Chapter 11 Lecture Outline Part 1 of 2

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Chapter 11

Lecture Outline

Part 1 of 2

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Introduction: Axial and

Appendicular Muscles

• Axial muscles

– Have both origins and insertions on axial skeleton

– Support and move the head and vertebral column

– Function in facial expression, breathing, chewing and swallowing

– Support and protect abdominal and pelvic organs

• Appendicular muscles

– Control movements of upper and lower limbs

– Control movements of pectoral and pelvic girdles

– Organized into groups based on locations

2

Figure 11.1a

3

Body Musculature: Anterior View

Figure 11.1b

4

Body Musculature: Posterior View

11.1a Origin and Insertion

• Origin

– Less movable attachment of a muscle

– Typically the more proximal attachment

• Insertion

– More movable attachment of a muscle: pulled toward

origin when muscle contracts

– Typically the more distal attachment

5

Figure 11.2

6

11.1a Origin and Insertion

• Origins of biceps

brachii are on scapula

• Insertion of biceps

brachii is on radius

• Contraction pulls

forearm toward

shoulder

11.1b Organizational Patterns of

Skeletal Muscle Fibers

• Varied organization of fascicles (bundles of muscle fibers)

– Circular muscles: concentrically arranged fascicles

o Create a sphincter

o Control material passage through an opening

– Parallel muscles: fascicles run parallel to muscle’s long axis

o Sometimes have an expanded central belly

o High endurance

– Convergent muscles: fascicles merge toward a common attachment site

o Common site might be a tendon, sheet, or raphe (seam)

o Can pull in varying directions, but not as hard as parallel muscles of same size

– Pennate muscles: fascicles organized as if part of a large feather

o Fibers pull at an angle to the tendon

o Generate more tension but don’t pull their tendons as far as parallel muscles of

same size

o Three subtypes: unipennate, bipennate, and multipennate

7

Figure 11.3

8

11.1b Organizational Patterns of Skeletal Muscle Fibers

Unipennate: All fibers on

same side of tendon Bipennate: Fibers on both

sides of tendon

Multipennate: Tendon

branches within muscle

11.1c Actions of Skeletal Muscles

• Muscles grouped by primary actions

– Agonist

o Prime mover; muscle that contracts to produce a movement

o E.g., triceps brachii is agonist for forearm extension

– Antagonist

o Muscle whose contraction opposes that of the agonist

– This allows for smooth movement of controlled speed

o E.g., biceps brachii, is antagonist for forearm extension

– Synergist

o Muscle that assists agonist by contributing tension or stabilizing point

of origin (acting as fixators)

o E.g., biceps brachii and brachialis muscle work synergistically to flex

elbow joint

9

11.2 Skeletal Muscle Naming

• How are muscles named?

– Muscle action: indicates muscle’s primary function

o E.g., flexor digitorum longus flexes digits

– Specific body regions: indicates muscle location

o E.g., rectus femoris is near the femur

–Muscle attachments: indicates origins and/or insertions

o E.g., sternocleidomastoid originates on the sternum and clavicle and

inserts on the mastoid process

–Orientation of muscle fibers: indicates organization of muscle

fascicles

o E.g., rectus abdominis is composed of fibers running in vertically

straight (“rectus”) orientation

10

11.2 Skeletal Muscle Naming

• How are muscles named? (continued)

– Muscle shape

o E.g., deltoid is shaped like a triangular delta symbol

o E.g., abductor pollicis longus is a long muscle

–Muscle size

o E.g., gluteus maximus is the largest of the buttocks muscles

–Muscle heads/tendons of origin: indicates how many tendons

are present at less movable attachment

o E.g., triceps brachii has three heads attaching by tendons to the

skeleton

11

Clinical View: Intramuscular Injections

• One route of medication administration

• May be inserted into muscle with a syringe

• Medication to cardiovascular system through muscle’s blood

vessels

• Allows large amount of medication given at once

• Ensures slower and more uniform delivery than orally or

intravenously

• Common sites: deltoid, gluteus medius, quadriceps

12

11.3a Muscles of Facial Expression

• Characteristics

– Insert into superficial fascia of skin of face

– Cause skin to move (facial expression) during contraction

– Most are innervated by facial nerve (CN VII)

13


• Muscles of forehead, scalp, and eyebrows

– Occipitofrontalis muscle

o Connects with epicranial aponeurosis (galea aponeurotica) to form

epicranius

o Frontal belly raises eyebrows

o Occipital belly retracts scalp slightly

– Corrugator supercilii muscle

o Draws eyebrows together

– Orbicularis oculi

o Circular muscle fibers surround orbit

o Closes eye

– Levator palpebrae superioris

o Elevates upper eyelid

14


• Muscles associated with the nose

– Nasalis

o Elevates corners of the nostrils for “flared” nostrils

– Procerus

o Wrinkles nose in distaste

o Continuous with frontal belly of occipitofrontalis

muscle

16

Procerus

10-17


• Muscles associated with the mouth– Orbicularis oris

o Closes mouth, puckers lips

– Depressor labii inferioris

o Pulls lower lip inferiorly

– Depressor anguli oris

o Pulls corners of the mouth inferiorly to frown

– Levator labii superioris

o Pulls upper lip superiorly

– Levator anguli oris

o Pulls corners of mouth superiorly and laterally

o Works with zygomaticus major and minor in smiling

18


• Muscles associated with the mouth (continued)

– Risorius

o Pulls corner of the lips laterally

– Mentalis

o Protrudes lower lip

– Platysma

o Tenses skin of neck and pulls lower lip inferiorly

– Buccinator

o Compresses cheek against the teeth when chewing

19

Figure 11.5a 20

Muscles of Facial Expression

Figure 11.5b 21

Muscles of Facial Expression

Clinical View: Idiopathic Facial Nerve

Paralysis (Bell Palsy)

• May be without known cause (idiopathic)

• Also known as Bell palsy

• Facial nerve inflamed and compressed

– Muscles on same side paralyzed

• Concern of eyes drying out and becoming damaged

• Prednisone often used to reduce swelling

• Level and timing of recovery varies

22

11.3b Extrinsic Eye Muscles

• Extrinsic eye muscles are extraocular

– Insert onto outer surface of the eye and move it

– Six muscles: four rectus and two oblique

• Rectus eye muscles originate from common tendinous ring

– Medial rectus pulls eye medially

o Innervated by CN III (oculomotor)

– Lateral rectus pulls eye laterally

o Innervated by CN VI (abducens)

– Inferior rectus pulls eye inferiorly and medially


– Superior rectus pulls eye superiorly and medially


23

11.3b Extrinsic Eye Muscles

• Oblique eye muscles

– Inferior oblique elevates and turns eye laterally


– Superior oblique depresses and turns the eye laterally

o Passes through pulleylike loop, trochlea

o Innervated by CN IV (trochlear)

24

Figure 11.7a25

Extrinsic Muscles of the Eye

Figure 11.7b

26

Extrinsic Muscles of the Eye

Clinical View: Cranial III, IV, and VI

• Eye movements tested together with H-pattern

• Weakness (ptosis) of the eye in one direction can

indicate cranial nerve involvement

• Double vision, Lazy eye, Cross eyed

27

11.3c Muscles of the Oral Cavity and Pharynx

• Muscles of mastication (chewing)

– Four paired muscles move mandible at temporomandibular

joint (TMJ)

– All four are innervated by CN V (trigeminal)

– Temporalis

o Elevates and pulls the mandible posteriorly (retracts)

– Masseter

o Elevates and pulls the mandible anteriorly (protracts)

o Most powerful and important masticatory muscle

–Medial and lateral pterygoid

o Side to side movement of mandible

o Medial pterygoid also helps with elevation of mandible

o Lateral pterygoid helps with depression of the mandible

28

Figure 11.829

Muscles of Mastication

11.3c Muscles of the Oral Cavity and Pharynx

• Muscles that move the tongue

– Left and right genioglossus

o Protract (stick out) the tongue

– Left and right styloglossus

o Elevate and retract the tongue

– Left and right hyoglossus

o Depress and retract the tongue

– Left and right palatoglossus

o Elevate posterior portion of the tongue

30

31

Muscles That Move the Tongue

Figure 11.9

11.3d Muscles of the Anterior Neck:

The Hyoid Muscles

• Suprahyroid muscles: above hyoid bone

– Elevate hyoid bone during swallowing or speaking

– Digastric: has two bellies, anterior and posterior

o Also helps depress mandible

– Geniohyoid

o Elevates the hyoid bone

– Mylohyoid

o Provides muscular floor of mouth; also raises it up

– Stylohyoid: attaches to styloid process of temporal bone

o Elongates oral cavity during swallowing

32

11.3d Muscles of the Anterior Neck:

The Hyoid Muscles

• Infrahyoid muscles: inferior to hyoid bone

– Depress hyoid bone or thyroid cartilage of larynx as swallowing

finishes

– Omohyoid

o Depresses hyoid by pulling it toward scapula

– Sternohyoid

o Depresses hyoid by pulling it toward sternum

– Sternothyroid

o Depresses thyroid cartilage by pulling it toward sternum

– Thyrohyoid: extends from thyroid cartilage to hyoid

o Depresses hyoid bone and elevates thyroid cartilage

o Closes off larynx during swallowing

33

Figure 11.11 34

Muscles of the Anterior Neck

11.3e Muscles That Move the Head and Neck

• Anterolateral neck muscles

– Generally act to flex neck

– Sternocleidomastoid: from sternum and clavicle to mastoid

o Unilateral (one side) flexion of head to contracting muscle’s side and

contralateral rotation of head to opposite side

– Anterior, middle, and posterior scalene muscles

• Work with sternocleidomastoid to flex neck

• Pull cervical vertebrae toward 1st and 2nd ribs

• Elevate 1st and 2nd ribs during forced inhalation

• Tighten with paradoxical breathing

35

Figure 11.12 36

Muscles That Move the Head and Neck

11.3e Muscles That Move the Head and Neck

• Posterior neck muscles

– Generally act to extend the neck

– Trapezius

o Primary function is to help move pectoral girdle, but also helps extend neck

– Splenius capitis, splenius cervicis, semispinalis capitis,

longissimus capitis

o When contracted bilaterally, extend neck

o When contracted unilaterally, turn head to same side

– Suboccipital muscles

o Obliquus capitis superior, obliquus capitis inferior turn head to same side

o Rectus capitis posterior major, rectus capitis posterior minor extend neck

37

Posterior Neck Muscles

38

Clinical View: Congenital

Muscular Torticollis

• Newborn with shortened sternocleidomastoid

• May persist into childhood

• From birth trauma or prenatal position

• Head tilts to affected side and chin to unaffected side

• Treatments include

– Physical therapy

– Botulinum toxin, which impairs contraction of affected muscle

– Chiropractic care

39

Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill EducationCopyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education

What did you learn?

• Which muscles open and

close the eyes?

• Which cranial nerve controls

the lateral rectus muscle?

• What action does contraction

of the masseter cause?

• What muscle is affected in

Torticollis and what clinical

presentation might be

present?

40

11.4 Muscles of the Vertebral Column

• Muscles of the vertebral column

– Complex, multiple origins and insertions, overlapping muscles

– Erector spinae

o Maintain upright posture; if bilaterally contracted, vertebral column extends

o If unilaterally contracted, lateral flexion toward that side

o Three groups of erector spinae muscles from lateral to medial

– Iliocostalis group

– Longissimus group

– Spinalis group

– Quadratus lumborum muscles

o Extends vertebral column when bilaterally contracted

o Laterally flexes column when unilaterally contracted

o Located primarily in the lumbar region

41

Figure 11.14 42

Deep Muscles of the Vertebral Column

11.5 Muscles of Respiration

• Muscles of respiration

– Diaphragm

o Internally placed dome-shaped muscle that partitions

thoracic and abdominal cavities

oMost important muscle associated with breathing

oMuscle fibers converge toward fibrous central tendon

oOpenings for vena cava, aorta, and esophagus

oContracts during inspiration

oCentral tendon pulled inferiorly, increasing dimension

of thoracic cavity

43

Figure 11.15c-d

44

Muscles of Respiration

11.5 Muscles of Respiration

• Muscles of respiration

– External intercostals

oElevate ribs during inspiration, expanding cavity

– Internal intercostals

oDeep to external intercostals

oFibers at right angles to external intercostals

oDepress ribs during forced expiration

– Transversus thoracis

oDepresses ribs during forced expiration

45

Figure 11.15a

46

Muscles of Respiration

11.6 Muscles of the Abdominal Wall

• Muscles of the abdominal wall

– Compress and hold abdominal organs in place

– External oblique

o Ipsilateral flexion and Contralateral rotation

– Internal oblique

o Ipsilateral flexion and Ipsilateral rotation

– Transversus abdominis

o Stabilizes the vertebral column (core muscle)

– Rectus abdominis

o Partitioned into four segments by fibrous tendinous intersections

o Enclosed within fibrous sleeve, rectus sheath

– Formed from aponeuroses of external and internal oblique,

transversus abdominis

– Rectus sheaths of two sides connected by fibrous strip, linea alba

47

Figure 11.16a48

Muscles of the Abdominal Wall

49

Muscles of the Abdominal Wall

Figure 11.16b

• Portion of viscera protrudes through weak

point of abdominal wall

• Inguinal hernia

– Loop of small intestine protrudes through

superficial inguinal ring

– More likely to occur in males since their inguinal

canals are larger to accommodate spermatic cord

– High abdominal pressure (e.g., straining to lift

something heavy) can push intestine into canal

– Physicians test for it by palpating inguinal ring

while patient coughs (cough raises abdominal

pressure)

Clinical View: Hernias

50

Muscles of the Pelvic Floor

• Perineum

– Diamond-shaped region

between lower appendages

– Bounded by pubic

symphysis, coccyx, ischial

tuberosities

– Contains two triangles

divided by transverse line

between ischial tuberosities

o Urogenital triangle

contains external genitalia

and urethra

o Anal triangle contains anus

51Figure 11.17b,c (left)

11.8a Muscles That Move

the Pectoral Girdle

• Anterior thoracic muscles

– Pectoralis minor

oDeep to pectoralis major

oHelps depress and protract scapula; hunches shoulders

– Serratus anterior

oFan-shaped muscle between ribs and scapula

oProtracts, stabilizes scapula

– Subclavius

oExtends from clavicle to first rib

oStabilizes and depresses scapula

52

53

Muscles That Move Pectoral Girdle and Arm

Figure 11.21a

11.8a Muscles That Move the Pectoral Girdle

• Posterior thoracic muscles

– Levator scapulae

o Attaches to cervical vertebrae and scapula

– Tends to be involved in tension headaches

o Elevates and inferiorly rotates the scapula

– Rhomboid major and minor

o Runs inferolaterally from vertebrae to scapula, deep to trapezius

o Helps elevate, retract, and inferiorly rotate the scapula

– Trapezius

o Diamond-shaped muscle extending from skull and vertebral column to

pectoral girdle

o Can elevate, depress, retract, or rotate scapula

54

Figure 11.21b55

Muscles That Move Pectoral Girdle and Arm

56

Actions of Some Thoracic Muscles on the Scapula

Figure 11.20a

11.8b Muscles That Move the

Glenohumeral Joint/Arm

• Eleven muscles cross the glenohumeral joint and

move the humerus– Deltoid

o Prime abductor of the arm

o Its anterior fibers flex and medially rotate arm

o Its lateral fibers abduct the arm

o Its posterior fibers extend and laterally rotate arm

– Latissimus dorsi

o Prime arm extensor; adducts, medially rotates

– Pectoralis major

o Prime arm flexor; adducts, medially rotates

– Coracobrachialis

o Flexes and adducts the arm

57

11.8b Muscles That Move the

Glenohumeral Joint/Arm

• Triceps brachii

o Helps extend and adduct the arm

• Biceps brachii

o Assists in flexing the arm

• Teres major

– Extends, adducts, medially rotates arm

• Rotator cuff muscles

– Subscapularis

o Medially rotates arm

– Supraspinatus

o Abducts the arm

– Infraspinatus and teres minor

o Adduct and laterally rotate arm

58

59

Rotator Cuff Muscles

Figure 11.22

• Subscapularis

helps in wind up

for pitch

• Supraspinatus

helps in

executing pitch

delivery

• Infraspinatus and

teres minor slow

the arm at end of

pitch

• Result of trauma or disease

• Can be caused by repetitive use

• Can be caused by falling on the shoulder or lifting too heavy of an

object

• Supraspinatus most commonly involved

• Symptoms are swelling, tenderness, and pain with movement

• Especially common in baseball players

• May require physical therapy or surgical repair

Clinical View: Rotator Cuff Injuries

60

11.8c Arm and Forearm Muscles That

Move the Elbow Joint/Forearm

• Muscles of the arm’s anterior compartment

– Biceps brachii

oTwo-headed muscle on anterior humerus

oFlexes and supinates forearm; weakly helps flex humerus

– Brachialis

oDeep to biceps brachii

oMost powerful flexor of forearm (prime mover)

– Brachioradialis

oLocated on anterolateral forearm

oSynergist in elbow flexion61

62

Anterior Muscles with Actions at Elbow

Figure 11.24



• Muscles of the arm’s posterior compartment

– Triceps brachii

oLarge three-headed muscle on posterior arm

oMajor extensor of forearm; also helps extend humerus

– Anconeus

oWeak elbow extensor (synergist)

oCrosses posterolateral region of elbow

63

64

Posterior Muscles with Actions at Elbow

Figure 11.25

• Muscles of the forearm that act on the elbow

joint

– Pronator teres and pronator quadratus

oRotate the radius across the ulna to pronate forearm

oLocated in anterior compartment of forearm

– Supinator

oSupinates forearm

oLocated in posterior compartment of forearm

65



Figure 11.2666

Forearm Muscles That Supinate or Pronate

11.8d Forearm Muscles That Move

the Wrist Joint, Hand, and Fingers

Muscles of the forearm’s anterior compartment

• Muscles originate on medial epicondyle

– Flexor carpi radialis

o Flexes wrist and abducts hand

– Palmaris longus

o Weakly assists in wrist flexion

– Flexor carpi ulnaris

o Flexes wrist and adducts hand

– Flexor digitorum superficialis

o Flexes wrist, MP, and proximal interphalangeal (PIP) joints of fingers

2–5

– Flexor digitorum profundus

o Flexes wrist, MP joints, PIP joints, and distal interphalangeal (DIP)

joints of fingers 2–567

Figure 11.27a 68

Anterior Forearm Muscles

Figure 11.27b-c69

Anterior Forearm Muscles



Muscles of forearm’s posterior compartment

• Muscles originate from lateral epicondyle

– Extensor carpi radialis longus/brevis

o Extends wrist and abducts hand

– Extensor digitorum

o Extends wrist, MP joints, PIP joints, and DIP joints of fingers 2–5

– Extensor digit minimi

o Extends the little finger

– Extensor carpi ulnaris

o Extends wrist and adducts hand

– Extensor pollicis longus/brevis

o Helps extend MP joint of the thumb

– Extensor indicis

o Extends MP, PIP, and DIP joints of index finger70

Figure 11.29a 71

Posterior Forearm Muscles

Figure 11.29b 72

Posterior Forearm Muscles

Clinical View: Lateral Epicondylitis or

Medial Epicondylitis

• Lateral Epicondylitis

– Also known as tennis elbow

– From trauma or overuse of common extensor tendon of posterior

forearm muscles

– Pain at lateral epicondyle of humerus often results from repeated

forceful contraction of forearm extensors

• Medial Epicondylitis

– Also known as golfers elbow

– From trauma or overuse of common flexor tendon of anterior forearm

muscles

– Pain at medial epicondyle of humerus often results from repeated

forceful contraction of forearm flexors

73



• Retinacula of the forearm

– Fibrous bands at the wrist formed from deep fascia

– Hold tendons close to bone

– Flexor retinaculum covers palmar surface of carpal bones

o Carpal tunnel: tight space between bones and flexor retinaculum

through which flexor tendons pass

– Extensor retinaculum superficial to dorsal surface of

carpal bones

o Extensor tendons of wrist and digits pass under it

74

Clinical View: Carpal Tunnel Syndrome

• Carpal tunnel

– Space between carpal bones and flexor retinaculum

• Flexor tendons extending through tunnel

• Median nerve extending through tunnel

• Syndrome caused by compression of nerve

• Characterized by pain and “pins and needles”

(paresthesia)

75

11.8e Intrinsic Muscles of the Hand

Intrinsic muscles of the hand: originate and insert in hand

• Thenar group: form fleshy mass at base of thumb

– Flexor pollicis brevis: flexes thumb

– Abductor pollicis brevis: abducts thumb

– Opponens pollicis: assists in opposition of thumb

• Hypothenar group: smaller fleshy mass at base of little

finger

– Flexor digiti minimi brevis: flexes little finger

– Abductor digiti minimi: abducts little finger

– Opponens digiti minimi: assists in opposition of little finger

76

Figure 11.30a77

Intrinsic Muscles of the Hand

What did you learn?• Which four muscles make up the

rotator cuff ?

• In which anatomical compartment is

the brachialis muscle found?

• What action is typically performed by

muscles in the anterior compartment

of the forearm?

• Which part of the hand makes up the

thenar group of muscles?

• What structure of the forearm is

involved in carpal tunnel syndrome?

78

11.9a Muscles that Move the Hip Joint/Thigh

• How are thigh muscles organized?

– They are bound by the fascia lata, deep fascia that partitions

them into compartments

– Anterior compartment muscles

o Extend the knee or flex the thigh

– Medial compartment muscles

o Adduct the thigh

– Lateral compartment muscle

o Abducts the thigh

– Posterior compartment muscles

o Flex knee and extend the thigh

79


• Muscles inserting on anterior thigh

– Psoas major and iliacus (collectively, iliopsoas)

oRun from lumbar vertebrae and ilium to femur

oFlex the thigh

– Sartorius “tailor muscle”

oFlex and laterally rotate the thigh and flex the knee

– Quadriceps femoris: composite muscle with four heads

o Consists of: rectus femoris, vastus lateralis, vastus medialis, vastus

intermedius

o Prime mover of knee extension

o Pulls on quadriceps tendon, which becomes patellar ligament to tibia

80

Figure 11.32a 81

Muscles of Anterior Thigh


• Muscles of the medial compartment of thigh

– Innervated by the obturator nerve

– Adductor longus, adductor brevis, gracilis,

pectineus

– Adductor magnus

• Muscle of lateral thigh

– Tensor fasciae latae

oAttaches to iliotibial tract (lateral thickening of fascia lata)

oAbducts and medially rotates the thigh

82

Figure 11.31a

83

Muscles That Act on the Hip and Thigh

Figure 11.31b84


11.9a Muscles That Move the Hip Joint/Thigh

• Muscles of the posterior thigh

– Gluteus maximus

o Chief extensor of the thigh; also laterally rotates the thigh

– Gluteus medius and gluteus minimus

o Deep to gluteus maximus

o Abduct and medially rotate the thigh

– Hamstrings: group of 3 muscles

o Biceps femoris, semimembranosous, semitendinosus

o Extend the thigh (also rotate the knee)

– Group of muscles deep to gluteal muscles

o Piriformis, superior gemellus, obturator internus, obturator externus,

inferior gemellus, and quadratus femoris

o Laterally rotate the thigh

85

Figure 11.33a 86

Muscles of Gluteal Region and Posterior Thigh

Figure 11.31c87


Clinical View: Iliotibial Band Syndrome

and Hamstring Strain

• Iliotibial Band Syndrome

– Both the Gluteus medius and Tensor fascia latae muscles insert on

the iliotibial band

– Band runs from the lateral hip to the knee

– Pain and inflammation at the lateral knee due to friction from

tightening of this band

• Hamstring Strain

– Muscle overload when the hamstring muscle undergoes eccentric

contraction

– Sprinters, basketball players, football players, soccer players

88

11.9c Leg Muscles That Move

the Ankle, Foot, and Toes

• Crural muscles: muscles located in leg that

move ankle, foot, toes

– Partitioned into anterior, lateral, and posterior

compartments

89



• Muscles of the leg’s anterior compartment

– Extensor digitorum longus

o Dorsiflexes the foot and extends toes 2–5

– Extensor hallucis longus

o Dorsiflexes the foot and extends the great toe

– Fibularis tertius

o Dorsiflexes and weakly everts the foot

– Tibialis anterior

o Primary dorsiflexor of the foot; also inverts the foot

– Extensor retinaculum

o Thickening of fascia at ankle that holds tendons close to bones

90

Figure 11.34a91

Muscles of the

Anterior Leg



• Muscles of the leg’s lateral compartment

– Both are powerful foot evertors, weak plantar flexors

oFibularis longus: inserts on plantar side of foot

oFibularis brevis: lies deep to fibularis longus, inserts onto

base of 5th metatarsal

92

Figure 11.35a 93

Muscles of the Lateral Leg



Muscles of the leg’s posterior compartment

• Superficial layer

– Gastrocnemius

o Has two bellies; forms calf

o Flexes the leg and plantar flexes the foot

– Soleus

o Broad muscle deep to gastrocnemius

o Plantar flexes the foot

– Triceps surae = gastrocnemius + soleus

o Insert at heel with calcaneal tendon

– Plantaris

o Weak leg flexor and plantar flexor of the foot

94



Muscles of the leg’s posterior compartment (continued)

• Deep layer

– Flexor digitorum longus

o Flexes the foot and the MP, PIP and DIP of joints 2–5

– Flexor hallucis longus

o Flexes the foot and great toe

– Tibialis posterior

o Plantar flexes and inverts the foot

– Popliteus

o Flexes the leg and medially rotates the tibia (lock the knee)

95

Figure 11.36a-b 96

Muscles of the Posterior Leg

Clinical View: Shin Splints, Tarsal Tunnel

Syndrome, and Achilles Tendon Rupture

• Shin splints

– Soreness along length of tibia

– Often occur in new poorly conditioned runners

– May be considered a type of compartment syndrome

• Tarsal Tunnel syndrome

– Tension of the flexor retinaculum at the medial compartment of the

foot leading to posterior tibial nerve compression

– Pain at the medial side of the ankle and into the heel/foot

– Common in overpronation

• Achilles tendon rupture

– Common in sports that involve running, jumping, pivoting, or rapid push off

97

11.9d Intrinsic Muscles of the Foot

• Intrinsic muscles of the foot originate and insert

within foot

– Support the arches, move the toes

• Dorsal group

– Extensor hallucis brevis

oExtends the MP joint of the great toe

– Extensor digitorum brevis

oExtends the MP and PIP joints of toes 2–4

98

11.9d Intrinsic Muscles of the Foot

• Plantar group

– Supported by aponeurosis formed from deep fascia

o Extends between phalanges of toes and calcaneus

– Muscles grouped into four layers from superficial to deep

1. Flexor digitorum brevis, abductor hallucis, abductor digiti

minimi

2. Quadratus plantae, lumbricals

3. Adductor hallucis, flexor hallucis brevis, flexor digiti minimi

brevis

4. Dorsal interossei, plantar interossei

99

100

Plantar Intrinsic Muscles of the Foot

Figure 11.37a-c

Figure 11.37d-e 101

Plantar Intrinsic Muscles of the Foot

• Inflammation of the plantar aponeurosis

• Associated with overexertion that stresses the fascia

– E.g., weight bearing activities, excessive body weight,

poor shoes, poor biomechanics

– Pain when stepping down from bed in the morning

Clinical View: Plantar Fasciitis

102

Chapter 11 Lecture Outline Part 1 of 2

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Transcript of Chapter 11 Lecture Outline Part 1 of 2