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6. The Muscular System. The Muscular System. Muscles are responsible for all types of body movement Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle. The Muscular System. Skeletal Muscle Fibers Huge, cigar-shaped, multinucleate cells

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slide1

6

The Muscular System

the muscular system
The Muscular System

Muscles are responsible for all types of body movement

Three basic muscle types are found in the body

Skeletal muscle

Cardiac muscle

Smooth muscle

slide3

The Muscular System

  • Skeletal Muscle Fibers
    • Huge, cigar-shaped, multinucleate cells
    • Largest of the muscle fiber types
    • Most are attached by tendons to bones
  • Skeletal muscle fibers are also known as:
    • Striated Muscle  the fibers have obvious stripes
    • Voluntary Muscle  only muscle type subject to conscious control
characteristics of muscles
Characteristics of Muscles

Skeletal and smooth muscle cells are elongated (muscle cells = muscle fibers)

Contraction and shortening of muscles is due to the movement of microfilaments

All muscles share some terminology

Prefixes myo and mys refer to “muscle”

Prefix sarco refers to “flesh”

connective tissue wrappings of skeletal muscle
Connective Tissue Wrappings of Skeletal Muscle

Cells are surrounded and bundled by connective tissue

Endomysium encloses a single muscle fiber

Perimysium  wraps around a fascicle (bundle) of muscle fibers

Epimysium covers the entire skeletal muscle

Fascicle  bundle of muscle fibers

slide9

Musclefiber(cell)

Blood vessel

Perimysium

Epimysium

(wraps entire

muscle)

Fascicle(wrapped byperimysium)

Endomysium(betweenfibers)

Tendon

Bone

Figure 6.1

skeletal muscle attachments
Skeletal Muscle Attachments

Epimysium blends into a connective tissue attachment

Tendons  cord-like structures

Mostly collagen fibers

Often cross a joint due to toughness and small size

Aponeuroses sheet-like structures

Attach muscles indirectly to bones, cartilages, or connective tissue coverings

skeletal muscle attachments1
Skeletal Muscle Attachments

Sites of muscle attachment

Bones

Cartilages

Connective tissue coverings

smooth muscle characteristics
Smooth Muscle Characteristics

Lacks striations

Spindle-shaped cells

Single nucleus

Involuntary  no conscious control

Found mainly in the walls of hollow organs

slide13

Circular layer

of smooth muscle

(longitudinal view

of cells)

Mucosa

Longitudinal layerof smooth muscle(cross-sectionalview of cells)

Submucosa

(a)

Figure 6.2a

cardiac muscle characteristics
Cardiac Muscle Characteristics

Striations

Usually has a single nucleus

Branching cells

Joined to another muscle cell at an intercalated disc

Involuntary

Found only in the walls of the heart

slide15

Cardiacmusclebundles

(b)

Figure 6.2b

skeletal muscle functions
Skeletal Muscle Functions

Produce movement

Maintain posture

Stabilize joints

Generate heat

microscopic anatomy of skeletal muscle
Microscopic Anatomy of Skeletal Muscle

Sarcolemma  specialized plasma membrane

Myofibrils  long organelles inside muscle cell

Sarcoplasmic reticulum  specialized smooth endoplasmic reticulum

slide18

Sarcolemma

Myofibril

Nucleus

Light(I) band

Dark(A) band

(a) Segment of a muscle fiber (cell)

Figure 6.3a

microscopic anatomy of skeletal muscle1
Microscopic Anatomy of Skeletal Muscle

Myofibrils are aligned to give distinct bands

I band = light band

Contains only thin filaments

A band = dark band

Contains the entire length of the thick filaments

slide20

Z disc

H zone

Z disc

Thin (actin) filament

Thick (myosin) filament

(b) Myofibril or fibril

(complex organelle

composed of bundles

of myofilaments)

I band

M line

I band

A band

Figure 6.3b

microscopic anatomy of skeletal muscle2
Microscopic Anatomy of Skeletal Muscle

Sarcomere  contractile unit of a muscle fiber

Organization of the sarcomere

Myofilaments threadlike proteins found within each sarcomere; two types:

Thick filaments/myosin filaments

Thin filaments/actin filaments

microscopic anatomy of skeletal muscle3
Microscopic Anatomy of Skeletal Muscle

Thick filaments/myosin filaments

Composed of the protein myosin

Has ATPase enzymes to split ATP to generate power for muscle contraction

Myosin filaments have heads (extensions, or cross bridges)

Myosin and actin overlap somewhat

Thin filaments/actin filaments

Composed of the protein actin

Anchored to the Z disc

slide23

Sarcomere

M line

Z disc

Z disc

Thin (actin) filament

Thick (myosin) filament

(c) Sarcomere (segment of a myofibril)

Figure 6.3c

microscopic anatomy of skeletal muscle4
Microscopic Anatomy of Skeletal Muscle

At rest, within the A band there is a zone that lacks actin filaments

Called either the H zone or bare zone

Sarcoplasmic reticulum (SR)

Stores and releases calcium

Surrounds the myofibril

slide25

Thick filament

Bare zone

Thin filament

(d) Myofilament structure (within one sarcomere)

Figure 6.3d

stimulation and contraction of single skeletal muscle cells
Stimulation and Contraction of Single Skeletal Muscle Cells

Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus

Contractility—ability to shorten when an adequate stimulus is received

Extensibility—ability of muscle cells to be stretched

Elasticity—ability to recoil and resume resting length after stretching

the nerve stimulus and action potential
The Nerve Stimulus and Action Potential

Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract

Motor unit  one motor neuron and all the skeletal muscle cells stimulated by that neuron

slide28

Axon terminals at neuromuscular junctions

Spinal cord

Motor unit 2

Motor unit 1

Nerve

Axon ofmotorneuron

Motor neuroncell bodies

Muscle

Muscle fibers

(a)

Figure 6.4a

slide29

Axon terminals at neuromuscular junctions

Muscle fibers

Branching axonto motor unit

(b)

Figure 6.4b

the nerve stimulus and action potential1
Neuromuscular junction

Association site of axon terminal of the motor neuron and muscle

The Nerve Stimulus and Action Potential
the nerve stimulus and action potential2
The Nerve Stimulus and Action Potential

Synaptic cleft

Gap between nerve and muscle

Nerve and muscle do not make contact

Area between nerve and muscle is filled with interstitial fluid

Action potential (electrical current) reaches the axon terminal of the motor neuron

Calcium channels open and calcium ions enter the axon terminal

transmission of nerve impulse to muscle
Transmission of Nerve Impulse to Muscle

Calcium ion entry causes some synaptic vesicles to release their contents (acetylcholine, a neurotransmitter) by exocytosis

Neurotransmitter—chemical released by nerve upon arrival of nerve impulse in the axon terminal

The neurotransmitter for skeletal muscle is acetylcholine (ACh)

transmission of nerve impulse to muscle1
Transmission of Nerve Impulse to Muscle

Acetylcholine attaches to receptors on the sarcolemma of the muscle cell

In response to the binding of ACh to a receptor, the sarcolemma becomes permeable to sodium (Na+)

Sodium rushes into the cell generating an action potential and potassium leaves the cell

Once started, muscle contraction cannot be stopped

slide35

Synaptic vesicle containing ACh

Action potential reaches axonterminal of motor neuron.

1

Axon terminal of motor neuron

Mitochondrion

Ca2+

Ca2+

Synapticcleft

Sarcolemma

Fusing synapticvesicle

Sarcoplasmof muscle fiber

ACh

Folds ofsarcolemma

AChreceptor

Figure 6.5, step 1

slide36

Synaptic vesicle containing ACh

Action potential reaches axonterminal of motor neuron.

1

Axon terminal of motor neuron

Mitochondrion

Ca2+

2

Calcium (Ca2+) channelsopen and Ca2+ enters the axon terminal.

Ca2+

Synapticcleft

Sarcolemma

Fusing synapticvesicle

Sarcoplasmof muscle fiber

ACh

Folds ofsarcolemma

AChreceptor

Figure 6.5, step 2

slide37

Synaptic vesicle containing ACh

Action potential reaches axonterminal of motor neuron.

1

Axon terminal of motor neuron

Mitochondrion

Ca2+

2

Calcium (Ca2+) channelsopen and Ca2+ enters the axon terminal.

Ca2+

Synapticcleft

Sarcolemma

Fusing synapticvesicle

Sarcoplasmof muscle fiber

3

Ca2+ entry causes somesynaptic vesicles to release theircontents (acetylcholine, a neurotransmitter) by exocytosis.

ACh

Folds ofsarcolemma

AChreceptor

Figure 6.5, step 3

slide38

Synaptic vesicle containing ACh

Action potential reaches axonterminal of motor neuron.

1

Axon terminal of motor neuron

Mitochondrion

Ca2+

2

Calcium (Ca2+) channelsopen and Ca2+ enters the axon terminal.

Ca2+

Synapticcleft

Sarcolemma

Fusing synapticvesicle

Sarcoplasmof muscle fiber

3

Ca2+ entry causes somesynaptic vesicles to release theircontents (acetylcholine, a neurotransmitter) by exocytosis.

ACh

Folds ofsarcolemma

AChreceptor

4

Acetylcholine diffuses acrossthe synaptic cleft and binds toreceptors in the sarcolemma.

Figure 6.5, step 4

slide39

Ion channel insarcolemma opens;ions pass.

K+

Na+

5

ACh binds and channels open

that allow simultaneous passage

of Na+ into the muscle fiber and

K+ out of the muscle fiber. More

Na+ ions enter than K+ ions leave

and this produces a local change

in the electrical conditions of the

membrane (depolarization), which

eventually leads to an action

potential.

Figure 6.5, step 5

slide40

ACh

Degraded ACh

Ion channel closed;ions cannot pass.

Na+

ACh effects are ended by itsbreakdown in the synaptic cleft bythe enzyme acetylcholinesterase.

6

Acetylcholinesterase

K+

Figure 6.5, step 6

slide41

Neuromuscular junction

Muscle cellor fiber

Nervefiber

Small twig

Striations

Matchflame

1

Na+ diffusesinto the cell.

1

2

2

Flame ignites the twig.

Action potential spreadsrapidly along the sarcolemma.

Flame spreads rapidly along the twig.

(a)

(b)

Figure 6.6a-b

the sliding filament theory of muscle contraction
The Sliding Filament Theory of Muscle Contraction

Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament

Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere

This continued action causes a sliding of the myosin along the actin

The result is that the muscle is shortened (contracted)

slide43

Actin

Myosin

Z

Z

H

A

I

I

(a)

Z

Z

I

A

I

(b)

Figure 6.7a–b

slide44

Protein complex

In a relaxed muscle cell, the regulatory proteins formingpart of the actin myofilaments prevent myosin binding(see a). When an action potential (AP) sweeps along itssarcolemma and a muscle cell is excited, calcium ions(Ca2+) are released from intracellular storage areas (thesacs of the sarcoplasmic reticulum).

Myosinmyofilament

Actinmyofilament

(a)

Figure 6.8a

slide45

Myosin-binding site

The flood of calcium acts as the final trigger forcontraction, because as calcium binds to the regulatoryproteins on the actin filaments, the proteins undergo a change in both their shape and their position on the thinfilaments. This action exposes myosin-binding sites onthe actin, to which the myosin heads can attach (see b),and the myosin heads immediately begin seeking out binding sites.

Ca2+

Upper part of thick filament only

(b)

Figure 6.8b

contraction of skeletal muscle
Contraction of Skeletal Muscle

Muscle fiber contraction is “all or none”

Within a skeletal muscle, not all fibers may be stimulated during the same interval

Different combinations of muscle fiber contractions may give differing responses

Graded responses  different degrees of skeletal muscle shortening

contraction of skeletal muscle1
Contraction of Skeletal Muscle

Graded responses can be produced by changing:

The frequency of muscle stimulation

The number of muscle cells being stimulated at one time

types of graded responses
Types of Graded Responses

Muscle Twitch

Single, brief, jerky contraction

Sometimes result from certain nervous system problems

Not a normal muscle function

types of graded responses1
Types of Graded Responses

Summing of contractions

One contraction is immediately followed by another

The muscle does not completely return to a resting state due to more frequent stimulations

The effects are added

types of graded responses2
Types of Graded Responses

Unfused (incomplete) tetanus

Some relaxation occurs between contractions but nerve stimuli arrive at an even faster rate than during summing of contractions

Unless the muscle contraction is smooth and sustained, it is said to be in unfused tetanus

types of graded responses3
Types of Graded Responses

Fused (complete) tetanus

No evidence of relaxation before the following contractions

Frequency of stimulations does not allow for relaxation between contractions

The result is a smooth and sustained muscle contraction

muscle response to strong stimuli
Muscle Response to Strong Stimuli

Muscle force depends upon the number of fibers stimulated

More fibers contracting results in greater muscle tension

Muscles can continue to contract unless they run out of energy

energy for muscle contraction
Energy for Muscle Contraction

Initially, muscles use stored ATP for energy

ATP bonds are broken to release energy

Only 4–6 seconds worth of ATP is stored by muscles

After this initial time, other pathways must be utilized to produce ATP

energy for muscle contraction1
Energy for Muscle Contraction

Direct phosphorylation of ADP by creatine phosphate (CP)  unique, high energy molecule found only in muscle fibers

After ATP is depleted, ADP is left

CP transfers a phosphate group to ADP, to regenerate ATP

CP supplies are exhausted in less than 15 seconds

About 1 ATP is created per CP molecule

energy for muscle contraction2
Energy for Muscle Contraction

Aerobic respiration

Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP)

A series of metabolic pathways occur in the mitochondria

This is a slower reaction that requires continuous oxygen

Carbon dioxide and water are produced

energy for muscle contraction3
Energy for Muscle Contraction

Anaerobic glycolysis and lactic acid formation

Reaction that breaks down glucose without oxygen

Glucose is broken down to pyruvic acid to produce about 2 ATP

Pyruvic acid is converted to lactic acid

This reaction is not as efficient, but is fast

Huge amounts of glucose are needed

Lactic acid produces muscle fatigue

muscle fatigue and oxygen deficit
Muscle Fatigue and Oxygen Deficit

When a muscle is fatigued, it is unable to contract even with a stimulus

Common cause for muscle fatigue is oxygen debt

Oxygen must be “repaid” to tissue to remove oxygen deficit

Oxygen is required to get rid of accumulated lactic acid

Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

types of muscle contractions
Types of Muscle Contractions

Isotonic contractions

Myofilaments are able to slide past each other during contractions

The muscle shortens and movement occurs

Example: bending the knee; rotating the arm

Isometric contractions

Tension in the muscles increases

The muscle is unable to shorten or produce movement

Example: push against a wall with bent elbows

muscle tone
Muscle Tone

The state of continuous partial contractions

Some fibers are contracted even in a relaxed muscle

Different fibers contract at different times to provide muscle firmness and to be constantly ready

slide68

Homeostatic Imbalance

  • If the nerve supply to a muscle is destroyed (accident), the muscle is no longer stimulated in this manner, and it loses tone and becomes paralyzed
    • Flaccid  soft and flabby
    • Atrophy  waste away
effect of exercise on muscles
Effect of Exercise on Muscles

Exercise increases muscle size, strength, and endurance

Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue

Makes body metabolism more efficient

Improves digestion, coordination

Resistance (isometric) exercise (weight lifting) increases muscle size and strength

five golden rules of skeletal muscle activity
Five Golden Rules of Skeletal Muscle Activity

1. With a few exceptions, all skeletal muscles cross at least one joint.

2. Typically, the bulk of a skeletal muscle lies proximal to the joint crossed.

3. All skeletal muscles have at least two attachments: the origin and the insertion.

4. Skeletal muscles can only pull; they never push.

5. During contraction, a skeletal muscle insertion moves toward the origin.

muscles and body movements
Muscles and Body Movements

Movement is attained due to a muscle moving an attached bone

Muscles are attached to at least two points

Origin

Attachment to an immovable bone

Insertion

Attachment to a movable bone

slide73

Musclecontracting

Origin

Brachialis

Tendon

Insertion

Figure 6.12

types of body movements
Types of Body Movements

Flexion

Decreases the angle of the joint

Brings two bones closer together

Typical of bending hinge joints like knee and elbow or ball-and-socket joints like the hip

Extension

Opposite of flexion

Increases angle between two bones

Typical of straightening the elbow or knee

Extension beyond 180° is hypertension

types of body movements1
Types of Body Movements

Rotation

Movement of a bone around its longitudinal axis

Common in ball-and-socket joints

Example is when you move atlas around the dens of axis (shake your head “no”)

types of body movements2
Types of Body Movements

Abduction

Movement of a limb away from the midline

Adduction

Opposite of abduction

Movement of a limb toward the midline

types of body movements3
Types of Body Movements

Circumduction

Combination of flexion, extension, abduction, and adduction

Common in ball-and-socket joints

special movements
Special Movements

Dorsiflexion

Lifting the foot so that the superior surface approaches the shin (toward the dorsum)

Plantar flexion

Depressing the foot (pointing the toes)

“Planting” the foot toward the sole

special movements1
Special Movements

Inversion

Turn sole of foot medially

Eversion

Turn sole of foot laterally

special movements2
Special Movements

Supination

Forearm rotates laterally so palm faces anteriorly

Radius and ulna are parallel

Pronation

Forearm rotates medially so palm faces posteriorly

Radius and ulna cross each other like an X

special movements3
Special Movements

Opposition

Move thumb to touch the tips of other fingers on the same hand

types of muscles
Types of Muscles

Prime mover  muscle with the major responsibility for a certain movement

Antagonist  muscle that opposes or reverses a prime mover

Synergist  muscle that aids a prime mover in a movement and helps prevent rotation

naming skeletal muscles
Naming Skeletal Muscles

By direction of muscle fibers

Example:Rectus (straight)

By relative size of the muscle

Example:Maximus (largest)

naming skeletal muscles1
Naming Skeletal Muscles

By location of the muscle

Example:Temporalis (temporal bone)

By number of origins

Example:Triceps (three heads)

naming skeletal muscles2
Naming Skeletal Muscles

By location of the muscle’s origin and insertion

Example:Sterno (on the sternum)

By shape of the muscle

Example:Deltoid (triangular)

By action of the muscle

Example:Flexor and extensor (flexes or extends a bone)

slide95

Orbicularis oris

Deltoid

Pectoralis major

(d) Circular

(a) Convergent

(e) Multipennate

Biceps brachii

(d)

Rectus femoris

(e)

(a)

(b)

(c)

(b) Fusiform

(f) Bipennate

Sartorius

Extensor digitorum longus

(f)

(g)

(c) Parallel

(g) Unipennate

Figure 6.15

head and neck muscles
Head and Neck Muscles

Facial muscles

Frontalis—raises eyebrows

Orbicularis oculi—closes eyes, squints, blinks, winks

Orbicularis oris—closes mouth and protrudes the lips

Buccinator—flattens the cheek, chews

Zygomaticus—raises corners of the mouth

Chewing muscles

Masseter—closes the jaw and elevates mandible

Temporalis—synergist of the masseter, closes jaw

head and neck muscles1
Head and Neck Muscles

Neck muscles

Platysma—pulls the corners of the mouth inferiorly

Sternocleidomastoid—flexes the neck, rotates the head

slide98

Cranial

aponeurosis

Frontalis

Temporalis

Orbicularis

oculi

Occipitalis

Zygomaticus

Buccinator

Masseter

Orbicularis

oris

Sternocleidomastoid

Trapezius

Platysma

Figure 6.16

muscles of trunk shoulder arm
Muscles of Trunk, Shoulder, Arm

Anterior muscles

Pectoralis major—adducts and flexes the humerus

Intercostal muscles

External intercostals—raise rib cage during inhalation

Internal intercostals—depress the rib cage to move air out of the lungs when you exhale forcibly

slide100

Clavicle

Deltoid

Sternum

Pectoralismajor

Bicepsbrachii

Brachialis

Brachio-radialis

(a)

Figure 6.17a

muscles of trunk shoulder arm1
Muscles of Trunk, Shoulder, Arm

Muscles of the abdominal girdle

Rectus abdominis—flexes vertebral column and compresses abdominal contents (defecation, childbirth, forced breathing)

External oblique—flex vertebral column; rotate trunk and bend it laterally

Internal oblique—flex vertebral column; rotate trunk and bend it laterally

Transversus abdominis—compresses abdominal contents

slide102

Pectoralismajor

Rectusabdominis

Transversusabdominis

Internaloblique

Externaloblique

Aponeurosis

(b)

Figure 6.17b

muscles of trunk shoulder arm2
Muscles of Trunk, Shoulder, Arm

Posterior muscles

Trapezius—elevates, depresses, adducts, and stabilizes the scapula

Latissimus dorsi—extends and adducts the humerus

Erector spinae—back extension

Quadratus lumborum—flexes the spine laterally

Deltoid—arm abduction

muscles of trunk shoulder arm3
Muscles of Trunk, Shoulder, Arm

Muscles that arise from the shoulder girdle and cross the shoulder joint to insert into the humerus include:

Pectoralis major

Latissimus dorsi

Deltoid

slide105

Occipital bone

Sternocleidomastoid

Spine of scapula

Trapezius

Deltoid (cut)

Deltoid

Triceps

brachii

Latissimus

dorsi

Humerus

Olecranon

process of

ulna (deep

to tendon)

(a)

Figure 6.18a

slide106

C7

T1

Erector spinae

• Iliocostalis

• Longissimus

• Spinalis

QuadratusIumborum

(b)

Figure 6.18b

muscles of the upper limb
Muscles of the Upper Limb

Biceps brachii—supinates forearm, flexes elbow

Brachialis—elbow flexion

Brachioradialis—weak muscle; elbow flexion

Triceps brachii—elbow extension (antagonist to biceps brachii)

slide108

Clavicle

Deltoid

Sternum

Pectoralismajor

Bicepsbrachii

Brachialis

Brachio-radialis

(a)

Figure 6.17a

slide109

Occipital bone

Sternocleidomastoid

Spine of scapula

Trapezius

Deltoid (cut)

Deltoid

Triceps

brachii

Latissimus

dorsi

Humerus

Olecranon

process of

ulna (deep

to tendon)

(a)

Figure 6.18a

muscles of the upper limb1
Muscles of the Upper Limb

Muscles of the forearm, which insert on the hand bones and cause their movement include:

Flexor carpi—wrist flexion

Flexor digitorum—finger flexion

Extensor carpi—wrist extension

Extensor digitorum—finger extension

muscles of the lower limb
Muscles of the Lower Limb

Muscles causing movement at the hip joint include:

Gluteus maximus—hip extension

Gluteus medius—hip abduction, steadies pelvis when walking

Iliopsoas—hip flexion, keeps the upper body from falling backward when standing erect

Adductor muscles—adduct the thighs

slide112

Gluteus medius

Gluteus maximus

Adductormagnus

Iliotibial tract

Biceps femoris

Hamstring group

Semitendinosus

Semimembranosus

Gastrocnemius

(a)

Figure 6.20a

slide113

Posterior superioriliac spine

IIiac crest

Safe area ingluteus medius

Gluteus maximus

Sciatic nerve

(b)

Figure 6.20b

slide114

12ththoracic vertebra

12th rib

Iliac crest

Psoas major

lliopsoas

lliacus

5thlumbar vertebra

Anterior superior

iliac spine

Sartorius

Adductorgroup

Rectus femoris

Vastus lateralis

Quadriceps

Vastus medialis

Patella

Patellarligament

(c)

Figure 6.20c

muscles of the lower limb1
Muscles of the Lower Limb

Muscles causing movement at the knee joint

Hamstring group—thigh extension and knee flexion

Biceps femoris

Semimembranosus

Semitendinosus

slide116

Gluteus medius

Gluteus maximus

Adductormagnus

Iliotibial tract

Biceps femoris

Hamstring group

Semitendinosus

Semimembranosus

Gastrocnemius

(a)

Figure 6.20a

muscles of the lower limb2
Muscles of the Lower Limb

Muscles causing movement at the knee joint

Sartorius—flexes the thigh

Quadriceps group—extends the knee

Rectus femoris

Vastus muscles (three)

slide118

12ththoracic vertebra

12th rib

Iliac crest

Psoas major

lliopsoas

lliacus

5thlumbar vertebra

Anterior superior

iliac spine

Sartorius

Adductorgroup

Rectus femoris

Vastus lateralis

Quadriceps

Vastus medialis

Patella

Patellarligament

(c)

Figure 6.20c

slide119

Inguinalligament

Adductormuscles

Sartorius

Vastuslateralis

(d)

Figure 6.20d

muscles of the lower limb3
Muscles of the Lower Limb

Muscles causing movement at ankle and foot

Tibialis anterior—dorsiflexion, foot inversion

Extensor digitorum longus—toe extension and dorsiflexion of the foot

Fibularis muscles—plantar flexion, foot eversion

Soleus—plantar flexion

slide121

Fibularis longus

Tibia

Fibularis brevis

Soleus

Tibialis anterior

Extensor digitorumlongus

Fibularis tertius

(a)

Figure 6.21a

slide122

Gastrocnemius

Soleus

Calcaneal (Achilles)tendon

Medial malleolus

Lateralmalleolus

(b)

Figure 6.21b