Family medicine is a sub-field of medicine that is focused on the health of the whole family, from infancy to advanced age. Family medicine doctors care for patients of all ages, from newborns to the elderly, and also specialize in treating diseases and conditions that primarily affect families, such as heart disease, diabetes, and asthma. With their broad range of knowledge, family medicine doctors can diagnose, treat and prevent injuries and illnesses that affect any part of the body or the body systems as a whole, such as the skin, the nervous system, the joints, the bones, and the heart. Family medicine doctors are often the first healthcare providers patients see when they are sick or injured, acting as the gateway to the healthcare system.