Muscles are organs, and as such they contain other types of tissues, such as nervous tissue, blood vessels, and connective tissue. Connective tissue is essential to the organization of the fibers within a muscle (Fig. 1.7). First, each fiber is surrounded by a thin layer of areolar connective tissue called the endomysium. Blood capillaries and nerve fibers reach each muscle fiber by way of the endomysium. Second, the muscle fibers are grouped into bundles called fascicles. The fascicles have a sheath of connective tissue called the perimysium.Finally, the.muscle itself is covered by a connective tissue layer called the epimysium. The epimysium becomes a part of the fascia, a layer of fibrous tissue that separates muscles from each other (deep fascia) and from the skin (superficial fascia). Collagen fibers of the epimysium continue as a strong, fibrous tendon that attaches the muscle to a bone. The epimysium merges with the periosteum of the bone.
Functions of Skeletal Muscles
Skeletal muscles support the body
Skeletal muscle contraction opposes the force of gravity and allows us to remain upright. Some skeletal muscles are serving this purpose even when you think you are relaxed.
Skeletal muscles make bones and other body parts move
Muscle contraction accounts not only for the movement of limbs but also for eye movements, facial expressions, and breathing.
Skeletal muscles help maintain a constant body temperature
Skeletal muscle contraction causes ATP to break down, releasing heat that is distributed about the body. Skeletal muscle contraction assists movement in cardiovascular and lymphatic vessels
The pressure of skeletal muscle contraction keeps blood moving in cardiovascular veins and lymph moving in lymphatic vessels.
Skeletal muscles help protect internal organs and stabilize joints
Muscles pad the bones that protect organs, and they have tendons that help hold bones together at joints.
