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Chapter 10
Muscular System
Gross Anatomy
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Muscle Terminology & Concepts
Tendon – connective tissue structure attaching muscle to bone
(and occasionally to other connective tissue)
Aponeurosis – a broad, sometimes fan-like tendon
Antagonists – two (or more) muscles whose actions are opposites
of each other.
e.g. one extends a structure & its antagonist flexes the same
structure
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Muscle Terminology & Concepts
Muscles generally attach to two structures, one stationary and one
moveable
Origin – the attachment end of the muscle that is most stationary
Insertion – the attachment end of the muscle that is most
moveable
Belly – the large portion of the muscle between origin & insertion
Action – the movement performed by the muscle
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Muscle Terminology & Concepts
Prime Mover – a muscle that performs most of the movement at
a joint
Fixator – a muscle that stabilizes a joint
e.g. Flexor carpi radialis & f.c. ulnaris stabilize the wrist while
fingers extend
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Naming Muscles
Muscles may be named for their:
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Location
Size
Shape
Orientation
Origin &/or Insertion
# of heads
Function
see 309-310 for examples of these
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Muscle Shapes
Pennate – feather shaped. These muscles have fascicles arranged like the
barbs of a feather around a tendon
Advantage: allows more fascicles to be attached to the tendon for a stronger pull!
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Additional Muscle Shapes
Circular – fascicles arranged in a circle, usually around an
opening. These usually close the opening. Commonly called
sphincters.
Parallel – fascicles arranged along the long axis of muscle.
Advantage: ability to shorten along much of their length.
Convergent – often fan shaped these muscles have a wide base
and a narrow insertion. Can exert more force than a parallel
muscle.
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Yes, we just saw this one
described as a multipinnate
it is both…
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Movement as Muscles Pull
Muscles pull (P)
Bones serve as levers (L)
The levers pivot around a fulcrum (F)
moving a weight (W)
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Class I Lever
Fulcrum located between the force
(pull) and the weight
similar to a seesaw
pull down on one side,
other side raises
Tilting head with muscles at back of
neck uses this method
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Class II Lever
Weight located between the pull and
the fulcrum
similar to a wheel barrow
Standing on tiptoe uses calf muscles
in this fashion
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Class II Lever
Pulling force is between fulcrum &
weight.
Similar to using a shovel
Disadvantage - can’t lift as large
weights
Advantage – can move moderate
weights over greater distances
Most common arrangement in body
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Lab Book
Review muscles listed in lab book
We will look in detail
in the coming days
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