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Chapter 10 The Muscular System Part 1 ehow.com Objectives • Know the various functions of muscle • Know the structure of muscle and the various shapes muscles form • Understand how muscles attach to bone and what origin and insertion describe creatingacomic.com • Understand how muscles fit into functional groups • Know how muscles are named Functions • Produces movement • Posture and Stability • Control of body opening and passages • Generates heat home-gym-fitness-equipment.co.uk Structure • Macro to micro – Epimysium – Fascicles • Wrapped by perimysium training.seer.cancer.gov – Muscle fibers (cells) • Wrapped by endomysium – Myofibrils • Contractile element faculty.etsu.edu Muscle Shapes • Determined by the orientation of the fascicles • Five main shapes – Fusiform – Parallel – Triangular • convergent – Pennate • Unipennate • Bipennate • Multipennate – Circular classes.midlandstech.com 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 – Retinaculum – band of connective tissue which tendons pass through – Direct • Muscle appears to be directly connected to the muscle 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 Functional Groups of Muscles • Action – the effect produced by a muscle – To move or not to move • Four categories (based on action) – Prime mover (agonist) • Produces most of the force during a joint action – Synergist • Aids the prime mover by having similar effect on joint or stabilizing and focusing action of prime mover – Antagonist • Opposes the prime mover – Fixator • Muscle that prevents a bone from moving Intrinsic and Extrinsic Muscles • Intrinsic muscles – Contained entirely within a specific region • Origin and insertion within same region • Extrinsic muscles – Have origin and insertions in different regions • Innervation – Spinal nerves – below the neck – Cranial nerves – head and neck Naming Muscles • Named according to various descriptive criteria – Location of muscle – indicate the bone or body region muscle associated with • Temporalis, intercostals – Shape of the muscle • Trapezius, deltoid Naming Muscles – Relative size of muscle • Maximus, minimus, longus (long), brevis (short) – Direction of muscle fibers • Named in relation to a line running the length of the body • Rectus, transverse, oblique – Number of origins (heads) • Bi, tri, and quad Naming Muscles – Location of attachments – named according to their points of origin and insertion • Sternocleidomastoid • Origin is always first – Action – named according to the effect of the muscle • Flexor, extensor, adductor
