Transcript The Muscular System

Chapter 10
The
Muscular System
Part 1
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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
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• 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
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Structure
• Macro to micro
– Epimysium
– Fascicles
• Wrapped by perimysium
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– 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
– Circular
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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