Chapter 10
Lecture Outline
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1
Introduction
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• Muscles constitute nearly
half of the body’s weight and
are of central interest in
several fields of health care
and fitness
Figure 10.5a
10-2
The Structural and Functional
Organization of Muscles
• Expected Learning Outcomes
– Describe the varied functions of muscles.
– Describe the connective tissue components of a muscle
and their relationship to the bundling of muscle fibers.
– Describe the various shapes of skeletal muscles and
relate this to their functions.
– Explain what is meant by the origin, insertion, belly,
action, and innervation of a muscle.
10-3
The Structural and Functional
Organization of Muscles
(Continued)
– Describe the ways that muscles work in groups to aid,
oppose, or moderate each other’s actions.
– Distinguish between intrinsic and extrinsic muscles.
– Describe, in general terms, the nerve supply to the
muscles and where these nerves originate.
– Explain how the Latin names of muscles can aid in
visualizing and remembering them.
10-4
The Structural and Functional
Organization of Muscles
• About 600 human skeletal muscles
• Constitute about half of our body weight
• Three kinds of muscle tissue
– Skeletal, cardiac, smooth
• Specialized for one major purpose
– Converting the chemical energy in ATP into the
mechanical energy of motion
• Myology—the study of the muscular system
10-5
The Functions of Muscles
• Muscle functions include: movement, stability,
control of openings, heat production, and
glycemic control
• Movement
– Move from place to place; move body parts; move body
contents in breathing, circulation, and digestion
– In communication: speech, writing, facial expressions
and other nonverbal communications
• Stability
– Maintain posture by preventing unwanted movements
– Antigravity muscles: prevent us from falling over
– Stabilize joints by maintaining tension
10-6
The Functions of Muscles
• Control of openings and passageways
– Sphincters: internal muscular rings that control the
movement of food, blood, and other materials within body
• Heat production by skeletal muscles
– As much as 85% of our body heat
• Glycemic control
– Muscles absorb and store glucose which helps regulate
blood sugar concentration within normal range
10-7
Connective Tissues of a Muscle
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Tendon
Fascia
Skeletal
muscle
Muscle
fascicle
Nerve
Blood vessels
Epimysium
Perimysium
Endomysium
Muscle fiber
Muscle fascicle
Figure 10.1a
Perimysium
Muscle fiber
(a)
10-8
Connective Tissues and Fascicles
• Endomysium
– Thin sleeve of loose connective tissue around each fiber
– Allows room for capillaries and nerve fibers
– Provides chemical environment for muscle fiber
• Perimysium
– Thicker layer of connective tissue that wraps fascicles
• Fascicles: bundles of muscle fibers wrapped together
– Carries nerves, blood vessels, and stretch receptors
• Epimysium
– Fibrous sheath surrounding entire muscle
– Outer surface grades into fascia; inner surface projections
form perimysium
• Fascia
– Sheet of connective tissue that separates neighboring
muscles or muscle groups from each other and the
subcutaneous tissue
10-9
Connective Tissues and Fascicles
Figure 10.1c
10-10
Fascicles and Muscle Shapes
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Unipennate
Triangular
Bipennate
Parallel
Multipennate
Fusiform
Tendon
Circular
Belly
Pectoralis major
Tendon
Palmar interosseous
Rectus femoris
Rectus abdominis
Biceps brachii
Deltoid
Figure 10.2
Orbicularis oculi
• Strength of a muscle and the direction of its pull are
determined partly by the orientation of its fascicles
10-11
Fascicles and Muscle Shapes
• Fusiform muscles—thick in the middle and tapered at
each end
• Parallel muscles—uniform width and parallel fascicles
• Triangular (convergent) muscles—broad at one end
and narrow at the other
• Pennate muscles—feather shaped
- Unipennate—fasciles approach tendon from one side
- Bipennate—fascicles approach tendon from both sides
- Multipennate—bunches of feathers converge to single point
• Circular muscles (sphincters)—form rings around
body openings
10-12
Muscle Compartments
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Anterior
Lateral Medial
Posterior
Key
Anterior compartment
Lateral compartment
Posterior compartment,
deep layer
Posterior compartment,
superficial layer
Tibia
Fibula
Interosseous
membrane
Artery, veins,
and nerve
Intermuscular
septa
Fasciae
Subcutaneous
fat
Figure 10.3
• Muscle compartment—a group of functionally related
muscles enclosed by fascia
– Also contains nerves and blood vessels that supply the muscle group
• Intermuscular septa are very thick fascia that separate one
compartment from another
10-13
Muscle Attachments
• Indirect attachment to bone
– Tendons connect muscle to bone
• Collagen fibers of the endo-, peri-, and epimysium
continue into the tendon and from there into periosteum
and matrix of bone
• Aponeurosis—tendon is a broad, flat sheet (palmar
aponeurosis)
• Retinaculum—connective tissue band that tendons from
separate muscles pass under
• Direct (fleshy) attachment to bone
– Little separation between muscle and bone
– Muscle seems to emerge directly from bone
10-14
Muscle Origins and Insertions
• Origin
– Bony attachment at
stationary end of
muscle
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Origins
Origins
Humerus
Scapula
Bellies
• Belly
– Thicker, middle region
of muscle between
origin and insertion
• Insertion
– Bony attachment to
mobile end of muscle
Extensors:
Triceps brachii
Long head
Flexors:
Biceps brachii
Brachialis
Lateral head
Insertion
Radius
Ulna
Insertion
Figure 10.4
10-15
Muscle Origins and Insertions
• Some anatomists prefer nontraditional
descriptions of attachments by proximal vs.
distal or superior vs. inferior
• Some muscles insert not on bone but on the
fascia or tendon of another muscle or on
collagen fibers of the dermis
– Example: many facial muscles insert in the skin
10-16
Functional Groups of Muscles
• Action—effect produced by a muscle to produce or
prevent movement
• Four categories of muscle action: prime mover,
synergist, antagonist, and fixator
– Prime mover (agonist)
• Muscle that produces most of force during a particular
joint action
– Synergist: muscle that aids the prime mover
• May contribute additional force, modify the direction of
movement, or stabilize a nearby joint
10-17
Functional Groups of Muscles
(Continued)
– Antagonist: opposes the prime mover
• Prevents excessive movement
• Sometimes relaxes to give prime mover control over
an action
• Antagonistic pairs—muscles that act on opposite
sides of a joint
– Fixator: muscle that prevents movement of bone
10-18
Functional Groups of Muscles
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Origins
Origins
For elbow flexion:
•
•
Flexors:
•
Biceps brachii
Brachialis
•
Humerus
Scapula
Bellies
Extensors:
Triceps brachii
Long head
Lateral head
Prime mover—brachialis
Synergist—biceps brachii
Antagonist—triceps brachii
Fixator—muscle that holds
scapula firmly in place
– Rhomboids
Insertion
Radius
Ulna
Insertion
Figure 10.4
10-19
Intrinsic and Extrinsic Muscles
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• Intrinsic muscle—
entirely contained
Common
flexor
within a region,
tendon
such as the hand
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Flexor
digitorum
superficialis
Flexor
pollicis longus
Flexor
digitorum
superficialis
tendons
Flexor
digitorum
profundus
tendons
(b) Intermediate flexor
Figure 10.28b
– Both origin and
insertion there
Tendon sheath
First dorsal
interosseous
Tendon of flexor
digitorum profundus
Adductor
pollicis
Tendon of flexor
digitorum superficialis
Lumbricals
Opponens
digiti minimi
Flexor pollicis
brevis
Flexor digiti
Abductor pollicis
brevis
Abductor digiti
minimi
• Extrinsic
muscle—acts on a
designated region,
but has its origin
elsewhere
Tendon of flexor
pollicis longus
Opponens pollicis
Flexor retinaculum
Tendons of:
Abductor pollicis
longus
Flexor carpi
radialis
Flexor pollicis
longus
Tendons of:
Flexor carpi ulnaris
Flexor digitorum
superficialis
Palmaris longus
(a) Palmar aspect, superficial
Figure 10.31a
– Fingers: extrinsic
muscles in the
forearm
10-20
Muscle Innervation
• Innervation of a muscle—refers to the identity of
the nerve that stimulates it
– Knowing innervation enables diagnosis of nerve, spinal
cord, and brainstem injuries from muscle tests
• Spinal nerves arise from the spinal cord
–
–
–
–
Emerge through intervertebral foramina
Immediately branch into posterior and anterior rami
Innervate muscles below the neck
Plexus: web-like network of spinal nerves adjacent to
the vertebral column
10-21
Muscle Innervation
• Cranial nerves arise from the base of the brain
– Emerge through skull foramina
– Innervate the muscles of the head and neck
– Numbered CN I to CN XII
10-22
Blood Supply
• Muscular system receives about 1.24 L of
blood per minute at rest (one-quarter of the
blood pumped by the heart)
• During heavy exercise, total cardiac output
rises and the muscular system’s share is
more than three-quarters (11.6 L/min)
• Capillaries branch extensively through the
endomysium to reach every muscle fiber
10-23
How Muscles Are Named
• Latin names
– Depressor labii inferioris, flexor digiti minimi brevis
• Describes distinctive aspects of the
structure, location, or action of a muscle
• Footnotes throughout chapters show
interpreted names of muscles
• Pronunciation of muscles available online at
www.aprevealed.com
10-24
The Muscular System
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Superficial
Deep
Frontalis
Orbicularis oculi
Masseter
Zygomaticus major
Orbicularis oris
Sternocleidomastoid
Platysma
Trapezius
Pectoralis minor
Deltoid
Coracobrachialis
Pectoralis major
Serratus anterior
Brachialis
Biceps brachii
Rectus abdominis
Supinator
Flexor digitorum
profundus
Flexor pollicis longus
Brachioradialis
Flexor carpi radialis
Transverse abdominal
External abdominal
oblique
Tensor
fasciae latae
Internal abdominal
oblique
Pronator quadratus
Adductor longus
Sartorius
Adductors
Rectus femoris
Vastus lateralis
Vastus lateralis
Vastus intermedius
Gracilis
Vastus medialis
Fibularis longus
Gastrocnemius
Tibialis anterior
Soleus
Extensor digitorum longus
Extensor digitorum
longus
Figure 10.5b
Figure 10.5a
(a) Anterior view
10-25
A Learning Strategy
• Examine models, cadavers, dissected animals,
or a photographic atlas
• Palpate muscles on yourself if possible
• Locate origins and insertions of muscles on an
articulated skeleton
• Study derivation of each muscle name
– Usually describes the muscle’s location, appearance,
origin, insertion, or action
• Say the names aloud to yourself or study
partner, and spell them correctly
10-26
Muscles of the Head and Neck
• Expected Learning Outcomes
– Name and locate the muscles that produce facial
expression.
– Name and locate the muscles used for chewing and
swallowing.
– Name and locate the neck muscles that move the
head.
– Identify the origin, insertion, action, and innervation of
any of these muscles.
10-27
Muscles of Facial Expression
• Muscles that insert in the dermis and
subcutaneous tissues
• Tense the skin and produce facial
expressions
• Innervated by facial nerve (CN VII)
• Paralysis causes face to sag
• Found in scalp, forehead, around the eyes,
nose, and mouth, and in the neck
10-28
Muscles of Facial Expression
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Superficial
Deep
Galea aponeurotica
Frontalis
Corrugator supercilii
Orbicularis oculi
Nasalis
Levator anguli oris
Levator labii superioris
Zygomaticus minor
Zygomaticus major
Masseter
Risorius
Buccinator
Modiolus
Orbicularis oris
Depressor anguli oris
Mentalis (cut)
Depressor labii inferioris
Platysma
(a) Anterior view
Figure 10.8a
10-29
Muscles of Facial Expression
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Galea aponeurotica
Frontalis (cut)
Temporalis
Corrugator supercilii
Orbicularis oculi
Occipitalis
Nasalis
Levator labii superioris
Zygomatic arch
Zygomaticus minor
Zygomaticus major
Orbicularis oris
Masseter
Sternocleidomastoid
Modiolus
Levator scapulae
Risorius (cut)
Inferior pharyngeal
constrictor
Thyrohyoid
Mentalis
Depressor labii
inferioris
Depressor anguli oris
Sternothyroid
Omohyoid
Sternohyoid
(b) Lateral view
Figure 10.8b
Buccinator
10-30
Muscles of Chewing and Swallowing
• Extrinsic muscles of the tongue
–
–
–
–
Tongue is very agile organ
Pushes food between molars for chewing (mastication)
Forces food into the pharynx for swallowing (deglutition)
Crucial importance to speech
• Intrinsic muscles of tongue
– Vertical, transverse, and longitudinal fascicles
Styloid process
Palatoglossus
Mastoid process
Styloglossus
Posterior belly of digastric (cut)
Superior pharyngeal constrictor (cut)
Inferior longitudinal
muscle of tongue
Stylohyoid
Middle pharyngeal constrictor
Genioglossus
Hyoglossus
Mylohyoid (cut)
Hyoid bone
Geniohyoid
Larynx
Inferior pharyngeal constrictor
Trachea
Esophagus
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Figure 10.9
10-31
Muscles of Chewing and Swallowing
• Four pairs of muscles produce
biting and chewing movements
of the mandible
–
–
–
–
–
Depression: to open mouth
Elevation: biting and grinding
Protraction: incisors can cut
Retraction: make rear teeth meet
Lateral and medial excursion: grind
food
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Temporalis
Orbicularis oris
Buccinator
Masseter (cut)
(a) Lateral view
• Temporalis, masseter, medial
pterygoid, and lateral pterygoid
Lateral pterygoid plate
Medial pterygoid plate
Lateral pterygoid muscle
Medial pterygoid muscle
• Innervated by mandibular
nerve, a branch of the
trigeminal (CN V)
Interior of oral cavity
(b) Posterior view
Figure 10.10a,b
10-32
Muscles of Chewing and Swallowing
•
•
•
•
•
•
•
Hyoid muscles—suprahyoid group
Aspects of chewing, swallowing, and vocalizing
Eight pairs of hyoid muscles associated with hyoid bone
Digastric—opens mouth widely
Geniohyoid—depresses mandible
Mylohyoid—elevates floor of mouth at beginning of swallowing
Stylohyoid—elevates hyoid
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Superficial
Suprahyoid
group
Deep
Digastric:
Anterior belly
Posterior belly
Stylohyoid
Mylohyoid
Hyoid bone
Common carotid artery
Levator scapulae
Infrahyoid
group
Internal jugular vein
Thyrohyoid
Sternohyoid
Omohyoid:
Superior belly
Inferior belly
Sternothyroid
Sternocleidomastoid
Infrahyoid
group
Clavicle
(a) Anterior view
Figure 10.11a
10-33
Muscles of Chewing and Swallowing
• Hyoid muscles—infrahyoid group
• Fix hyoid bone from below, allowing suprahyoid muscles to
open mouth
• Omohyoid—depresses hyoid after elevation
• Sternohyoid—depresses hyoid after elevation
• Thyrohyoid—depresses hyoid and elevates larynx
• Sternothyroid—depresses larynx after elevation
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Stylohyoid
Digastric (posterior belly)
Hyoglossus
Splenius capitis
Mylohyoid
Inferior pharyngeal constrictor
Digastric
(anterior belly)
Hyoid bone
Sternocleidomastoid
Trapezius
Thyrohyoid
Levator scapulae
Omohyoid
(superior belly)
Sternothyroid
Scalenes
Omohyoid (inferior belly)
Sternohyoid
(b) Lateral view
Figure 10.11b
10-34
Muscles of Chewing and Swallowing
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Styloid process
Palatoglossus
Mastoid process
Styloglossus
Posterior belly of digastric (cut)
Superior pharyngeal constrictor (cut)
Inferior longitudinal
muscle of tongue
Stylohyoid
Middle pharyngeal constrictor
Genioglossus
Hyoglossus
Mylohyoid (cut)
Hyoid bone
Geniohyoid
Larynx
Inferior pharyngeal constrictor
Trachea
Esophagus
Figure 10.9
• Pharynx: three pairs pharyngeal constrictors
– Encircle pharynx forming a muscular funnel
– During swallowing, drive food into the esophagus
10-35
Muscles Acting on the Head
• Originate on vertebral column, thoracic cage,
and pectoral girdle
• Insert on the cranial bones
• Actions
– Flexion (tipping head forward)
– Extension (holding the head erect)
– Lateral flexion (tipping head to one side)
– Rotation (turning the head to the left and right)
10-36
Muscles Acting on the Head
• Neck flexors
– Sternocleidomastoid
– Scalenes
• Neck extensors
– Trapezius
– Splenius capitis
– Semispinalis capitis
Figure 10.12
10-37
Muscles Acting on the Head
• May cause contralateral movement:
movement of the head toward the opposite
side
• May cause ipsilateral movement: movement
of the head toward the same side
10-38
Muscles of the Trunk
• Expected Learning Outcomes
– Name and locate the muscles of respiration and
explain how they affect airflow and abdominal
pressure.
– Name and locate the muscles of the abdominal wall,
back, and pelvic floor.
– Identify the origin, insertion, action, and innervation of
any of these muscles.
10-39
Muscles of the Trunk
• Three functional groups
– Muscles of respiration
– Muscles that support abdominal wall and pelvic floor
– Movement of vertebral column
10-40
Muscles of Respiration
• Breathing requires the use of muscles
enclosing thoracic cavity
– Diaphragm, external intercostal, internal intercostal,
and innermost intercostal muscles
• Inspiration—air intake
• Expiration—expelling air
10-41
Muscles of Respiration
• Other muscles of chest and abdomen that
contribute to breathing
–
–
–
–
Sternocleidomastoid, scalenes of neck
Pectoralis major and serratus anterior of chest
Latissimus dorsi of back
Abdominal muscles: internal and external obliques, and
transverse abdominis
– Even some anal muscles
10-42
Muscles of Respiration
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• Diaphragm—muscular
dome between thoracic and
abdominal cavities
• Muscle fascicles extend to
a fibrous central tendon
• Contraction flattens
diaphragm
Xiphoid process
of sternum
Inferior
vena cava
Ribs
Esophagus
Central
tendon
of diaphragm
Aorta
– Enlarges thoracic cavity
(inspiration)
• In relaxation of diaphragm it
rises
– Shrinks the thoracic cavity
(expiration)
Vertebral
column
(b) Inferior view of diaphragm
Figure 10.13b
10-43
Muscles of Respiration
• External intercostals
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– Elevate ribs
– Expand thoracic cavity
– Create partial vacuum causing
inflow of air
External
intercostals
• Internal intercostals
– Depresses and retracts ribs
– Compresses thoracic cavity
– Expelling air
Internal
intercostals
(a) Lateral view of intercostal muscles
• Innermost intercostals
– Same action as internal
intercostals
Figure 10.13a
10-44
Muscles of the Anterior Abdominal Wall
• Internal abdominal oblique
– Intermediate layer of lateral abdominal muscles
– Unilateral contraction causes ipsilateral rotation of waist
– Aponeurosis
• Tendons of oblique and transverse muscles
• Broad, fibrous sheets
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Subclavius
Pectoralis minor (cut)
Pectoralis minor
Internal intercostals
Serratus anterior
External intercostals
Rectus abdominis (cut)
Rectus sheath
External abdominal
oblique (cut)
Internal abdominal
oblique (cut)
Internal abdominal
oblique
Posterior wall of rectus sheath
(rectus abdominis removed)
Inguinal ligament
Transverse abdominal (cut)
(b) Deep
Figure 10.15b
10-45
Muscles of the Anterior Abdominal Wall
• Transverse abdominal
–
–
–
–
Deepest of lateral abdominal muscles
Horizontal fibers
Compresses abdominal contents
Contributes to movements of vertebral column
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Subclavius
Pectoralis minor (cut)
Pectoralis minor
Internal intercostals
Serratus anterior
External intercostals
Rectus abdominis (cut)
Rectus sheath
External abdominal
oblique (cut)
Internal abdominal
oblique (cut)
Internal abdominal
oblique
Posterior wall of rectus sheath
(rectus abdominis removed)
Inguinal ligament
Transverse abdominal (cut)
(b) Deep
Figure 10.15b
10-46
Muscles of the Anterior Abdominal Wall
• Rectus abdominis
–
–
–
–
–
Flexes lumbar region of vertebral column
Produces forward bending at the waist
Extends from sternum to pubis
Rectus sheath encloses muscle
Three transverse tendinous intersections divide rectus abdominis
into segments, sometimes called a “six pack”
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Pectoralis major
Latissimus dorsi
Serratus anterior
Tendinous
intersections
Rectus sheath (cut edges)
Rectus sheath
Transverse abdominal
Umbilicus
Internal abdominal
oblique (cut)
Linea semilunaris
Linea alba
External abdominal
oblique (cut)
Rectus abdominis
Aponeurosis of
external abdominal
oblique
Inguinal ligament
(a) Superficial
Figure 10.15a
10-47
Muscles of Back
• Back muscles extend,
rotate, and laterally
flex vertebral column
• Most prominent
superficial back
muscles:
latissimus dorsi and
trapezius
• Upper limb movement
Figure 10.17
10-48
Muscles of the Back
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• Deep muscles
• Erector spinae
– Iliocostalis, longissimus,
spinalis
– From cranium to sacrum
– Extension and lateral
flexion of vertebral column
• Semispinalis thoracis
– Extension and
contralateral rotation of
vertebral column
Superior nuchal line
Semispinalis capitis
Longissimus capitis
Splenius capitis
Semispinalis cervicis
Serratus posterior
superior
Splenius cervicis
Semispinalis
thoracis
Erector spinae:
Iliocostalis
Longissimus
Spinalis
Serratus posterior inferior
Multifidus
Internal abdominal
oblique
Quadratus lumborum
External abdominal
oblique (cut)
Figure 10.18
10-49
Muscles of the Back
(Continued)
• Quadratus lumborum
– Aids respiration
– Ipsilateral flexion of lumbar vertebral column
• Multifidus
– Stabilizes adjacent vertebrae
– Maintains posture
10-50
Muscles of the Pelvic Floor
• Layers of muscles and fasciae that span pelvic
outlet
– Penetrated by anal canal, urethra, and vagina
• Perineum—diamond-shaped region between the
thighs
– Bordered by four bony landmarks
• Pubic symphysis anteriorly
• Coccyx posteriorly
• Ischial tuberosities laterally
– Urogenital triangle: anterior half of perineum
– Anal triangle: posterior half of perineum
10-51
Muscles of the Pelvic Floor
• Layers or compartments of the perineum
– Superficial perineal space
• Ischiocavernosus, bulbospongiosus
– Deep perineal space
• Deep transverse perineal, compressor urethrae
– Anal triangle
• External anal sphincter
– Pelvic diaphragm: deepest (most superior) layer
• Levator ani
10-52
Muscles of the Pelvic Floor
Figure 10.20a
• Superficial perineal space
– Ischiocavernosus—maintains erection
– Bulbospongiosus—aids in erection, expels remaining urine
10-53
Muscles of the Pelvic Floor
Figure 10.20b
• Deep perineal space
– Urogenital triangle—contains deep transverse perineal muscle
and compressor urethrae in females
• Anal triangle—external anal sphincter
10-54
Muscles of the Pelvic Floor
Figure 10.20c
• Pelvic diaphragm: deepest compartment of the perineum
– Levator ani: supports viscera and defecation
– Coccygeus muscle(s)
10-55
Hernias
• Hernia—any condition in which
the viscera protrudes through a
weak point in the muscular wall of
the abdominopelvic cavity
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Aponeurosis of external
abdominal oblique
muscle
• Inguinal hernia
Inguinal canal
– Most common type of hernia (rare
in women)
– Viscera enter inguinal canal or
even the scrotum
External inguinal ring
Herniated loop of
small intestine
Upper scrotum
• Hiatal hernia
– Stomach protrudes through
diaphragm into thorax
– Overweight people over 40
Figure 10.21
• Umbilical hernia
– Viscera protrude through the
navel
10-56
Muscles Acting on the Shoulder
and Upper Limb
• Expected Learning Outcomes
– Name and locate the muscles that act on the pectoral
girdle, shoulder, elbow, wrist, and hand.
– Relate the actions of these muscles to the joint
movements described in chapter 9.
– Describe the origin, insertion, and innervation of each
muscle.
10-57
Muscles Acting on the Shoulder
and Upper Limb
• Compartments—spaces where muscles are separated
by fibrous connective tissue sheets (fasciae)
– Each compartment contains one or more functionally
related muscles along with their nerve and blood supplies
• Muscles of upper limbs divided into anterior and
posterior compartments
• Intermuscular septa (thick fascia) separates
compartments
• Compartment syndrome—one of the muscles or blood
vessels in a compartment is injured
10-58
Compartment Syndrome
• If a blood vessel in a compartment is damaged, blood
and tissue fluid accumulate
• Fasciae enclose muscle compartments snugly and
prevent expansion
• Compartment syndrome—mounting pressure triggers a
sequence of degenerative events
– Blood flow to compartment is obstructed by pressure
– If ischemia (poor blood flow) persists for more than 2 to 4 hours,
nerves begin to die
– After 6 hours, muscles begin to die
• Nerves can regenerate after pressure relieved, but
muscle damage is permanent
• Myoglobin in urine indicates compartment syndrome
• Treatment: immobilization of limb and fasciotomy
(incision to relieve compartment pressure)
10-59
Muscles Acting on the Shoulder
and Upper Limb
• Upper limb is used for a broad range of powerful
and subtle actions
– Climbing, grasping, throwing, writing, playing musical
instruments, and manipulating small objects
• Muscles that act on the scapula
• Muscles that act on the humerus and shoulder
joint
• Muscles that act on the forearm and elbow joint
• Muscles that act on the wrist, hand, and fingers
10-60
Muscles Acting on the Shoulder
• A group of muscles originate on the axial
skeleton and insert on clavicle or scapula
• Scapula loosely attached to thoracic cage
– Capable of great movement
– Rotation, elevation, depression, protraction, retraction
• Clavicle braces the shoulder and moderates
movements
10-61
Muscles Acting on the Scapula
Figure 10.22
10-62
Muscles Acting on the Shoulder
• Anterior group of muscles of pectoral girdle
• Serratus anterior
• Pectoralis minor
– Ribs 3–5 to coracoid
process of scapula
– Draws scapula laterally
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subclavius
Pectoralis minor (cut)
– All ribs to medial
border of scapula
– Draws scapula laterally
and forward; prime
mover for reaching and
pushing
Pectoralis minor
Internal intercostals
Serratus anterior
External intercostals
Rectus abdominis (cut)
Rectus sheath
External abdominal
oblique (cut)
Internal abdominal
oblique (cut)
Internal abdominal
oblique
Posterior wall of rectus sheath
(rectus abdominis removed)
Inguinal ligament
Transverse abdominal (cut)
(b) Deep
Figure 10.15b
10-63
Muscles Acting on the Shoulder
• Posterior group of muscles
of pectoral girdle
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Superficial
Deep
• Four muscles of posterior group
– Trapezius: superficial
– Levator scapulae, Rhomboid
minor, and Rhomboid major:
deep
Semispinalis capitis
Sternocleidomastoid
Splenius capitis
Trapezius
Levator scapulae
Rhomboid minor
Rhomboid major
Supraspinatus
Infraspinatus
Teres minor
Deltoid
Teres major
Serratus anterior
Erector spinae
Serratus posterior
inferior
• Trapezius
– Stabilizes scapula and shoulder
– Elevates and depresses shoulder
apex
Latissimus
dorsi
External abdominal
oblique
External abdominal
oblique
Thoracolumbar
fascia
Internal abdominal
oblique
Gluteus medius
Gluteus minimus
Gluteus maximus
Lateral rotators
Figure 10.17
10-64
Muscles Acting on the Shoulder
(Continued from slide 170)
• Levator scapulae
– Elevates scapula
– Flexes neck laterally
• Rhomboid minor
– Retracts scapula and braces shoulder
• Rhomboid major
– Same as Rhomboid minor
10-65
Muscles Acting on the Shoulder
• Posterior scapular muscles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Superficial
Deep
Semispinalis capitis
Sternocleidomastoid
Splenius capitis
Trapezius
Levator scapulae
Rhomboid minor
Rhomboid major
Supraspinatus
Deltoid
Infraspinatus
Teres minor
Teres major
Erector spinae
Serratus anterior
Serratus posterior
inferior
Latissimus
dorsi
External abdominal
oblique
External abdominal
oblique
Thoracolumbar
fascia
Internal abdominal
oblique
Gluteus medius
Gluteus minimus
Gluteus maximus
Lateral rotators
Figure 10.17
10-66
Muscles Acting on the Arm
• Nine muscles cross the shoulder joint and insert on
humerus
• Two are axial muscles originating on axial skeleton
– Pectoralis major: flexes, adducts, and medially rotates humerus
– Latissimus dorsi: adducts and medially rotates humerus
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Supraspinatus
Deltoid
Clavicle
Spine of scapula
Sternum
Greater tubercle
of humerus
Infraspinatus
Humerus
Pectoralis major
Teres minor
Teres major
Triceps brachii:
Triceps brachii:
Lateral head
Long head
Coracobrachialis
Lateral head
Long head
Medial head
Biceps brachii
Latissimus dorsi
Brachialis
Brachioradialis
(a) Anterior view
Figure 10.23a
(b) Posterior view
Figure 10.23b
10-67
Anterior View of Cadaver Chest
Figure 10.24a
10-68
Back Muscles of Cadaver
Figure 10.24b
10-69
Muscles Acting on the Arm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Seven muscles with
scapular origin
Clavicle
Sternum
Deltoid
– Deltoid
• Rotates and abducts arm
• Intramuscular injection site
– Teres major
• Extension and medial
rotation of humerus
– Coracobrachialis
• Flexes and medially rotates
arm
Pectoralis major
Triceps brachii:
Lateral head
Long head
Medial head
Coracobrachialis
Biceps brachii
Brachialis
Brachioradialis
Figure 10.23a
(a) Anterior view
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Supraspinatus
Spine of scapula
Greater tubercle
of humerus
Infraspinatus
Humerus
Teres minor
– Remaining four form the
rotator cuff that reinforce
the shoulder joint
Teres major
Triceps brachii:
Lateral head
Long head
Latissimus dorsi
Figure 10.23b
10-70
(b) Posterior view
Muscles Acting on the Arm
• Rotator cuff muscles
• Tendons of the remaining four scapular muscles form the
rotator cuff
• Acronym “SITS muscles”
– Supraspinatus
– Infraspinatus
– Teres minor
– Subscapularis
• Tendons of these muscles merge with the joint capsule of
the shoulder as they cross it in route to the humerus
• Holds head of humerus into glenoid cavity
• Supraspinatus tendon easily damaged
10-71
Rotator Cuff Muscles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Anterior
Posterior
Clavicle
Rotator cuff (SITS)
muscles:
Acromion
Supraspinatus
Coracoid
process
Glenoid cavity
Infraspinatus
Teres minor
Subscapularis
Inferior angle
Figure 10.25
10-72
Muscles Acting on the Forearm
• Elbow and forearm capable of flexion, extension,
pronation, and supination
– Carried out by muscles in both brachium (arm) and
antebrachium (forearm)
• Muscles with bellies in the arm (brachium)
– Principal elbow flexors: anterior compartment
• Brachialis and biceps brachii
– Brachialis produces 50% more power than biceps brachii
– Brachialis is prime mover of elbow flexion
– Principal elbow extensor: posterior compartment
• Triceps brachii
– Prime mover of elbow extension
10-73
Muscles Acting on the Forearm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 10.23c
• Principal flexor
– Brachialis
Biceps brachii:
Long head
Short head
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• Synergistic
flexors
– Biceps brachii
– Brachioradialis
Clavicle
Sternum
Deltoid
Pectoralis major
Triceps brachii:
Lateral head
Long head
Medial head
Biceps brachii
Brachialis
Brachioradialis
Coracobrachialis
(c) Anterior view
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Supraspinatus
Spine of scapula
Greater tubercle
of humerus
Infraspinatus
Humerus
Teres minor
(a) Anterior view
Teres major
• Principal extensor
Figure 10.23a
Triceps brachii:
Lateral head
Long head
– Triceps brachii
Latissimus dorsi
Figure 10.23b
(b) Posterior view
10-74
Muscles Acting on the Forearm
• Muscles with bellies in the forearm
(antebrachium)
– Brachioradialis: flexes elbow
– Anconeus: extends elbow
– Pronator quadratus: prime mover in forearm
pronation
– Pronator teres: assists pronator quadratus in
pronation
– Supinator: supinates the forearm
10-75
Muscles Acting on the Forearm
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lateral epicondyle
Medial epicondyle
Lateral epicondyle
Medial epicondyle
Supinator
Supinator
Pronator teres
Pronator teres
Ulna
Ulna
Radius
Pronator quadratus
Radius
Pronator quadratus
Biceps
brachii
Biceps
brachii
Radius
Radius
Bursa
Supinator
Bursa
Supinator
Ulna
Ulna
(b) Muscle actions
in supination
(b) Muscle actions
in supination
(c) Pronation
(a) Supination
Figure 10.26a
• Supination
– Supinator muscle
– Palm facing anteriorly
or superiorly
Figure 10.26c
• Pronation
– Pronator quadratus and
pronator teres
– Palm faces posteriorly or
inferiorly
10-76
Muscles Acting on the Wrist and Hand
•
•
•
•
Anterior group
Extrinsic muscles of the forearm
Intrinsic muscles in the hand itself
Extrinsic muscle actions
–
–
–
–
Flexion and extension of wrist and digits
Radial and ulnar flexion
Finger abduction and adduction
Thumb opposition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Biceps brachii
Triceps brachii
Brachialis
Common flexor tendon
Common flexor
tendon
Pronator teres
Aponeurosis of biceps
brachii
Brachioradialis
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Anterior view
Supinator
Interosseous
membrane
Extensor carpi radialis
longus and brevis
Flexor
digitorum
superficialis
Flexor
digitorum
profundus
Flexor
pollicis longus
Flexor
pollicis
longus
Flexor digitorum
superficialis
Flexor
retinaculum
Palmar
aponeurosis
Figure 10.28a,b,c
(a) Superficial flexors
(b) Intermediate flexor
Flexor
digitorum
superficialis
tendons
Flexor
digitorum
superficialis
tendons
Flexor
digitorum
profundus
tendons
Flexor
digitorum
profundus
tendons
(c) Deep flexors
10-77
Muscles Acting on the Wrist and Hand
• Anterior (flexor) compartment—superficial
layer
–
–
–
–
Flexor carpi radialis
Flexor carpi ulnaris
Flexor digitorum superficialis
Palmaris longus
• Anterior (flexor) compartment—deep layer
– Flexor digitorum profundus
– Flexor pollicis longus
10-78
Cross Section of Upper Limb
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Deltoid
Pectoralis major
Biceps brachii:
Short head
Long head
(a)
Coracobrachialis
Humerus
Latissimus dorsi tendon
(b)
Teres major
Triceps brachii:
Lateral head
Long head
(c)
(a)
Anterior
Biceps brachii
Lateral
Medial
Brachialis
Posterior
Key
Anterior (flexor)
compartment, superficial
Anterior (flexor)
compartment, deep
(b)
Posterior (extensor)
compartment
Triceps brachii:
Medial head
Long head
Lateral head
Other muscles
Supinator
Pronator teres
Flexor carpi radialis
Palmaris longus
Radius
Flexor digitorum superficialis
Brachioradialis
Figure 10.27a,b,c
Extensor carpi radialis longus
Flexor pollicis longus
Flexor carpi ulnaris
Extensor carpi radialis brevis
Extensor digitorum
Flexor digitorum profundus
Ulna
Anconeus
Extensor digiti minimi
Extensor carpi ulnaris
(c)
10-79
Muscles Acting on the Wrist and Hand
•
•
•
•
Posterior group
Extension of wrist and fingers, adduct/abduct wrist
Extension and abduction of thumb (pollicis)
Brevis means “short,” ulnaris indicates “on ulna side of
forearm”
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Triceps brachii
Brachioradialis
Olecranon
Anconeus
Posterior view
Anconeus
Extensor carpi
radialis longus
Supinator
Extensor carpi
radialis brevis
Flexor carpi
ulnaris
Abductor pollicis
longus
Extensor digitorum
Extensor carpi
ulnaris
Abductor pollicis
longus
Extensor digiti
minimi
Extensor pollicis
brevis
Extensor pollicis
longus
Extensor pollicis
brevis
Extensor indicis
Extensor pollicis
longus
Tendon of
extensor indicis
Tendons of extensor
carpi radialis longus
and brevis
Tendons of extensor
digitorum
Figure 10.29a,b
(a) Superficial extensors
(b) Deep extensors
10-80
Muscles Acting on the Wrist and Hand
• Posterior (extensor) compartment—superficial layer
–
–
–
–
–
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
• Posterior (extensor) compartment—deep layer
–
–
–
–
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis
10-81
Carpal Tunnel Syndrome
• Flexor retinaculum—bracelet-like fibrous sheet,
passed under by flexor tendons crossing the wrist
• Carpal tunnel—tight space between the flexor
retinaculum and the carpal bones
– Flexor tendons passing through the tunnel are enclosed
in tendon sheaths
• Enable tendons to slide back and forth quite easily
10-82
Carpal Tunnel Syndrome
• Carpal tunnel syndrome—prolonged, repetitive
motions of wrist and fingers cause tissues in the
carpal tunnel to become inflamed, swollen, or fibrotic
– Puts pressure on median nerve of wrist that passes
through the carpal tunnel along with flexor tendons
– Tingling and muscular weakness in the palm and medial
side of the hand
– Pain may radiate to arm and shoulder
– Treatment: anti-inflammatory drugs, immobilization of the
wrist, and sometimes surgery to remove part or all of
flexor retinaculum
10-83
Carpal Tunnel Syndrome
Repetitive motions
cause inflammation
and pressure on
median nerve
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Tendon sheath
First dorsal
interosseous
Tendon of flexor
digitorum profundus
Adductor
pollicis
Tendon of flexor
digitorum superficialis
Lumbricals
Opponens
digiti minimi
Flexor pollicis
brevis
Flexor digiti
minimi brevis
Abductor pollicis
brevis
Abductor digiti
minimi
Opponens pollicis
Flexor retinaculum
Tendons of:
Flexor carpi ulnaris
Figure 10.31b
Tendon of flexor
pollicis longus
Flexor digitorum
superficialis
Palmaris longus
Tendons of:
Abductor pollicis
longus
Flexor carpi
radialis
Flexor pollicis
longus
(a) Palmar aspect, superficial
Figure 10.31a
10-84
Intrinsic Muscles of the Hand
• Thenar group—form thick, fleshy mass at base of
thumb
–
–
–
–
Adductor pollicis
Abductor pollicis brevis
Flexor pollicis brevis
Opponens pollicis
• Hypothenar group—fleshy base of the little finger
– Abductor digiti minimi
– Flexor digiti minimi brevis
– Opponens digiti minimi
• Midpalmar group—hollow of palm
– Dorsal interosseous muscles (4)
– Palmar interosseous muscles (3)
– Lumbricals (4 muscles)
10-85
Muscles Acting on the Hip
and Lower Limb
• Expected Learning Outcomes
– Name and locate the muscles that act on the hip,
knee, ankle, and toe joints.
– Relate the actions of these muscles to the joint
movements described in chapter 9.
– Describe the origin, insertion, and innervation of each
muscle.
10-86
Muscles Acting on the Hip
and Lower Limb
• Body’s largest muscles found in lower limb
• Less for precision, more for strength needed
to stand, maintain balance, walk, and run
• Several cross and act on two or more joints
• Leg—the part of the limb between the knee and
ankle
• Foot—includes tarsal region (ankle),
metatarsal region, and the toes
10-87
Muscles Acting on the Hip and Femur
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Anterior muscles of the hip
– Iliacus
• Flexes thigh at hip
• Iliacus portion arises from iliac
crest and fossa
– Psoas major
• Flexes thigh at hip
• Arises from lumbar vertebrae
Iliopsoas:
Iliacus
Psoas
major
Piriformis
Pectineus
Obturator
externus
Adductor
magnus
Adductor
brevis
Adductor
longus
Gracilis
– They share a common tendon
on the femur
Insertion of
gracilis on
tibia
Figure 10.32
10-88
Muscles Acting on the Hip and Femur
• Lateral and posterior
muscles of the hip
– Tensor fasciae latae
• Extends knee, laterally
rotates knee
– Gluteus maximus
• Forms mass of the buttock
• Prime hip extensor
• Provides most of lift when
you climb stairs
– Gluteus medius and
minimus
• Abduct and medially rotate
thigh
Figure 10.33
10-89
Muscles Acting on the Hip and
Femur
• Posterior group
• Lateral rotators—six muscles inferior to
gluteus minimus
• Deep to the two other gluteal muscles
–
–
–
–
–
–
Gemellus superior
Gemellus inferior
Obturator externus
Obturator internus
Piriformis
Quadratus femoris
10-90
Muscles Acting on the Hip and Femur
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Medial (adductor)
compartment of thigh
• Five muscles act as
primary adductors of the
thigh
–
–
–
–
–
Adductor brevis
Adductor longus
Adductor magnus
Gracilis
Pectineus
Iliopsoas:
Iliacus
Psoas
major
Piriformis
Pectineus
Obturator
externus
Adductor
magnus
Adductor
brevis
Adductor
longus
Gracilis
Insertion of
gracilis on
tibia
Figure 10.32
10-91
Muscles Acting on the Knee and Leg
• Anterior (extensor) compartment of the thigh
– Contains large quadriceps femoris muscle
• Prime mover of knee extension
• Most powerful muscle in the body
• Has four heads—rectus femoris, vastus lateralis,
vastus medialis, and vastus intermedius
–
–
–
–
All converge on single quadriceps (patellar) tendon
Extends to patella
Then continues as patellar ligament
Inserts on tibial tuberosity
– Sartorius: longest muscle in the body
• “Tailor’s muscle”
10-92
Anterior Thigh Cadaver Muscles
Figure 10.34
10-93
Muscles Acting on the Knee and Leg
Figure 10.35a,b
10-94
Muscles Acting on the Knee and Leg
• Posterior (flexor)
compartment of the thigh
– Contains hamstring muscles
– From lateral to medial:
Biceps femoris
Semitendinosus
Semimembranosus
Figure 10.33
10-95
Muscles Acting on the Foot
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(a)
Posterior
Lateral
Medial
Figure 10.40b
(b)
Anterior
Gastrocnemius
(lateral head)
Key b
Anterior (extensor)
compartment
Lateral (fibular) compartment
Posterior (flexor)
compartment, superficial
Posterior (flexor
compartment, deep)
Fibula
Fibularis longus
Fibularis brevis
Extensor hallucis longus
Gastrocnemius
(medial head)
Soleus
Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior
Tibia
Extensor digitorum longus
(b)
Tibialis anterior
• Crural muscles, acting on the foot, are separated
into three compartments
– Anterior compartment (red)
– Fibular (lateral) compartment (green)
– Posterior compartments (superficial = pink) (deep = purple)
10-96
Muscles Acting on the Foot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Patella
Patellar
ligament
Tibia
Gastrocnemius
Fibularis
longus
Soleus
Fibularis
brevis
Extensor
digitorum longus
Tibialis
anterior
Tibialis
anterior
Extensor
hallucis
longus
Extensor retinacula
Fibularis
tertius
Extensor
hallucis
brevis
Extensor
digitorum
brevis
(a)
(b)
Extensor
digitorum
longus
Figure 10.38a–d
(c)
(d)
• Anterior (extensor) compartment of the leg
– Dorsiflex the ankle
– Prevent toes from scuffing ground when walking
– Fibularis (peroneus) tertius
– Extensor digitorum longus
– Extensor hallucis longus
– Tibialis anterior
10-97
Muscles Acting on the Foot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Plantaris
Popliteus
Gastrocnemius:
Medial head
Lateral head
Heads of
gastrocnemius
(cut)
Fibularis
longus
Soleus
Tendon of
plantaris
Tendon of
gastrocnemius
Flexor
digitorum
longus
Gastrocnemius
(cut)
Fibularis
longus
Fibularis
brevis
Flexor
hallucis
longus
Figure 10.38a,b
Calcaneal tendon
(a)
Calcaneus
(b)
• Posterior compartment—three muscles of the superficial group
– Gastrocnemius: plantar flexes foot, flexes knee
– Soleus: plantar flexes foot
– Plantaris: weak synergist of triceps surae
• Triceps surae—collective name for gastrocnemius and soleus
– Inserts on calcaneus by way of the calcaneal (Achilles) tendon
– Strongest tendon in the body
10-98
Muscles Acting on the Foot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Tibialis
posterior
Flexor
digitorum
longus
Plantaris (cut)
Gastrocne
-mius (cut)
Popliteus
Soleus (cut)
Fibula
(b)
(c)
Tibialis
posterior
Fibularis
longus
Flexor digitorum
longus
Popliteus
Flexor hallucis
longus
Fibularis
brevis
Flexor
hallucis
longus
Plantar surface
of the foot
Calcaneal tendon
(cut)
(a)
Calcaneus
Figure 10.39
(d)
• Posterior compartment—four muscles in the deep group
–
–
–
–
Flexor digitorum longus: flexes phalanges
Flexor hallucis longus: flexes great toe
Tibialis posterior: inverts foot
Popliteus: acts on knee
10-99
Muscles Acting on the Foot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Lateral (fibular)
compartment—two
muscles
– Fibularis longus
– Fibularis brevis
Plantaris (cut)
Gastrocnemius (cut)
Popliteus
Soleus (cut)
Fibula
Tibialis
posterior
• Both plantar flex and
evert the foot
Fibularis
longus
Flexor digitorum
longus
Flexor hallucis
longus
Fibularis
brevis
Calcaneal tendon
(cut)
• Provide lift and
forward thrust
Figure 10.39a
Calcaneus
(a)
10-100
Intrinsic Muscles of Foot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• One dorsal
muscle
– Extensor
digitorum
brevis extends
toes
Lumbricals
Flexor hallucis
longus tendon
Flexor digitorum
longus tendon
Abductor hallucis
(cut)
Flexor digiti
minimi brevis
Abductor hallucis
Abductor digiti
minimi
Flexor digitorum
brevis
Quadratus plantae
Plantar aponeurosis
(cut)
Flexor digitorum
brevis (cut)
Calcaneus
(a) Layer 1, plantar view
• Four ventral
muscle layers
– Support arches
– Abduct and
adduct the toes
– Flex the toes
(b) Layer 2, plantar view
Figure 10.41a–e
Adductor hallucis
Plantar
Flexor hallucis brevis interosseous
Flexor digiti
minimi brevis
Flexor hallucis
longus tendon (cut)
Dorsal
interosseous
Abductor hallucis (cut)
Quadratus plantae
(cut)
Flexor digitorum
longus tendon (cut)
(c) Layer 3, plantar view
Dorsal
view
(d) Layer 4, plantar view
(e) Layer 4, dorsal view
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Common Athletic Injuries
• Muscles and tendons are vulnerable to
sudden and intense stress
• Proper conditioning and warm-up needed
• Common injuries include:
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Compartment syndrome
Shin splints
Pulled hamstrings
Tennis elbow
Pulled groin
Rotator cuff injury
• Treat with rest, ice, compression, and elevation
• “No pain, no gain” is a dangerous misconception
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