Chapter 4 The Skeletal System 147 The Leg The single bone of the upper leg, or thigh, is the femur (FEE-mer), which is the longest and strongest bone in the body. Figure 4.25 shows the anatomical features of the femur. The head of the femur fits snugly into the acetabulum of the hip, making the joint extremely stable. The most vulnerable part of the femur is the neck, which is the site where most hip fractures occur. The lower leg has two bones: the tibia and fibula (Figure 4.26). The thick, strong tibia (TIB-ee-a)—or shinbone—is the bone that bears most of the weight of the body above it. Unlike the radius in the forearm, the fibula (FIB-yoo-la) has no special motion capability and serves primarily as a site for muscle attachments. The fibula is not part of the articulation with the femur at the knee joint, but the distal end of the fibula has a bony prominence called the lateral malleolus (mal-LEE-oh-lus), which you can readily touch and feel on the lateral (outer) side of the ankle. Like the radius and ulna in the forearm, the tibia and fibula are connected along their lengths by an interosseous membrane, and they articulate at both ends of the fibula. The patella (pa-TEHL-a), or kneecap, is a small, flat, triangular-shaped bone that protects the front of the knee. The articulations of the bones of the leg and ankle are summarized in Figure 4.27. © Body Scientific International Figure 4.24 Bones of the pelvis. Why are these bones important when classifying skeletons? Iliac crest Pubis Ischial spine Ischial tuberosity A Pelvis B Coxal bone, right lateral view Coxal bone Ischium Acetabulum Ilium Sacroiliac joints Obturator foramen Coccyx Sacrum Pubis symphysis © Body Scientific International Figure 4.25 The right femur and the patella. Although the femur is the strongest bone in the body, one part is vulnerable to fracture. What is the most vulnerable part of the femur? Lateral condyle Medial condyle Shaft Neck Head Articular facets A Anterior view B Posterior view Greater trochanter Greater trochanter Patellar surface Patella Copyright Goodheart-Willcox Co., Inc.