Physiological changes occur with aging that affect nearly every system of the body. The skin shows signs of aging like wrinkling due to loss of fat and muscle beneath. Joints are affected by conditions like osteoarthritis. Muscle mass declines along with bone density. The heart and blood vessels become stiffer. Lung function decreases. Urinary control weakens. Hormone levels change with menopause and declining testosterone. While aging processes are universal, the rate varies between individuals.