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PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
The Muscular System
Part B
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
08
Interactions of Skeletal Muscles
 Skeletal muscles work together or in opposition
 Muscles only pull (never push)
 As muscles shorten, the insertion generally moves
toward the origin
 Whatever a muscle (or group of muscles) does,
another muscle (or group) “undoes”
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Muscle Classification: Functional Groups
 Prime movers – provide the major force for
producing a specific movement
 Antagonists – oppose or reverse a particular
movement
 Synergists
 Add force to a movement
 Reduce undesirable or unnecessary movement
 Fixators – synergists that immobilize a bone or
muscle’s origin
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Naming Skeletal Muscles
 Location of muscle – bone or body region associated
with the muscle
 Shape of muscle – e.g., the deltoid muscle (deltoid =
triangle)
 Relative size – e.g., maximus (largest), minimus
(smallest), longus (long)
 Direction of fibers – e.g., rectus (fibers run straight),
transversus, and oblique (fibers run at angles to an
imaginary defined axis)
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Naming Skeletal Muscles
 Number of origins – e.g., biceps (two origins) and
triceps (three origins)
 Location of attachments – named according to point
of origin or insertion
 Action – e.g., flexor or extensor, as in the names of
muscles that flex or extend, respectively
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Arrangement of Fascicles
 Parallel – fascicles run parallel to the long axis of
the muscle (e.g., sartorius)
 Fusiform – spindle-shaped muscles (e.g., biceps
brachii)
 Pennate – short fascicles that attach obliquely to a
central tendon running the length of the muscle (e.g.,
rectus femoris)
 Convergent – fascicles converge from a broad origin
to a single tendon insertion (e.g., pectoralis major)
 Circular – fascicles are arranged in concentric rings
(e.g., orbicularis oris)
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Arrangement of Fascicles
Figure 10.1
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Bone-Muscle Relationships: Lever Systems
 Lever – a rigid bar that moves on a fulcrum, or fixed
point
 Effort – force applied to a lever
 Load – resistance moved by the effort
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Bone-Muscle Relationships: Lever Systems
Figure 10.2a
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Bone-Muscle Relationships: Lever Systems
Figure 10.2b
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Lever Systems: Classes
 First class – the fulcrum is between the load and the
effort
 Second class – the load is between the fulcrum and
the effort
 Third class – the effort is applied between the
fulcrum and the load
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Lever Systems: First Class
Figure 10.3a
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Lever Systems: Second Class
Figure 10.3b
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Lever Systems: Third Class
Figure 10.3c
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Major Skeletal Muscles: Anterior View
 The 40 superficial
muscles here are
divided into 10
regional areas of
the body
Figure 10.4b
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Major Skeletal Muscles: Posterior View
 The 27 superficial
muscles here are
divided into seven
regional areas of
the body
Figure 10.5b
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Muscles: Name, Action, and Innervation
 Name and description of the muscle – be alert to
information given in the name
 Origin and insertion – there is always a joint
between the origin and insertion
 Action – best learned by acting out a muscle’s
movement on one’s own body
 Nerve supply – name of major nerve that innervates
the muscle
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles of the Scalp
 Epicranius (occipitofrontalis) – bipartite muscle
consisting of the:
 Frontalis
 Occipitalis
 Galea aponeurotica – cranial aponeurosis
connecting above muscles
 These two muscles have alternate actions of pulling
the scalp forward and backward
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Frontalis
• Origin:
– cranial aponeurosis
• Insertion:
– skin of eyebrows
• Primary Action(s):
– Raises eyebrows
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Occipitalis
Origin:
Occipital bone
Insertion:
galea aponeurosis
Primary Action(s):
wrinkles brow
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Muscles of the Face
 11 muscles are involved in lifting the eyebrows,
flaring the nostrils, opening and closing the eyes and
mouth, and smiling
 All are innervated by cranial nerve VII (facial nerve)
 Usually insert in skin (rather than bone), and
adjacent muscles often fuse
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Orbicularis Oculi
• Origin:
– Frontal bone and maxilla
• Insertion:
– Tissue around eyes
• Primary Action(s):
– Blinks and closes eyes
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Orbicularis Oris
• Origin:
– Mandible and maxilla
• Insertion:
– Skin and muscle
around mouth
• Primary Action(s):
– Closes and protrudes
lips
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Zygomaticus
• Origin:
– Zygomatic bone
• Insertion:
– Skin and muscle at
corner of lips
• Primary Action(s):
– Raises corner of mouth
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Platysma
• Origin:
– Connective tissue
covering of superior chest
muscles
• Insertion:
– Tissue around mouth
• Primary Action(s):
– Pulls corners of mouth
inferiorly
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Muscles of the Face
Figure 10.6
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Muscles of Mastication
 There are four pairs of muscles involved in
mastication
 Prime movers – temporalis and masseter
 Grinding movements – pterygoids and buccinators
 All are innervated by cranial nerve V (trigeminal
nerve)
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Muscles of Mastication
Figure 10.7a
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Temporalis
• Origin:
– Temporal bone
• Insertion:
– Mandible
• Primary Action(s):
– Closes jaw
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Masseter
Origin:
–
zygomatic arch and maxilla
Insertion:
Mandible
Primary Action(s):
Closes jaw
Protraction
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Buccinator
• Origin:
– Maxilla and mandible near
molars
• Insertion:
– Orbicularis oris
• Primary Action(s):
– Compresses cheeks
• Whistling
• Holds food between
teeth during chewing
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Muscles of Mastication
Figure 10.7b
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Pterygoid
Origin:
sphenoid
Insertion:
Mandible
Primary Action(s):
Depresses mandible
Protrude mandible
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Extrinsic Tongue Muscles
 Three major muscles that anchor and move the
tongue
 All are innervated by cranial nerve XII (hypoglossal
nerve)
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Extrinsic Tongue Muscles
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Figure 10.7c
Genioglossus
Origin:
mandible
Insertion:
tongue
Primary Action(s):
Protrude, depress, draw back and down
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Styloglossus
Origin:
Temporal bone
Insertion:
Tip and side of tongue
Primary Action(s):
Retracts & elevates
tongue
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Hyoglossus
Origin:
hyoid
Insertion:
Side of tongue
Primary Action(s):
Depresses & retracts tongue
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Muscles of the Neck: Head Movements
 Major head flexor is the sternocleidomastoid
 Synergists to head flexion are the suprahyoid and
infrahyoid
 Lateral head movements are accomplished by the
sternocleidomastoid and scalene muscles
 Head extension is accomplished by the deep
splenius muscles and aided by the superficial
trapezius
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Muscles of the Neck: Head Movements
Figure 10.9a
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Muscles of the Neck: Head Movements
Figure 10.9b
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Sternocleidomastoid
• Origin:
– Sternum and clavicle
• Insertion:
– Temporal bone
• Primary Action(s):
– Flexes neck; rotates neck
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Suprahyoid
Consists of four muscles
digastric, stylohyoid, geniohyoid, and mylohyoid
Primary Action(s):
Elevates hyoid and widens esophagus during
swallowing
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Infrahyoid
Group of four pairs of muscles
in the anterior part of the
neck
Primary Action(s):
depress the hyoid bone and
larynx during swallowing
and speaking.
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Scalenes (anterior, posterior, medius)
Origin:
C2-C7
Insertion:
1st & 2nd ribs
Primary Action(s):
Lateral head movement
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Splenius capitus
Origin:
C7-T6
Insertion:
temporal and occipital bone
Primary Action(s):
Extend, rotate, and laterally flex the head
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Trapezius
Primary Action(s):
Head extension
Rotation, retraction, elevation,
and depression of scapula
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