The Muscular System

Part 1

Chapter 10

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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

• Understand how muscles fit into functional groups

• Know how muscles are named

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Functions

• Produces movement

• Posture and Stability

• Control of body opening and passages

• Generates heathome-gym-fitness-equipment.co.uk

Structure• Macro to micro– Epimysium

– Fascicles• Wrapped by perimysium

– Muscle fibers (cells)• Wrapped by endomysium

– Myofibrils• Contractile element

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Muscle Shapes• Determined by the orientation of the fascicles

• Five main shapes– Fusiform– Parallel– Triangular

• convergent– Pennate

• Unipennate• Bipennate• Multipennate

– Circularclasses.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

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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