Chapter 10 Muscular System: Gross Anatomy AP1 Chapter 10 1
Jan 01, 2016
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Chapter 10 Outline
I. General PrinciplesA. Muscle Shapes
B. Nomenclature
C. Movements accomplished by muscles
D. Muscle Anatomy
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I. General Principles• Most skeletal muscles
extend from one bone to another & cross at least 1 joint.– Some aren’t facial muscles
attach to bone on one end & the skin on the other (moves the face)
• Muscle contraction causes most body movements by pulling 1 bone toward the other across a movable joint.
• ACTION: movement accomplished by a muscle when it contracts
Fig 10.27Pg 353
Fig 10.15Pg 339
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ener
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Pg 321 Figure 10.1
Muscle Terminology• Origin:
– (fixed end, or head) usually both the most stationary & most proximal end of the muscle. (some have multiple)
• Insertion:– (Mobile end) usually the most distal
end attached to the bone undergoing the most movement.
• Belly:– Region between the origin &
insertion
• Tendon:– Responsible for attaching muscle to
bone– Long cable-like structures; broad
sheet-like structures called aponeuroses; or short, almost non-existent structures
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I. General Principles • Muscles (much like the
movement discussed in Chapter 8) oppose each other.
• Agonist:– Muscle accomplishing 1
movement (biceps brachii)
• Antagonist:– Muscle opposing the
movement of the agonist (Triceps brachii).
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I. General Principles• Muscles also tend to functions in groups to
accomplish specific movements:– Synergists: members of a group of muscles working
together to prod a mvmt.– Prime Mover: the muscle responsible for the major role
accomplishing the desired movement– Fixators: muscles that holds one bone in place relative
to the body while (normally) a more distal bone is moved– Example:
• Synergists: biceps brachii & brachialis fxn in elbow flexion• Prime mover: Brachialis• Fixators: muscles in the scapula to keep shoulder stationary
while humerus is moving
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A. Muscle Shapes
• Shape & size of a muscle influence the degree to wh/ it can contract & amount of force generated.
• 3 major classes based on fasciculi orientation:1. Pennate
2. Straight
3. Orbicular
Pg 322Fig 10.2
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A. Muscle Shapes1. Pennate
– Bipennate:• Fasciculi arranged like the
barbs of a feather on 2 sides of a common tendon
– Semipennate:• All fasciculi are on 1 side of
the tendon (unipennate)
– Multipennate• Fasciculi arranged at many
places around the central tendon
• Ex/muscles extending from the knee
Pg 322Fig 10.2
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A. Muscle Shapes
2. Straight– Fasciculi are arranged
parallel to the long axis of the muscle.
– Result:• Muscles shorten to a greater
degree because of the direct line to the tendon, but contract with less force b/c fewer total fascicles are attached to the tendon.
• Hyoid muscles
3. Orbicular– Fasiculi are arranged in a
circle around an opening & act as sphincters to close and opening
Pg 322Fig 10.2
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Muscles are named according to:
A. Location: – Examples: Pectoralis (chest) ; Gluteus (Buttock); Brachial (arm)
B. Size– Gluteus maximus (Large); Gluteus minimus (Small); Longus (long); Brevis
(short)
C. Shape– Deltoid (triangular); Quadratus (rectangular); teres (round)
D. Orientation of fasciculi– Rectus (Straight); Oblique (slanting or inclined; diagonal)
E. Origin & insertion– Brachioradialis (origin in arm [brachii] and insertion at radius)
F. Number of heads– Biceps have 2 heads (Triceps 3 heads)
G. Functions– Adductor moves toward midline– Abductor moves away from midline– Masseter Chews
B. Nomenclature
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C. Movements accomplished by muscles• Contracting muscles
generate force that acts on bones (Levers) across joints (Fulcrums) to create movement.
• 3 classes1. Class I
2. Class II
3. Class III
Resistance
Load (L)
Lever Systems & Leverage• Lever
– Ridged structure that can move around a fixed point
• Fulcrum– The Fixed Point (Elbow)
• Effort (Pull)– Causes the movement– Contraction of the Bicep
• Resistance (Weight)– Opposes the movement
Resistance
Load (L)