The Muscular System
Muscle Attachment Sites
 Muscle exerts force on tendons, which in
turn pull on bones or other structures.
 When a muscle contracts, it pulls one of the
articulating bones toward the other.
Muscle Attachment Sites:
Origin & Insertion
 Origin – the site of a muscle’s attachment to
the more stationary bone.
 Insertion – the site of a muscle’s attachment
to the more movable bone.
 Often, the origin is proximal to the insertion.
 Belly – the fleshy part of the muscle between
the tendons of the origin and insertion.
Tenosynovitis
 Commonly known as tendinitis.
 Painful inflammation of the tendons, tendon
sheaths, and synovial membranes of the
joints.
 Trauma, strain, excessive exercise, chronic,
repetitive motions can all cause
tenosynovitis.
Lever Systems & Leverage
 A lever is a rigid structure that can move
around a fixed point called a fulcrum.
 Two forces act upon a lever:
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Effort – causes movement.
Load (resistance) – opposes movement.
Lever Systems & Leverage
 Levers produce trade-offs between effort and
the speed and range of motion.
 Mechanical advantage (leverage) – a smaller
effort can move a heavier load – the effort
must move a greater distance.
 Mechanical disadvantage – a larger effort
moves a lighter load – the effort must move a
shorter distance and slower than the load.
Types of Levers
 First-class levers.
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The fulcrum is between the effort and the load.
Scissors and seesaws are examples.
It can produce either a mechanical advantage or
disadvantage depending upon whether the effort or load
is placed closer to the fulcrum.
If an effort is placed farther from the fulcrum than the
load, a heavy load can be moved, but not fast or far.
If an effort is placed closer to the fulcrum than the load,
only a lighter load can be moved, but it moves far and
fast.
Raising the head at the atlanto-occipital joint.
Types of Levers
 Second-class levers.
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The load is between the fulcrum and the effort.
An example is a wheelbarrow.
Always produces a mechanical advantage
because the load is always closer to the fulcrum
than the effort.
None present in the human body.
Types of Levers
 Third-class levers.
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The effort is between the fulcrum and the load.
An example is a forceps.
Always produces a mechanical disadvantage
because the effort is always closer to the fulcrum
than the load.
This arrangement favors speed and range of
motion over force.
Effects of Fascicle
Arrangement
 Within a fascicle, all muscles are parallel to one
another.
 The fascicles may form patterns with respect to the
tendon:
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Parallel.
Fusiform (cigar shaped).
Circular.
Triangular.
Pennate (feather shaped).
Effects of Fascicle
Arrangement
 Fascicular arrangement affects a muscle’s
power and range of motion.
 The longer the muscles in a fiber, the greater
the range of motion they can produce.
 The power of a muscle depends upon it’s
cross-sectional area (a short muscle fiber can
contract as powerfully as a long one).
Coordination Within Muscle
Groups
 Movements are typically the result of several
skeletal muscles acting as a group.
 Most skeletal muscles are arranged in opposing
(antagonistic) pairs at joints:
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Flexors – extensors, abductors – adductors, etc.
 One muscle is called the prime mover (agonist)
which contracts to cause an action and the other
muscle is called the antagonist which stretches and
yields to the effects of the prime mover.
Coordination Within Muscle
Groups
 Synergists work with agonists to stabilize
intermediate joints and assist the prime mover.
 Fixators stabilize the origin of the prime mover so
that the prime mover can operate more efficiently.
 In limbs, a compartment is a group of skeletal
muscles, and their associated blood vessels and
nerves, that have a common function.
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I.E. In the upper limbs with have flexor compartments
and extensor compartments.
Benefits of Stretching
 Improved physical performance – greater R.O.M.
 Decreased risk of injury – decreases the resistance
in tissues.
 Reduced muscle soreness.
 Improved posture – stretching helps realign soft
tissues.
 Muscles should be stretched at a point of slight
discomfort (not pain) for 15-30 seconds.
Muscles of Facial Expression
 Scalp muscles
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Occipitofrontalis
Frontal belly
 Occipital belly
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Muscles of Facial Expression
 Mouth muscles
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Orbicularis oris
Zygomaticus major
Zygomaticus minor
Levator labii superioris
Depressor labii inferioris
Depressor anguli oris
Buccinator
Muscles of Facial Expression
 Neck muscle
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Platysma
 Orbit and eyebrow muscles
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Orbicularis Oculi
Corrugator Supercilii
Levator palpebrae superioris
Frontalis
 Origin – Epicranial aponeurosis
 Insertion – skin above the eye
 Action – draws skin anteriorly, raises
eyebrows, and wrinkles skin of the forehead
Occipitalis
 Origin – occipital bone and mastoid process
of the temporal bone
 Insertion – epicranial aponeurosis
 Action – draws scalp posteriorly
Orbicularis Oris
 Origin – surrounding the opening of the
mouth
 Insertion – skin at the corner of the mouth
 Action – closes and protrudes lips,
compresses lips against the teeth, and shapes
lips during speech
Buccinator
 Origin – maxilla and mandible
 Insertion – orbicularis oris
 Action – draws the angle of the mouth
laterally and inferiorly as in opening the
mouth
Platysma
 Origin – fascia over deltoid and pectoralis
major muscles
 Insertion – mandible, muscles around the
angle of the mouth and the skin of the lower
face
 Action – draws the outer part of the lower lip
inferiorly and posteriorly as in pouting and
depresses the mandible
Orbicularis Oculi
 Origin – medial wall of orbit
 Insertion – circular path around orbit
 Action – closes eye
Bell’s Palsy (Facial Paralysis)
 Unilateral paralysis of the muscles of facial
expression.
 Due to damage or disease of the facial nerve
(cranial nerve VII).
 The causes is unknown; However,
inflammation of the facial nerve or infection
by herpes simplex are suggested causes.
Bell’s Palsy (Facial Paralysis)
 The person cannot wrinkle the forehead,
close the eye, or pucker the lips on the
affected side.
 Difficulty in swallowing and drooling often
occur.
 80% recover within a few weeks to a few
months; However, for some the paralysis is
permanent.
Muscles That Move the
Eyeballs – Extrinsic Eye
Muscles
 Superior Rectus
 Inferior Rectus
 Lateral Rectus
 Medial Rectus
 Superior oblique
 Inferior oblique
Strabismus
 A condition in which the eyes are not
properly aligned.
 A lesion of the oculomotor nerve (cranial
nerve III) or the abducens nerve (cranial
nerve VI).
Muscles That Move the
Mandible
 Masseter
 Temporalis
 Medial Pterygoid
 Lateral Pterygoid
Masseter
 Origin – maxilla and zygomatic arch
 Insertion – angle and ramus of mandible
 Action – elevates mandible and retracts
mandible (closes mouth)
Temporalis
 Origin – temporal bone
 Insertion – coronoid process and ramus of
mandible
 Action – elevates and protracts mandible and
moves mandible from side to side
Muscle That Move The Tongue
 Genioglossus
 Styloglossus
 Palatoglossus
 Hyoglossus
Muscles of the Anterior Neck
 Suprahyoid muscles
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Digastric
Stylohyoid
Mylohyoid
Geniohyoid
Muscles of the Anterior Neck
 Infrahyoid muscles
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Omohyoid
Sternohyoid
Sternothyroid
Thyrohyoid
Muscles That Move the Head
 Sternocleidomastoid
 Semispinalis Capitis
 Splenius Capitus
 Longissimus Capitis
Sternocleidomastoid
 Origin – sternum and clavicle
 Insertion – mastoid process of the temporal bone
 Action –
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Acting together (bilaterally), they flex the cervical
portion of the vertebral column, extend the head, and
elevate the sternum during forced inhalation
Acting singly (unilaterally), laterally flexes head towards
and rotates head away from the side of the contracting
muscle
Muscles That Act on the
Abdominal Wall
 Rectus Abdominus
 External oblique
 Internal oblique
 Transversus Abdominus
 Quadratus Lumborum
Rectus Abdominus
 Origin – pubic crest and pubic symphisis.
 Insertion – cartilage of the 5th to 7th ribs and
xiphoid process.
 Action – flexes vertebral column, compresses
the abdomen to aid in defecation, urination,
forced exhalation and childbirth.
External Oblique
 Origin – inferior eight ribs.
 Insertion – iliac crest and linea alba.
 Action –.
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Acting together (bilaterally) they compress the
abdomen and flex the vertebral column.
Acting singly (unilaterally), laterally flexes the
vertebral column and rotates the vertebral
column.
Muscles Used in Breathing
 Diaphragm
 External intercostals
 Internal intercostals
Muscles of the Pelvic Floor
 Levator ani
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Pubococcygeus
Iliococcygeus
 Coccygeus
Muscles of the Perineum
 Superficial Perineal muscles
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Superficial transverse perineal
Bulbospongiosis
 Deep Perineal muscles
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Deep transverse perineal
External urethral sphincter
External anal sphincter
Muscles That Move the
Pectoral Girdle
 Anterior thoracic muscles
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Subclavius
Pectoralis minor
Serratus anterior
 Posterior thoracic muscles
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Trapezius
Levator scapulae
Rhomboid major
Rhomboid minor
Muscles That Move the
Humerus
 Axial muscles that move the Humerus
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Pectoralis major
Latissimus dorsi
Muscles That Move the
Humerus
 Scapular muscles that move the Humerus
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Deltoid
Subscapularis
Supraspinatous
Infraspinatous
Teres major
Teres minor
coracobrachialis
Pectoralis Major
 Origin – clavicle, sternum, and costal
cartilages of 2nd to 6th ribs
 Insertion – greater tubercle of the humerus
 Action –
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As a whole, adducts and medially rotates arm at
the shoulder joint
Clavicular head alone flexes arm
Sternocostal head alone extends the arm
Latissimus Dorsi
 Origin – spines of the inferior six thoracic
vertebrae, lumbar vertebrae, crests of sacrum
and ilum, and inferior four ribs
 Insertion – intertubercular sulcus of humerus
 Action – extends, adducts, and medially
rotates the arm, draws arm inferiorly and
posteriorly
Deltoid
 Origin – acromial extremity of clavicle (anterior
fibers), acromion of scapula (lateral fibers), and
spine of scapula (posterior fibers)
 Insertion – deltoid tuberosity of humerus
 Action –
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Lateral fibers – abduct arm
Anterior fibers – flex and medially rotate arm
Posterior fibers – extend and laterally rotate arm
Muscles That Move the Radius
and Ulna
 Forearm flexors
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Biceps brachii
Brachialis
Brachioradialis
 Forearm extensors
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Triceps brachii
Anconeus
Muscles That Move the Radius
and Ulna
 Forearm Pronators
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Pronator teres
Pronator quadratus
 Forearm Supinator
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Supinator
Biceps Brachii
 Origin –
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Long head – tubercle above glenoid cavity of
scapula
Short head – coracoid process of scapula
 Insertion – radial tuberosity of radius
 Action – flexes forearm at elbow, supinates
forearm, and flexes arm at shoulder
Brachialis
 Origin – distal, anterior surface of humerus
 Insertion – ulnar tuberosity and coronoid
process of ulna
 Action – flexes forearm at elbow
Brachioradialis
 Origin – lateral border of distal end of
humerus
 Insertion – superior to styloid process of
radius
 Action – flexes forearm at elbow, supinates
and pronates forearm to neutral position
Triceps Brachii
 Origin – Infraglenoid tubercle of scapula,
posterior surface of humerus
 Insertion – olecranon of ulna
 Action – extends forearm at elbow, extends
arm at shoulder
Pronator Teres
 Origin – medial epicondyle of humerus and
coronoid process of ulna
 Insertion – midlateral surface of radius
 Action – pronates forearm at radioulnar
joints and weakly flexes forearm at elbow
Supinator
 Origin – lateral epicondyle of humerus and
ridge near radial notch of ulna
 Insertion – lateral surface of proximal one
third radius
 Action – supinates forearm at radioulnar
joints
Muscles That Move the Wrist,
Hand, Thumb, and Fingers
 Superficial anterior (flexor) compartment of the
forearm
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Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Flexor digitorum superficialis
 Deep anterior (flexor) compartment of the forearm
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Flexor pollicus longus
Flexor digitorum profundus
Muscles That Move the Wrist,
Hand, Thumb, and Fingers
 Superficial posterior (extensor) compartment
of the forearm
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Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
Muscles That Move the Wrist,
Hand, Thumb, and Fingers
 Deep posterior (extensor) compartment of
the forearm
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Abductor pollicis brevis
Extensor pollicis longus
Extensor indicis
Flexor Carpi Radialis
 Origin – medial epicondyle of humerus.
 Insertion – 2nd & 3rd metacarpals.
 Action – flexes and abducts hand (radial
deviation) at wrist.
Flexor Carpi Ulnaris
 Origin – medial epicondyle of humerus and
superior posterior border of ulna
 Insertion – pisiform, hamate, and base of 5th
metacarpal
 Action – flexes and adducts (ulnar deviation)
at wrist.
Extensor Digitorium
 Origin – lateral epicondyle of humerus
 Insertion – distal and middle phalanges of
each finger
 Action – extends distal and middle phalanges
of each finger and extends the hand at the
wrist
Extensor Carpi Ulnaris
 Origin – lateral epicondyle of humerus and
posterior border of ulna
 Insertion – 5th metacarpal
 Action – extends and adducts hand at wrist.
Palmaris Longus
 Origin – medial epicondyle of humerus
 Insertion – flexor retinaculum and palmar
aponeurosis (deep fascia in center of palm)
 Action – weakly flexes hand at wrist joint.
Intrinsic Muscles of the Hand
 Thenar (lateral aspect of the palm)
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Abductor pollicis
Opponens pollicis
Flexor pollicis brevis
Adductor pollicis
Intrinsic Muscles of the Hand
 Hypothenar (medial aspect of the palm)
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Abductor digiti minimi
Flexor digiti minimi brevis
Opponens digiti minimi
 Intermediate (Midpalmar)
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Lumbricals
Palmar interossei
Dorsal interossei
Carpal Tunnel Syndrome
 The carpal tunnel is a narrow passageway formed
anterior by the flexor retinaculum and posteriorly
by the carpal bones.
 The median nerve and flexor tendons pass through.
 They are vulnerable to compression, which results
in pain, numbness, and tingling in the fingers.
 It is caused by inflammation of the tendon sheaths,
fluid retention, and repetitive activities involving
flexion at the wrist.
Muscles That Move the
Vertebral Column
 Splenius
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Splenius capitis
Splenius cervicis
 Erector Spinae
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Iliocostalis group (lateral)
Longissussumus group (intermediate)
Spinalis group (medial)
Muscles That Move the
Vertebral Column
 Transversospinales
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Seminspinalis
Multifidus
Rotatores
 Segmental
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Interspinales
Intertransversarii
 Scalenes
Muscles That Move the Femur
 Psoas major
 Iliacus
 Gluteus maximus
 Gluteus medius
 Gluteus minimus
 Tensor fasciae latae
 Piriformis
Muscles That Move the Femur
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Obturator internus
Obturator externus
Superior gemellus
Quadratus femoris
Adductor longus
Adductor brevis
Adductor magnus
Pectineus
Gluteus Maximus
 Origin – iliac crest, sacrum, coccyx.
 Insertion – iliotibial tract of TFL and under
the greater trochanter of the femur.
 Action – extends thigh at hip and externally
rotates thigh.
Tensor Fasciae Latae (TFL)
 Origin – iliac crest.
 Insertion – tibia by way of the iliotibial tract.
 Action – flexes and abducts thigh at hip joint.
Adductor Longus
 Origin – pubic crest and pubic symphysis.
 Insertion – linea aspera of femur.
 Action – adducts and flexes thigh at hip joint
and medially rotates thigh.
Adductor Magnus
 Origin – inferior ramus of pubis and ischium
to ischial tuberosity.
 Insertion – linea aspera of femur.
 Action – adducts thigh at hip and medially
rotates thigh. The anterior part flexes the
thigh and the posterior part extends the thigh.
Muscles That Act on the
Femur, Tibia, and Fibula
 Medial (adductor) compartment of the thigh
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Adductor magnus
Adductor longus
Adductor brevis
Pectineus
Gracilis
Muscles That Act on the
Femur, Tibia, and Fibula
 Anterior (extensor) compartment of the thigh

Quadriceps femoris
Rectus femoris
 Vastus lateralis
 Vastus medialis
 Vastus intermedius
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Sartorius
Muscles That Act on the
Femur, Tibia, and Fibula
 Posterior (flexor) compartment of the thigh

Hamstrings
Biceps femoris
 Semitendinosus
 Semimenbranosus

Gracilis
 Origin – body and inferior ramus of pubis.
 Insertion – medial surface of body of tibia.
 Action – adducts thigh at hip, medially
rotates thigh and flexes leg at knee.
Rectus Femoris
 Origin – anterior inferior iliac spine (ASIS).
 Insertion – patella via quadriceps tendon then
tibial tuberosity.
 Action – extend the leg at the knee joint and
flexes the thigh at the hip.
Vastus Lateralis
 Origin – greater trochanter and linea aspera
of femur.
 Insertion – patella via quadriceps tendon then
tibial tuberosity.
 Action – extend the leg at the knee joint and
flexes the thigh at the hip.
Vastus Medialis
 Origin – linea aspera of femur.
 Insertion – patella via quadriceps tendon then
tibial tuberosity.
 Action – extend the leg at the knee joint and
flexes the thigh at the hip.
Vastus Intermedius
 Origin – anterior and lateral surfaces of body
of femur.
 Insertion – patella via quadriceps tendon then
tibial tuberosity.
 Action – extend the leg at the knee joint and
flexes the thigh at the hip.
Sartorius
 Origin – ASIS.
 Insertion – medial surface of body of tibia.
 Action – flexes leg at knee, flexes, abducts,
and externally rotates thigh at hip.
 “Tailor’s muscle”.
Biceps Femoris
 Origin –.
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Long head – ischial tiberosity.
Short head – linea aspera of femur.
 Insertion – head of fibula and lateral condyle
of tibia.
 Action – flexes leg at knee joint and extends
thigh at hip.
Semitendinosus
 Origin – ischial tiberosity.
 Insertion – proximal part of medial surface of
shaft of tibia.
 Action – flexes leg at knee and extends thigh
at hip.
Seminmembranosus
 Origin – ischial tiberosity.
 Insertion – medial condyle of tibia.
 Action – flexes leg at knee and extends thigh
at hip.
Muscles That Move the Foot
and Toes
 Anterior compartment of the leg
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Tibialis anterior
Extensor hallucis longus
Extensor digitorum longus
Fibularis (peroneus) tertius
 Lateral (fibular) compartment of the leg
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Fibularis (peroneus) longus
Fibularis (peroneus) brevis
Muscles That Move the Foot
and Toes
 Superficial posterior compartment of the leg
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Gastrocnemius
Soleus
Plantaris
 Deep posterior compartment of the leg
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Popliteus
Tibialis posterior
Flexor digitorum longus
Flexor hallucis longus
Tibialis Anterior
 Origin – lateral condyle and body of tibia,
interosseous membrane.
 Insertion – 1st metatarsal and first (medial)
cuneiform.
 Action – dorsiflexes foot at ankle and inverts
foot at intertarsal joints.
Extensor Digitorium Longus
 Origin – lateral condyle of tibia, anterior
surface of fibula and interosseous membrane.
 Insertion – base of 5th metatarsal.
 Action – dorsiflexes foot at ankle and everts
foot.
Peronius Longus
 Origin – head and body of fibula and lateral
condyle of tibia.
 Insertion – 1st metatarsal and 1st cuneiform.
 Action – plantar flexes foot and everts foot.
Gastrocnemius
 Origin – lateral and medial condyles of
femur and capsule of knee.
 Insertion – calcaneous by way of calcaneal
(Achille’s) tendon.
 Action – plantar flexes foot at ankle and
flexes leg at knee.
Soleus
 Origin – head of fibula and medial border of
tibia.
 Insertion – calcaneous by way of calcaneal
(Achille’s) tendon.
 Action – plantar flexes foot at ankle.
Flexor Digitorum Longus
 Origin – posterior surface of tibia.
 Insertion – distal phalanges of toes 2-5.
 Action – plantar flexes foot and flexes distal
and middle phalanges of toes 2-5.
Tibialis Posterior
 Origin – tibia, fibula, and interosseus
membrane.
 Insertion – 2nd, 3rd, & 4th metatarsals,
navicular, all cuneiforms, and cuboid.
 Action – plantar flexes foot at ankle and
inverts foot.
Flexor Hallucis Longus
 Origin – inferior two-thirds of fibula.
 Insertion – distal phalanx of great toe.
 Action – plantar flexes foot at ankle, flexes
great toe.
Shinsplint Syndrome
 Pain or soreness along the tibia, specifically the
medial, distal two-thirds.
 Caused by tendinitis of the anterior compartment
muscles, especially tibialis anterior muscle,
inflammation of the periosteum around the tibia or
stress fractures of the tibia.
 Running on hard surfaces with poorly conditioned
muscles, poor support shoes, etc. Contributes to this
condition.
Intrinsic Muscles of the Foot
 Dorsal

Extensor digitorum brevis
Intrinsic Muscles of the Foot
 Plantar

1st layer (most superficial)
Abductor hallucis
 Flexor digitorum brevis
 Abductor digiti minimi

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2nd layer
Quadratus plantae
 Lumbricals

Intrinsic Muscles of the Foot
 Plantar

3rd layer
Flexor hallucis brevis
 Adductor hallucis
 Flexor digiti minimi

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4th layer (deepest)
Dorsal interossei
 Plantar interossei

Plantar Fasciitis
 Otherwise know as painful heel syndrome.
 Inflammatory reaction due to chronic irritation of
the plantar aponeurosis at its origin on the
calcaneous.
 The most common cause of heel pain in runners.
 Tx. - Strip out the plantar aponeurosis with a tennis
ball or golf ball.
Tendons
 Patellar tendon & ligament
 Calcaneal or Achille’s tendon