8: The Axial Muscles
Skeletal muscle is found attached to bones. It consists of long multinucleate fibers. The fibers run the entire length of the muscle they come from and so are usually too long to have their ends visible when viewed under the microscope. The fibers are relatively wide and very long, but unbranched . Fibers are not individual cells, but are formed from the fusion of thousands of precursor cells. This is why they are so long and why individual fibers are multinucleate (a single fiber has many nuclei). The nuclei are usually up against the edge of the fiber. There are striations in skeletal muscle. These are alternating dark and light bands perpendicular to the edge of the fiber that are present all along the fiber.
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- 8.1: The Muscles of the Head and Neck
- This page details the key muscles of the head and neck, including the platysma, sternocleidomastoid, epicranius, buccinator, masseter, and zygomaticus. Each muscle's function is described: the platysma aids jaw movement, the sternocleidomastoid enables head rotation, the epicranius covers the scalp, the buccinator compresses cheeks, the masseter closes the jaw, and the zygomaticus elevates the mouth. Additionally, the page provides exercises to help identify these muscles.
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- 8.2: The Muscles of the Trunk
- This page offers an overview of major muscles in the trunk, arms, and legs, detailing their locations and popular names among gym-goers. It covers upper body muscles such as deltoids, pectoralis major, latissimus dorsi, trapezius, and abdominal muscles like the obliques and rectus abdominis. The serratus anterior muscle is also mentioned. The text includes figures and poses questions for further exploration in a lab exercise.
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- 8.3: Exercises
- This page provides instructions for a laboratory exercise aimed at identifying components of muscle tissue, including epimysium, perimysium, endomysium, muscle fascicles, and fibers. Participants will observe a skeletal muscle tissue slide, draw and label features, and note their visual characteristics. The exercise involves identifying muscle origins and insertions, categorizing them as extensors or flexors, and requires documenting magnification details and tissue sources.
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- 8.4: MODELS- Head and Neck and Torso
- This page offers a comprehensive guide to human muscles, organized by function and location. It details muscles involved in facial expressions, the head, vertebral column, abdominal wall, thoracic and shoulder regions, and arm movements, providing each muscle's name, actions, origins, and insertions. Notable muscles like the frontalis, sternocleidomastoid, and pectoralis major are emphasized for their significance in movement and structural support.