194 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. posterior medial and lateral femoral condyles. The underlying soleus extends from the fibula and tibia. Both muscles insert on the calcaneus via the Achilles tendon. The three branches of the fibularis muscle are the longus, brevis, and tertius. These muscles connect the fibula to the metatarsals and assist with plantar flexion and eversion. Dorsiflexion is produced by the tibialis anterior and extensor digitorum longus on the anterior aspect of the lower leg. The tibialis anterior, connecting the tibia to the first cuneiform and first metatarsal, also acts to invert the foot. The extensor digitorum longus, extending from the lateral tibia and fibula to the metatarsals, also contributes to eversion. As discussed throughout the sections on the upper and lower limbs, many superficial muscles are readily palpable when tensed. The superficial muscles of both the upper and lower extremities are displayed by the bodybuilder in Figure 6.25. The posterior group, the hamstrings, includes the biceps femoris, semimembranosus, and semitendinosus. What these muscles have in common, besides their general location and common origin on the ischial tuberosity, is strong, stringlike tendons that can be felt on either side of the back of the knee. Collectively, they are the prime flexors of the leg at the knee. The term hamstrings comes from the fact that hams consist of thigh and hip muscles, and butchers use the tendons of these muscles to hang the hams for smoking. Muscles Acting at the Ankle The primary movements occurring at the ankle are the sagittal plane motions of plantar flexion and dorsiflexion. The plantar flexors are the gastrocnemius and soleus muscles on the posterior aspect of the lower leg. The superficial gastrocnemius extends from the External obliques Rectus abdominis Trapezius Deltoid Anterior Posterior Pectoralis major Deltoid Biceps brachii Triceps brachii: lateral head long head Olecranon Brachioradialis Vastus lateralis Rectus femoris Vastus medialis Tibialis anterior Trapezius Triceps brachii Latissimus dorsi Brachioradialis Gluteus maximus Semimebranosus Semitendinosus Biceps femoris Gastrocnemius Soleus Fibularis longus Alexander Lukatskiy/Shutterstock.com Figure 6.25 Anterior and posterior views of the major superficial muscles. SECTION 6.3 REVIEW Mini-Glossary agonist-antagonist pairs pairs of muscles that cause opposing actions at a joint diaphragm a dome-shaped sheet of muscle and fibrous tissue that separates the thoracic and abdominal cavities (continued)