The document discusses several factors that affect the healthy function of the body's main systems. It focuses on three systems: respiratory, circulatory, and digestive. For the respiratory system, diseases like asthma can affect the lungs. Smoking is a major social factor that increases risk of respiratory diseases due to chemicals in cigarettes like tar and carbon monoxide. The circulatory system is impacted by diet and high cholesterol leading to conditions like atherosclerosis and heart attacks. Factors like diet, bacteria, and ulcers can influence the digestive system and cause issues like stomach pains and indigestion.