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Muscles
Chapter 10
Fasicle
arrangement
Parallel Muscle Tension
• Depends on total number of
myofibrils
• Directly relates to cross section of
muscle
• 1 in.2 (6.45 cm2) of cross section
develops 50 lb (23 kg) of tension
Parallel Muscles
Figure 11–1a
Convergent Muscles
• A broad area converges on
attachment site (tendon, aponeurosis,
or raphe)
• Muscle fibers pull in different
directions, depending on stimulation
• e.g., pectoralis muscles
Convergent Muscles
Pennate Muscles
• Form an angle with the tendon
• Do not move as far as parallel muscles
• Contain more myofibrils than parallel
muscles
• Develop more tension than parallel
muscles
Pennate Muscles
Figure 11–1c, d, e
Circular Muscles
• Also called sphincters
• Open and close to guard entrances of
body
• e.g., obicularis oris
Circular Muscles
Levers
• Mechanically, each bone is a lever (a
rigid, moving structure):
– and each joint a fulcrum (a fixed point)
• Muscles provide applied force (AF):
– required to overcome resistance (R)
Functions of a Lever
• To change:
– direction of an AF
– distance and speed of movement
produced by an AF
– effective strength of an AF
3 Classes of Levers
• Depend on the relationship between
applied force, fulcrum, and
resistance:
– first class
– second class
– third class
First-Class Levers
Figure 11–2a
First-Class Levers
• Seesaw is an example
• Center fulcrum between applied force
and resistance
• Force and resistance are balanced
Second–Class Levers
Second-Class Levers
• Wheelbarrow is an example
• Center resistance between applied
force and fulcrum
• A small force moves a large weight
Third-Class Levers
Figure 11–2c
Third-Class Levers
• Most common levers in the body
• Center applied force between
resistance and fulcrum
• Greater force moves smaller
resistance
• Maximizes speed and distance
traveled
Physics of levers
Origins and Insertions
• Muscles have 1 fixed point of
attachment (origin) and 1 moving point
of attachment (insertion)
• Most muscles originate or insert on
the skeleton
• Origin is usually proximal to insertion
Actions
• Movements produced by muscle
contraction
• Body movements
– e.g., flexion, extension, adduction, etc.
• Described in terms of bone, joint, or
region
Descriptive Names
for Skeletal Muscles
1.
2.
3.
4.
5.
6.
Location in the body
Origin and insertion
Fascicle organization
Relative position
Structural characteristics
Action
Muscles:
anterior
Muscles:
posterior
Muscles of Facial Expression
Figure 11–4a
Muscles of Facial Expression
Figure 11–4b
Extrinsic Eye Muscles
• Also called extra-ocular muscles
Figure 11–5a, b
Muscles of Mastication
Anterior Muscles of the Neck
Figure 11–9
Muscles of
the Vertebral
Column
Figure 11–10a
Muscles of the
Vertebral
Column
Oblique and Rectus Muscles
• Lie within the body wall
Figure 11–11a, b
Oblique and Rectus Muscles
Figure 11–11a, c
The
Appendicular
Muscles
Figure 11–13a
The
Appendicular
Muscles
Muscles that Move the Arm
Figure 11–15a
Muscles that Move the Arm
Muscles that
Move
the Forearm
and Hand
Figure 11–16a
Muscles that
Move
the Forearm
and Hand
Figure 11–16b
Muscles that Move the Hand and Fingers
Muscles that Move the Hand and Fingers
Muscles that Move the Thigh
Figure 11–19a, b
Muscles that Move the Thigh
Muscles that
Move the Leg
Figure 11–20a
Muscles that
Move the Leg
Figure 11–20b, c
Muscles that Move the Foot and Toes
Muscles that Move the Foot and Toes
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