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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
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