156 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. Fractures A fracture is a break or crack in a bone. The nature of a fracture depends on the size, direction, and duration of the injurious force, as well as the health and maturity of the bone. Fractures are classified as simple when the bone ends remain within the surrounding soft tissues, and compound when one or both bone ends protrude from the skin. When the bone is splintered, the fracture is said to be comminuted. See Figure 5.36. C onsidering all of the important functions performed by bone, bone health is a vital part of general health. Bone health can be diminished by injuries and pathologies. Common Bone Injuries Perhaps the most common, and often the most visible, types of bone injuries are fractures of various types. However, other types of injuries, such as epiphyseal injuries, are also possible. hinge joint a type of diarthrosis that allows only hinge-like movements in forward and backward directions ligament a band of collagen and elastic fibers that connects bones to other bones pivot joint a type of diarthrosis that permits rotation around only one axis saddle joint a type of diarthrosis in which the articulating bone surfaces are both shaped like the seat of a riding saddle symphysis a type of amphiarthrosis in which a thin plate of hyaline cartilage separates a disc of fibrocartilage from the bones synarthrosis a fibrous joint that can absorb shock, but which permits little or no movement of the articulating bones synchondrosis a type of amphiarthrosis joint in which the articulating bones are held together by a thin layer of hyaline cartilage syndesmosis a type of synarthrosis joint at which dense, fibrous tissue binds the bones together, permitting extremely limited movement synovial joint a diarthrodial joint tendon a band of collagen and elastic fibers that connects a muscle to a bone tendon sheaths double-layered synovial structures surrounding tendons that are subject to friction because they are located so close to bones secrete synovial fluid to promote free motion of the tendons during joint movement Review Questions 1. What does it mean to say that bones articulate with each other? 2. Give two examples of immovable joints and state where they are found in the body. 3. Give two examples of slightly movable joints and state where they are found in the body. 4. Give six examples of freely movable joints and state where they are found in the body. 5. Why is it important to have a layer of cartilage between bones that articulate with each other? 6. Why does the human body need joints that permit little to no movement in the skeleton? 7. What happens when articular cartilage begins to erode from excessive wear and stress on a joint? SECTION 5.6 Injuries and Disorders of the Skeletal System Objectives • Identify the different types of bone and epiphyseal injuries, and explain the forces that can cause each of these injuries. • Discuss osteoporosis, including contributing factors, groups at risk, consequences, and prevention strategies. • Describe the common types of joint injuries, including the structures affected, symptoms, and common treatments. • Explain what is involved with arthritis and describe specific types of arthritis. Key Terms amenorrhea anorexia nervosa apophysis arthritis bulimia nervosa bursitis dislocation female athlete triad fracture osteoarthritis osteopenia osteoporosis rheumatoid arthritis sprain