THE MUSCULAR SYSTEM
INTERACTIONS OF SKELETAL
MUSCLES IN THE BODY
•
Muscles only pull; they are not capable of pushing
– Generally as a muscle shortens, its insertion (attachment on the movable bone)
moves toward its origin (its fixed or immovable point of attachment)
•
Muscles can be classified into four functional groups:
– 1.Prime Movers:
• The muscle that provides the major force for the specific movement is called the
prime mover or the agonist, of that movement
– The biceps brachii muscle, which fleshes out the anterior arm (and inserts on the radius), is a
prime mover of elbow flexion
– 2.Antagonists:
• Muscles that oppose or reverse a particular movement
• When a prime mover is active, the antagonist muscles are often stretched and may be
relaxed
• Can also help to regulate the action of a prime mover by contracting to provide some
resistance, thus helping to prevent overshoot or to slow or stop the movement
• Prime mover and its antagonist are located on opposite sides of the joint across
which they act
• Antagonists can also be prime movers in their own right
– Example: flexion of the forearm by the biceps brachii muscle of the arm is antagonized by the
triceps brachii, the prime mover for extending the forearm
INTERACTIONS OF SKELETAL
MUSCLES IN THE BODY
• 3.Synergists:
– Help the prime movers by:
• Adding a little extra force to the same movement
• Or reducing undesirable or unnecessary movements that
might occur as the prime mover contracts
– When a muscle crosses two or more joints, its contraction
causes movement at all of the spanned joints unless other
muscles act as joint stabilizers
» Example: the finger flexor muscles cross both the wrist
and the phalangeal joints, but you can make a fist without
bending your wrist because synergistic muscles stabilize
the wrist
– As some flexors act, undesirable rotation movements occur
» Synergists can prevent this, allowing all of the prime
mover’s force to be exerted in the desired direction
INTERACTIONS OF SKELETAL
MUSCLES IN THE BODY
• 4.Fixators: when synergists immobilize
a bone, or a muscle’s origin, they are
more specifically called fixators
– Examples:
• Scapula is held to the axial skeleton only by
muscles and is quite freely movable
– The fixator muscles that run from the axial skeleton to the
scapula can immobilize the scapula so that only the
desired movements occur at the mobile shoulder joint
• Muscles that help to maintain upright posture
INTERACTIONS OF SKELETAL
MUSCLES IN THE BODY
• Although prime movers seem to get all the
credit for causing certain movements,
antagonistic and synergistic muscles are
also important in producing smooth,
coordinated, and precise movements
• A muscle may act as a prime mover in
one movement, an antagonist for
another movement, a synergist for a
third movement, and so on
NAMING SKELETAL MUSCLES
• 1. Location of the muscle: Some muscle names indicate the bone or
body region with which the muscle is associated
– Example:
• Temporalis muscle overlies the temporal bone
• Intercostal muscles run between the ribs
• 2. Shape of the muscle: Some muscles are named for their shape
– Example:
• Deltoid muscle is roughly triangular
• Together the right and left trapezius muscles form a trapezoid
• 3. Relative size of the muscle: Terms such as maximus (largest),
minimus (smallest), longus (long), and brevis (short) are often used
in muscle names to indicate relative size of the muscle
– Example:
• Gluteus maximus
• Gluteus minimus
NAMING SKELETAL MUSCLES
• 4. Direction of muscle fibers: The names of
some muscles indicate the direction in which
their fibers (and fascicles) run in reference to
some imaginary line, usually the midline of the
body or the longitudinal axis of a limb bone
– Examples:
• Rectus (straight): fibers run parallel to that imaginary line
(axis)
– Rectus femoris: straight muscle of the thigh, or femur)
• Transversus (right angle): muscle fibers run at right angles
– Transversus abdominis: transverse muscle of the abdomen
• Oblique (oblique angle): muscle fibers run at oblique angles
– External oblique: oblique muscle of the abdomen
NAMING SKELETAL MUSCLES
• 5. Number of origins: The number of
origins a muscle has may be indicated by
the word biceps, triceps, or quadriceps
– Example:
• Biceps brachii: muscle of the arm has two origins
(heads)
NAMING SKELETAL MUSCLES
• 6. Location of the attachments: Some
muscles are named according to the
location of their origin and insertion
– Origin is always named first
• Example:
– Sternocleidomastoid: muscle of the neck
» Has a dual origin on the sternum (sterno) and
clavicle (cleido), and it inserts on the mastoid
process of the temporal bone
NAMING SKELETAL MUSCLES
• 7. Action: A muscle may be named for its action
by using such words as flexor (flex), extensor
(extend), adductor (brought toward), or supinate
(bend backward) in its name
– Example:
• Adductor longus: located in the medial thigh
– Brings about thigh adduction (toward the main axis of the body
or a limb)
• Supinator muscle:
– Supinates the forearm:
» Turn the forearm or hand so that the palm faces upward
– Supinates the leg and foot:
» To rotate the foot and leg outward
NAMING SKELETAL MUSCLES
• Several criteria are combined in the
naming of some muscles
– Example: extensor carpi radialis longus
– Action of the muscle: the muscles action (extensor)
– Location of attachment: joint it acts on (carpi = wrist)
– Location of muscle: lies close to the radius of the
forearm (radialis)
– Relative size of muscle: relative to other wrist extensor
muscles (longus)
• Unfortunately, not all muscle names are this
descriptive
MUSCLE MECHANICS:
IMPORTANCE OF FASCICLE ARRANGEMENT
AND LEVERAGE
• In skeletal muscles the common
arrangement of the fascicles varies,
resulting in muscles with different shapes
and functional capabilities
Arrangement of Fascicles
• Fascicle: bundle of
nerve or muscle fibers
(cells) bound together
by connective tissue
• All skeletal muscles
consist of fascicles, but
fascicle arrangement
vary, resulting in
muscles with different
shapes and functional
capabilities
SKELETAL MUSCLE
Arrangement of Fascicles
• (a): Circular pattern:
– Fascicles arranged in
concentric rings
– Muscles with this
arrangement surround
external openings, which
they close by contracting
– General term for these
muscles is sphincters
(squeezers)
– Examples:
• Orbicularis muscles
surrounding the eyes
(Orbicularis oculi) and
the mouth (Orbicularis
oris)
Arrangement of Fascicles
• (b): Convergent pattern:
– Muscle has a broad
origin, and its fascicles
converge toward a single
tendon of insertion
– Such a muscle is triangular
or fan shaped like the
pectoralis major muscle
of the anterior thorax
Arrangement of Fascicles
• (c)(f): Parallel pattern:
– The long axes of the
fascicles run parallel to
the long axis of the
muscle
– Such muscles are either:
• straplike (c: parallel)
• spindle (f: fusiform)
– shaped with an
expanded belly
(midsection)
– Examples:
• Sartorius of thigh (c)
• Biceps brachii muscle of
the arm (f)
Arrangement of Fascicles
•
(d)(e)(g): Pennate pattern:
– In a pennate (feather) pattern of
arrangement the fascicles are short and
attach obliquely to a central tendon that
runs the length of the muscle
– Types:
• Unipennate: d
– Fascicles insert into only one
side of the tendon
– Example: extensor digitorum
muscle of the leg
• Bipennate: g
– Fascicles insert into the tendon
from opposite sides (muscle
grains resemble a feather)
– Example: rectus femoris muscle
of the thigh
• Multipennate: e
– Arrangement looks like many
feathers situated side by side,
with all their quills inserted into
one large tendon
– Example: deltoid muscle, which
forms the roundness of the
shoulder
FASCICLE ARRANGEMENT
TO
MUSCLE STRUCTURE
MUSCLE MECHANICS:
IMPORTANCE OF FASCICLE ARRANGEMENT
AND LEVERAGE
•
The operation of most skeletal
muscles involves the use of
leverage and lever systems,
partnerships between the
muscular and skeletal systems
– A lever is a rigid bar that moves
on a fixed point, or a fulcrum,
when a force is applied to it
– The applied force, or effort is used
to move a resistance or load
– In your body, your joints act as
the fulcrums, the bones as the
levers, and the muscle
contraction as the effort (force)
• Load (resistance) is the bone
itself, along with overlying
tissues and anything else you
are trying to move with that
lever
Lever Systems
• A lever allows a given effort
(force) to lift a heavier load
(resistance), or to move a
load (resistance) farther or
faster, than it otherwise
could
– (a):First-Class: the load is
close to the fulcrum and the
effort is applied far from the
fulcrum
• A small effort exerted over a
relatively large distance can
be used to move a large load
over a small distance
• Such a lever is said to
operate at a mechanical
advantage and is
commonly called a power
lever
Lever Systems
• (b): Third-Class:
– Load is far from the
fulcrum and the effort is
applied near the fulcrum,
the force exerted by the
muscle must be greater
than the load moved or
supported
– This lever system operates
at a mechanical
disadvantage and is a
speed lever
– These levers are useful
because they provide
rapid contractions with a
wide range of motion
MUSCLE LEVERAGE
Lever Systems
• All levers follow the same basic principle:
– Effort farther than load from fulcrum = mechanical
advantage
– Effort nearer than load to fulcrum = mechanical
disadvantage
• Lever systems that operate at a mechanical
disadvantage (speed levers), force is lost but
speed and range of movement are gained,
and this can be a distinct benefit
• Lever systems that operate at a mechanical
advantage (power levers) are slower, more
stable, and used where strength is a priority
Lever Systems
• There are three
types of levers:
– First-class
– Second-class
– Third-class
Lever Systems
First-Class Levers
• (a): Effort is applied at one
end of the lever and the load
is at the other, with the
fulcrum somewhere between
• Examples:
– Seesaws
– Scissors
– Lift your head off your chest
• Some operate at a
mechanical advantage
• Others operate at a
mechanical disadvantage
– Action of the triceps muscle in
extending the forearm against
resistance (pushing)
Lever Systems
Second-Class Levers
•
•
•
•
(b): Effort is applied at one end
of the lever and the fulcrum is
located at the other, with the
load between them
All second-class levers in the body
work at a mechanical advantage
because the muscle insertion
(effort) is always farther from the
fulcrum than is the load to be
moved
Levers of strength, but speed
and range are sacrificed for that
strength
Examples:
– Wheelbarrow
– Uncommon in the human body
• Best example is the act of
standing on your toes
Lever Systems
Third-Class Levers
•
•
•
(c): Effort is applied between
the load and the fulcrum
Operate with great speed and
always at a mechanical
disadvantage
Most skeletal muscles of the
body
– Tend to be thicker and more
powerful
– Permits a muscle to be inserted
very close to the joint across
which movement occurs
• Allows rapid, extensive
movements with relatively little
shortening of the muscle
•
Examples:
– Tweezers (forceps)
– biceps
MUSCLE LEVERAGE
Skeletal Muscles
• Over 600
– Book only list approximately 125 pairs of them
ANTERIOR SUPERFICIAL
MUSCLES
DIAGRAMMATIC VIEW
OF
ANTERIOR MUSCLES
POSTERIOR VIEW
OF
SUPERFICIAL MUSCLES
DIAGRAMMATIC VIEW
OF
POSTERIOR MUSCLES
Facial Muscles
•
Muscles of the Head: Facial
Expression
– Muscles of the scalp include
the epicranius consisting of
the frontalis and the
occipitalis
– Muscles of the face include
corrugator supercilii,
orbicularis oculi,
zygomaticus, risorius, levator
labii superioris, depressor labii
inferioris, depressor anguli
oris, orbicularis oris,
mentalis, buccinator, and
platysma
MAJOR SKELETAL MUSCLES
OF
THE FACE
•
Frontalis:cranial (facial nerve)
VII
– Raises the eyebrows (as in
surprise)
– Wrinkles forehead skin
horixzontally
– Cranial nerve VII
•
Orbicularis oculi:cranial (facial
nerve) VII
– Protects eyes from intense light
and injury
– Produces blinking, squinting
– Draws the eyebrows inferiorly
•
Orbicularis oris:cranial (facial
nerve) VII
– Closes lips
– Purses (pucker) and protrudes
(stick out) lips
– Kissing and whistling muscle
HEAD MUSCLES
Muscles of the Head
• Mastication and Tongue
Movement:
– Muscles of mastication
include the masseter,
temporalis, medial
pterygoid, lateral pterygoid,
and the buccinator
– Muscles promoting tongue
movement are the
genioglossus,
hypoglossus, and the
styloglossus
Mastication Muscles
• Masseter:Temporalis:cranial
(trigeminal) nerve V
– Prime mover of jaw closure
– Elevates mandible
• Temporalis:cranial (trigeminal)
nerve V
– Closes jaw
– Elevates and retracts
mandible
• Buccinator:cranial (facial)
nerve VII
– Trampoline-like action
– Keeps food between grinding
surfaces of teeth during
chewing
Mastication Muscles
HEAD MUSCLES
Mastication Muscles
Tongue Muscles
• Genioglossus:cranial
(hypoglossal) nerve
XII
– Primarily protrudes
tongue, but in concert
with other extrinsic
muscles to retract
tongue
TONGUE MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles of the Anterior
Neck and Throat:
Swallowing
– Suprahyoid muscles
include digastric,
stylohyoid, mylohyoid, and
geniohyoid
– Infrahyoid muscles include
sternohyoid, sternothyroid,
omohyoid, thyrohyoid, and
the pharyngeal
constrictor muscles
(superior, middle, and
inferior)
Neck and Throat Muscles
• Mylohyoid:cranial
(trigeminal) nerve V
– Elevates hyoid bone
and floor of mouth
– Enables the tongue to
exert backward and
upward pressure that
forces food bolus into
pharynx
Neck and Throat Muscles
• Pharyngeal
constrictor muscles
(superior, middle, and
inferior):cranial
(vagus) nerve X
– Working as a group
and in sequence, all
constrict pharynx
during swallowing
– Propels food bolus
to esophagus
• peristalsis
NECK MUSCLES
NECK MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles of the Neck and Vertebral
Column: Head and Trunk Movement
– Anterolateral neck muscles include the
sternocleidomastoid, and scalenes (anterior,
middle, and posterior)
– Intrinsic muscles of the back include splenius
capitis, erector spinae or sacrospinalis,
iliocostals, longissimus, spinalis, semispinalis,
and the quadratus lumborum
Neck Muscles
• Sternocleidomastoid: cranial
(accessory) nerve XI and
branches of cervical nerves 24:
– Prime mover of head
flexion
– Neck flexion
– Head movement side-toside
NECK AND VERTEBRAL
COLUMN MUSCLES
NECK AND VERTEBRAL
COLUMN MUSCLES
NECK AND VERTEBRAL
COLUMN MUSCLES
Neck and Vertebral Column Muscles
• Longissimus:
thoracis, cervicis, and
capitis: spinal nerves:
– Capitis: extends head
and turns face side to
side
– Thoracis and
cervicis: extend
vertabral column side
to side
NECK AND VERTEBRAL
COLUMN MUSCLES
Thorax and Abdominal Muscles
• Muscles of the Thorax: Breathing
– Muscles of the thorax include the external
intercostals, internal intercostals, and the
diaphragm
• Muscles of the Abdominal Wall: Trunk
Movement and Compression of Abdominal
Viscera
– Muscles of the anterolateral abdominal wall
include the rectus abdominis, external
oblique, and the transversus abdominis
Thorax Muscles
• External intercostals:
intercostal nerves:
– Elevate rib cage
– Aids in inspiration
• Internal intercostals:
intercostal nerves:
– Depress rib cage
– Aids in expiration
• Diaphragm:cervical
(phrenic) nerve (C3-C5)
– Breathing
RESPIRATORY MUSCLES
RESPIRATORY MUSCLES
Abdominal Muscles
• Rectus abdominis:
Intercostal (thoracic)
nerves:
– Flex and rotate lumbar
region
• External oblique:
Intercostal (thoracic)
nerves:
– Compression of abdominal
wall
• Transversus abdominis:
Intercostal (thoracic)
nerves:
– Compression of abdominal
wall
ABDOMINAL MUSCLES
ABDOMINAL MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles of the Pelvic Floor and Perineum:
Support of Abdominopelvic Organs:
– Muscles of the pelvic diaphragm include the
levator ani and the coccygeus
– Muscles of the urogenital diaphragm include
the deep transverse perineus and the
sphincter urethrae
– Muscles of the superficial space include the
ischiocavernosus, bulbospongiosus, and
the superficial transverse perineus
PELVIC FLOOR
AND
PERINEUM MUSCLES
Pelvic Floor Muscles
• Ischiocavernosus:
pudendal (sacral) nerve:
– Retards venous drainage
and maintains erection of
penis or clitoris
• Bulbospongiosus:
pudendal (sacral) nerve:
– Empties male urethra
– Assist in erection of
penis in males and of
clitoris in females
PELVIC FLOOR
AND
PERINEUM MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Superficial Muscles of the Anterior and
Posterior Thorax: Movements of the
Scapula
– Muscles of the anterior thorax include the
pectoralis minor, serratus anterior, and the
subclavius
– Muscles of the posterior thorax include the
trapezius, levator scapulae, and the
rhomboids (major and minor)
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles Crossing the Shoulder Joint:
Movement of the Arm
– Muscles moving the arm include the
pectoralis major, latissimus dorsi, deltoid,
subscapularis, supraspinatous,
infraspinatous, teres minor, teres major, and
the coracobrachialis
Thorax Muscles
•
Deltoid: cervical nerves:
– Prime mover of arm abduction
– Antagonists of pectoralis major
and latissimus dorsi
•
Pectoralis major: cervical and
thoracic nerves:
– Prime mover of arm flexion
– Adduction
•
Trapezius: cervical nerves:
– Stabilizes, raises, retracts, and
rotates scapula
•
Latissimus dorsi: cervical nerves
– Prime mover of arm extension
– Powerful arm adductor
• Striking a blow
• Swimming
• Rowing
THORAX MUSCLES
SHOULDER MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles crossing the Elbow Joint: Flexion
and Extension of the Forearm
– Posterior muscles include the triceps
brachii, and the anconeus
– Anterior muscles include the biceps
brachii, brachialis, and the brachioradialis
SHOULDER MUSCLES
• Triceps brachii: cervical
nerves:
– Powerful forearm extensor
• Biceps brachii: cervical
nerves:
– Flexes elbow joint and
supinates forearm
• Brachialis: musculocutaneous
nerve:
– Major forearm flexor
• Lifts ulna as biceps lifts the
radius
• Brachioradialis: radial nerve:
– Synergist in forearm flexion
SHOULDER MUSCLES
SHOULDER MUSCLES
Forearm Muscles
• Flexor carpi radialis:
median nerve:
– Powerful flexor of wrist
– Abducts hand
• Flexor carpi ulnaris:
ulnar nerve:
– Powerful flexor of wrist
– Adducts hand
ANTERIOR ARM MUSCLES
Forearm Muscles
• Extensor carpi
radialis brevis: radial
nerve:
– Extends and abducts
wrist
• Extensor digitorum:
branch of radial
nerve:
– Prime mover of finger
extension
– Extends wrist
POSTERIOR ARM MUSCLES
ARM MUSCLES
ARM MUSCLE ACTIONS
ARM MUSCLE ACTIONS
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles of the Forearm: Movements of the Wrist,
Hand, and Fingers
– Anterior superficial muscles include the pronator teres, flexor
carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor
digitorum superficialis
– Anterior deep muscles include the flexor pollicis longus, flexor
digitorum profundus, and the pronator quadratus
– Posterior superficial muscles include the brachioradialis,
extensor carpi radialis longus, extensor carpi radialis brevis,
extensor digitorum, and the extensor carpi ulnaris
– Posterior deep muscles include the supinator, abductor pollicis
longus, extensor pollicis longus, and the extensor pollicis brevis
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Intrinsic muscles of the Hand: Fine
Movements of the Fingers
– Thenar muscles in ball of thumb include the
abductor pollicis brevis, flexor pollicis brevis,
opponnens pollicis, and the adductor pollicis
– Hypothenar muscles in ball of little finger
include the abductor digiti minimi, flexor digiti
minimi brevis, and the opponens digiti minimi
– Midpalmar muscles include the lumbricals,
palmar interossei, and the dorsal interossei
Hand Muscles
• Abductor pollicis
brevis: median nerve
(cervical.thoracic)
– Abducts thumb
• Flexor digiti minimi
brevis: ulnar nerve:
– Flexes little finger
HAND MUSCLES
HAND MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles Crossing the Hip and Knee Joints: Movements of the Thigh
and Leg
– Anteromedial muscles include the iliopsoas, which is composed of the
iliacus, the psoas major, and the sartorius
– Muscles of the medial compartment of the thigh include the adductor
group, which is made up of the adductor magnus, adductor longus and
the adductor brevis, the pectineus, and the gracilis
– Muscles of the anterior compartment of the thigh include the quadriceps
femoris group, which is made up of the rectus femoris, vastus lateralis,
vastus medialis and vastus intermedius, and the tensor fasciae latae
– Posterior Muscles: gluteal muscles (origin on pelvis) include the gluteus
maximus, gluteus medius, and the gluteus minimus
– Lateral rotators include the piriformis, obturator externus, obturator
internus, gemellus, and the quadratus femoris
– Muscles of the posterior compartment of the thigh include the hamstring
group, which consist of the biceps femoris, semitendinosus, and the
semimembranosus
Thigh Muscles
• Adductor longus:
obturator nerve:
– Adducts, flexes, and
medially rotates thigh
• Gracilis: obturator nerve:
– Adducts thigh, flexes, and
medially rotates thigh,
especially during walking
• Quadriceps femoris:
– Rectus femoris: femoral
nerve:
• Extends knee and flexes
thigh at hip
ANTERIOR THIGH MUSCLES
ANTERIOR THIGH MUSCLES
Hip Muscles
• Gluteus maximus:
inferior gluteal nerve:
– Major extensor of thigh
– Complex, powerful, and
most effective when thigh
is flexed and force is
necessary, as in rising from
a forward flexed position
and in thrusting the thigh
posteriorly in climbing
stairs and running
– Inactive during standing
POSTERIOR THIGH MUSCLES
• Hamstrings: sciatic
nerve
• Biceps femoris
• Semitendinosus
• Semimembranosus
– Extends thigh and
flexes knee
POSTERIOR THIGH MUSCLES
POSTERIOR THIGH MUSCLES
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Muscles of the Leg: Movements of the Ankle and
Toes
– Muscles of the anterior compartment include the tibialis anterior,
extensor digitorum longus, fibularis (peroneus) tertius, and the
extensor hallucis longus
– Muscles of the lateral compartment include the fibularis
(peroneus) longus and the fibularis (peroneus) brevis
– Superficial muscles of the posterior compartment include the
triceps surae, which is composed of the gastrocnemius and the
soleus, and the plantaris
– Deep muscles of the posterior compartment include the
popliteus, flexor digitorum longus, flexor hallucis longus, and the
tibialis posterior
ANTERIOR LEG MUSCLES
• Tibialis anterior: fibular
nerve (lumbar):
– Prime mover of dorsiflexion
– Inverts foot
– Assists in supporting
medial longitudinal arch of
foot
• Fibularis longus: fibular
nerve (lumbar):
– Plantar flexes and everts
foot
– May help keep foot flat on
ground
ANTERIOR LEG MUSCLES
ANTERIOR LEG MUSCLES
LATERAL LEG MUSCLES
LATERAL LEG MUSCLES
POSTERIOR LEG MUSCLES
• Gastrocnemius: tibial
nerve (sacral):
– Plantar flexes foot when
knee is extended
– Since it also crosses knee
joint, it can flex knee when
foot is dorsiflexed
• Soleus: tibial nerve
(sacral):
– Plantar flexes foot
– Important locomotor and
postural muscle during
walking, running, and
dancing
POSTERIOR LEG MUSCLES
POSTERIOR LEG MUSCLES
POSTERIOR LEG MUSCLES
POSTERIOR LEG MUSCLES
LEG MUSCLE ACTIONS
LEG MUSCLE ACTIONS
MAJOR SKELETAL MUSCLES
OF
THE BODY
• Intrinsic Muscles of the Foot: Toe Movement and
Arch Support
– The muscle found on the dorsum of the foot is the extensor
digitorum brevis
– Muscles on the sole of the foot found in the first layer are the
flexor digitorum brevis, abductor hallucis, and the abductor digiti
minimi
– Muscles on the sole of the foot found in the second layer are the
flexor accessorius (quadratus plantae) and the lumbricals
– Muscles of the sole of the foot found in the third layer include the
flexor hallicis brevis, adductor hallucis, and the flexor digiti
minimi brevis
– Muscles of the sole of the foot found in the fourth layer include
the plantar and the dorsal interossei
Foot Muscles
Dorsum
• Extensor digitorum
brevis: fibular nerve
(sacral):
– Helps extend toes
Foot Muscles
Sole
• Flexor digitorum
brevis: medial plantar
nerve (sacral):
– Helps flex toes
FOOT MUSCLES
FOOT MUSCLES
FOOT MUSCLES