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Chapter 10 Skeletal Muscle Tissue ehow.com Objectives • Know the various functions of muscle • Know the macroscopic and microscopic arrangement of skeletal muscle • Understand how muscles attach to bone and what origin and insertion describe • Know the types of skeletal muscle fibers • Know what muscular dystrophy is Functions and Characteristics • Produces movement • Contractility • Maintains posture • Excitability • Joint stability • Extensibility • Generates heat • Elasticity Muscle Tissue Types • Skeletal muscle – Allows for movement • Smooth muscles – Found in the walls of hollow vicseral organs • Cardiac muscles – Only found within walls of heart Structure • Macro to micro – Epimysium • Dense irregular CT – Fascicles • Wrapped by perimysium training.seer.cancer.gov – Muscle fibers (cells) • Wrapped by endomysium – Myofibrils • Contractile element faculty.etsu.edu Microanatomy of Myofibril • Dark band – A band • Light band – I band • H zone • Z disc – Sarcomere • Titin – Largest protein in body – Stabilizes thick fillaments – Gives muscle elasticity http://legacy.owensboro.kctcs.edu/gcaplan/anat/images/Image286.gif The Sarcomere • Functional unit • Microfilaments – Actin • Troponin • Tropomyosin scioly.org – Myosin • Heads contain two binding sites • Actin and ATPase people.eku.edu Innervation of Skeletal Muscle • Motor neuron and neuromuscular junction Muscle Contractions • Concentric – Contraction that occurs when muscle shortens and causes a movement • Eccentric – Contraction the occurs while muscle lengthens Muscle Attachments • Two types of attachments – Indirect • Muscles connected to bones via visible tendons • Tendons merge with periosteum and bony matrix – Aponeurosis – broad sheet-like tendon – Direct • Muscle appears to be directly connected to the bone with little space between them – Small microscopic gaps bridged by collagen fibers – Not always to bone, may be to fascia or the skin Muscle Attachments scapula.pl Origins and Insertions • Origin – bony site of attachment that remains more stationary • Insertion – bony site of attachment that is more mobile • Belly – thick portion of muscle between attachment sites Types of Muscle Fibers Slow-oxidative fibers (SO) • Thin red fibers Fast-glycolytic fibers (FG) • Thick white fibers – Rich in myoglobin – Little myoglobin • Rely on aerobic metabolism • Rely on glycolysis • Slow twitch: endurance, long duration contraction • Fast twitch: strength, short duration contraction: Fast-oxidative fibers (FO) • Intermediate fibers • Rich in myoglobin Disorders of Skeletal Muscle • Muscular Dystrophy – Inherited disorder • Dysfunction in the protein dystrophin – Muscular tissue is replaced by fat and CT
