148 Introduction to Anatomy & Physiology the metacarpals of the hand. Like the fingers, each toe is comprised of three phalanges, and like the thumb, the big toe has only two phalanges. The toes function by increasing the area of the foot during weight-bearing activities such as walking and running—thereby increasing body stability. The configuration of the metatarsal bones forms two important arches (Figure 4.29). The longitudinal arch runs lengthwise from the calcaneus to the heads of the metatarsals. The transverse arch runs sideways (perpendicular to the longitudinal arch), and in most people causes The Ankle and Foot The ankle and foot serve the critically important functions of supporting body weight and enabling locomotion. The foot is so well designed that it assists with walking and running by acting like a spring that stores and releases energy. The hindfoot is constructed of tarsal (TAR-sal) bones, with the two largest, the talus (TAY-lus) and calcaneus (kal-KAY-nee-us)—or heel bone—bearing most of the weight of the body (Figure 4.28). The five metatarsal (meht-a-TAR-sal) bones that support the midfoot region are similar to © Body Scientific International Figure 4.26 The right tibia and fibula, anterior and posterior views. Medial condyle Lateral condyle Head of fibula Lateral malleolus Tibial tuberosity Interosseous membrane Tibia Fibula Medial malleolus Anterior view Posterior view Proximal tibiofibular joint Intercondylar eminence Lateral surface Distal tibiofibular joint Lateral malleolus Anterior crest Apex Articulating Bones of the Leg and Ankle Joint Notched Bone or Socket Joining Bone or Region iliofemoral (hip) joint acetabulum femur tibiofemoral (knee) joint tibia femur patellofemoral joint patella anterior knee tibiofibular joints (proximal and distal) tibia fibula Figure 4.27 Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co., Inc.