Muscles of the Body

Chapter 11

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Objectives

• Know the five main shapes of muscle

• Understand how muscles fit into functional groups and what those functional groups are

• Know how muscles are named

Muscle Shapes• Determined by the orientation of the fascicles

• Five main shapes– Fusiform– Parallel– Triangular

• convergent

– Pennate• Unipennate• Bipennate• Multipennate

– Circularclasses.midlandstech.com

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

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