Microscopic Anatomy and Organization of Skeletal Muscle EX 14 Microscopic Anatomy and Organization of Skeletal Muscle

Skeletal Muscle Most numerous Voluntary Striated Gives you shape, allows for facial expressions, movement, and manipulation

Cells of the Skeletal Muscle Long cylindrical cells called fibers Multinucleated Composed of myofibrils Myofilaments Made of actin and myosin alternating to produce the banding pattern (I and A bands) Sacrolema- “plasma membrane” Sacroplasm- “cytoplasm”

Skeletal Muscle Fibers Figure 10–2a The Formation of a Multinucleate Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–2 The Formation of a Multinucleate Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Sarcomeres Contractile units Made up of bundles of myofibrils Extend from middle of I band to middle of next myofibril

Organization of Skeletal Muscle Cells into Muscles Endomysium – areolar connective tissue sheath that covers muscle fibers Perimysium – encloses sheathed muscle Fascicle-bundle of perimysium Epimysium-bundle of fasciles Epimysium blend into deep fascia Fascia blends into tendons

Skeletal Muscle Structures Figure 10–1 The Organization of Skeletal Muscles. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tendons provide durability and conserve space Provide route of entry for blood vessels

Neuromuscular Junction Junction between a nerve fiber and a muscle cell Axons stimulate many muscle fibers Both neuron and muscle fibers make up the motor unit Neurotransmitters cause a change in Na and K concentration which causes muscle contraction