Chapter 4 The Skeletal System 153 Tendons, which connect muscles to bones, and ligaments, which connect bones to other bones, are also present at the diarthrodial joints. Composed of collagen and elastic fibers, these tissues are slightly elastic and will return to their original length after being stretched, unless overstretched to the point of injury. The tendons and ligaments crossing a joint play an important role in joint stability. The hip joints, in particular, are crossed by a number of large, strong tendons and ligaments. Check Your Understanding 1. What is the purpose of articular fibrocartilage? 2. In functional terms, what is the difference between a tendon and a ligament? Articular Tissues The joints of any mechanical device must be properly lubricated if the movable parts are to move freely and not wear against each other. In the human body, articular cartilage covers the ends of bones at diarthrodial joints and provides a protective lubrication. Articular cartilage cushions the joint and reduces friction and wear. At some joints, articular fibrocartilage, shaped like a disc or a partial disc called a meniscus, is also present between the articulating bones. The intervertebral discs and the menisci of the knee are examples. These discs and menisci help to distribute forces evenly over the joint surfaces and absorb shock at the joint. © Body Scientific International Figure 4.31 Examples of the six different types of diarthroses. Which of these six types of joints is the most freely movable? Ball-and-socket joint (humeroscapular) Head of humerus Scapula Hinge joint (humeroulnar) Humerus Ulna Pivot joint (radioulnar) Radius Ulna Gliding joint (intercarpal) Carpal bones Saddle joint (trapeziometacarpal) Carpal bone Metacarpal bone Condylar joint (metacarpophalangeal) Metacarpal bone Phalanx Copyright Goodheart-Willcox Co., Inc.