usable units by the body's digestive system (stomach, small intestine, liver, pancreas, and so forth). The oxygen comes from the air that is inhaled by the lungs. Oxygen in the lungs and food in the intestine cannot help the muscles and other cells unless the oxygen and food can be delivered to those cells. Delivering oxygen and food to the cells is the function of the blood in the body's circulatory system. The circulatory system also takes waste products (by-products of cellular respiration) from the cells and delivers them to organs (lungs and kidneys) where the wastes can be expelled from the body.
