MUSCULAR MUSCULAR SYSTEMSYSTEM

Muscles make up 50-60% of body wt.More than 650 muscles in the body.Each muscle is made of thousands of

muscle fibers ~ the size of a fiber optic filament.

It takes 17 muscles to smile & 42 to frown.

The hardest working muscle is the heart.

The largest muscle is the Gluteus Maximus.

The longest muscle is the Sartorius.

The strongest muscle is the Masseter

The prefix myo- & mys- means muscle & the prefix sarco- means flesh so if you hear these prefixes you’ll know we’re talking about muscles.

Muscle Functions1. Create skeletal movement by contracting & relaxing.2. control of organ & vessel size 3. maintain posture & position 4. support soft tissue 5. guard entrances and exits6. maintain body temperature (85%)7. Only body tissue that can shorten (contract)

1.Skeletal – Striated– Voluntary – Stacked in Sheets

C. 3 Kinds of Muscle Tissue

AKA: Somatic Tissue

-Multinucleated-Found attached to skeleton

C. 3 Kinds of Muscle Tissue2. Cardiac aka: heart muscle#Branched cells w/Single

nuclei per cell. #Thick striations called

Intercalated discs that #Involuntary

#Cells are fused so when one cell contracts, they all contract, creating the heartbeat.

3.Smooth aka: Visceral

– Spindle shaped– Nonstriated – Involuntary

C. 3 Kinds of Muscle Tissue

-Found around hollow organs such as arteries, esophagus, stomach

1.1.ContractilityContractilityAbility to shorten and

exert tension or force2.2.Excitability Excitability

Ability to respond to stimuli

3.3.ExtensibilityExtensibility Ability to contract after

being stretched4.4.ElasticityElasticity

Ability to regain initial length after contraction

D. Muscle CharacteristicsD. Muscle Characteristics

I. OverviewI. Overview

1.1.Muscle tissue Muscle tissue (smooth, (smooth, cardiac, or skeletal) cardiac, or skeletal)

2.2.Connective tissuesConnective tissues3.3.Nervous tissueNervous tissue4.4.BloodBlood

E. Each muscle is an organ E. Each muscle is an organ comprised of:comprised of:

II. Anatomy of Skeletal II. Anatomy of Skeletal MuscleMuscle

A.Connective Tissue

1.1. Superficial Superficial Fascia:Fascia: Fibrous Fibrous

connective connective tissue tissue surrounding & separating each muscle

A.A. Connective Tissue2.2. DeepDeepa.a. EpimysiumEpimysium – a tough

outer coat of connective tissue surrounding the entire muscle.

b. Perimysiumb. Perimysium - several sheathed muslce fibers wraped in a coarse fibrous membrane.

A.A. Connective Tissue2.2. DeepDeepc. c. Fascicles – a bundle

of perimysium muscle fibers.

d. Endomysiumd. Endomysium - a delicate connective sheath around a single muscle fiber

3. 3. Tendons – cord like dense Tendons – cord like dense fibrous connective tissue.fibrous connective tissue.

a. Formed from the union of all three deep fascia

b. Connect muscle to muscle or muscle to bone

A.A. Connective Tissue

4. Aponeurosis 4. Aponeurosis – flat sheet of connective tissue that indirectly attaches muscles to bones, cartilage or other muscles.

A.A. Connective Tissue

AponeurosisAponeurosis

1.1. Each muscle Each muscle fiber fiber a.a.is a single, long, cylindrical is a single, long, cylindrical

muscle cell.muscle cell. • SarcolemmaSarcolemma is the plasma is the plasma

membrane of a muscle cell.membrane of a muscle cell.• SarcoplasmSarcoplasm is the cytoplasm of a is the cytoplasm of a

muscle cell. muscle cell. • Many mitochondria Many mitochondria • NucleiNuclei• Sarcoplasmic reticulumSarcoplasmic reticulum

B. Muscle FibersB. Muscle Fibers

B. Muscle FibersB. Muscle Fibers1. Each muscle 1. Each muscle fiberfiber

b. is wrapped in endomysium

1. Each muscle 1. Each muscle fiberfiberc. is a bundle of myofibrils myofibrils

which is made of a budle of myofilaments

2. FasciclesFascicles: a. a bundle

of muscle

fibersb. wrapped

in

perimysium

B. Muscle FibersB. Muscle Fibers

3. Myofibrils 3. Myofibrils a.a. made of made of thinthin and and thick thick

filamentsfilaments

B. Muscle FibersB. Muscle Fibers

3. Myofibrils 3. Myofibrils b.b. Thick filaments made Thick filaments made

up of up of the protein the protein myosinmyosin..

c. Thin filaments are c. Thin filaments are made up made up of the protein of the protein actinactin..

B. Muscle FibersB. Muscle Fibers

Thick filamentsThick filaments

Thin filamentsThin filaments

Tropomyosin and troponin are regulatory proteinsActin and myosin are contractile proteins.

3. Myofibril3. Myofibril d.d. Together, the thick Together, the thick

and and thin filaments make thin filaments make up the up the striationsstriations

B. Muscle FibersB. Muscle Fibers

B. Muscle FibersB. Muscle Fibers4. Sarcomeres- chains of tiny 4. Sarcomeres- chains of tiny

contractile myofibrils contractile myofibrils a. Contractile unit of a muscleb. Consists of overlapping

thick and thin filaments

SarcomereSarcomere

4. Sarcomere4. Sarcomerec. Muscle contractionc. Muscle contraction

results from thick and thin filaments sliding past one another.

B. Muscle FibersB. Muscle Fibers

1. Where the neuron and muscle fiber meet

C. Neuromuscular JunctionC. Neuromuscular Junction

2.The neuron and muscle fibers it controls make up a motor unitmotor unit (2-2000 fibers/unit)

MOTOR UNITMOTOR UNIT

3. When stimulated, all of the muscle fibers of a motor unit

C. Neuromuscular JunctionC. Neuromuscular Junction

contract all at once.

4. Anatomy Axon terminalAxon terminal – nerve end

C. Neuromuscular JunctionC. Neuromuscular Junction

• Produces a neurotransmitter - acetycholineacetycholine (Ach)

4. Anatomy Motor end plate –site on musclewith

C. Neuromuscular JunctionC. Neuromuscular Junction

acetycholine receptors Synaptic cleftSynaptic cleft - space between the nerve & motor end plate

Motor end plate

III. Skeletal Muscle III. Skeletal Muscle ContractionContractionA. Initiation events

1.1. nerve nerve impulse impulse

2.2. ACh ACh released released

3.3. Ach binds Ach binds to receptor to receptor on muscleon muscle

4.4. Enzyme Enzyme (Acetylcholi(Acetylcholine esterase ne esterase removes removes AChACh

III. Skeletal Muscle III. Skeletal Muscle ContractionContractionB. Action Potential

1.1. ACh causes ACh causes to Nato Na++ to to diffuse into celldiffuse into cell

2.2. If threshold is reached, If threshold is reached, action potential occursaction potential occurs- impulse travels along - impulse travels along membrane resulting in membrane resulting in contractioncontraction

III. Skeletal Muscle III. Skeletal Muscle ContractionContractionC. Sliding Filament TheoryC. Sliding Filament Theory

1.1.Action potential causes CaAction potential causes Ca++++ release release from S.Rfrom S.R

2.2.CaCa++++ binds to thin filament binds to thin filament 3.3.Thin filament rotates exposing Thin filament rotates exposing

binding site for myosin binding site for myosin 4.4.Myosin binds actin Myosin binds actin

» uses ATP to "rachet" once uses ATP to "rachet" once » releases, "and binds to next actinreleases, "and binds to next actin

Calcium is the "switch" that turns muscle "on and off" (contracting and relaxing).

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

D. How Neurotoxins Work D. How Neurotoxins Work 1.1.cobra toxin and curarecobra toxin and curare

– block Ach receptorsblock Ach receptors– cause flaccid paralysis, potentially fatal cause flaccid paralysis, potentially fatal

respiratory arrestrespiratory arrest2.2.nerve gas and insecticidesnerve gas and insecticides

• inhibit AchEinhibit AchE• cause potentially fatal paralytic convulsionscause potentially fatal paralytic convulsions

How a Nerve Gas Works

Normal Nerve Gas

Effect of Atropine on the Transmission of Acetylcholine in the

presence of a nerve agent

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

D. How Neurotoxins WorkD. How Neurotoxins Work3.3.Botulism toxin and curareBotulism toxin and curare

– block Ach releaseblock Ach release– cause flaccid paralysis, potentially fatal cause flaccid paralysis, potentially fatal

respiratory arrestrespiratory arrest4.4.Tetanus toxinTetanus toxin

• cause excessive Ach release from motor neuronscause excessive Ach release from motor neurons• causes potentially fatal paralytic convulsions causes potentially fatal paralytic convulsions

((““lock jawlock jaw””))

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

E. Rigor MortisE. Rigor Mortis• Ca++ pumps run out of ATP Ca++ pumps run out of ATP • Ca++ cannot be removedCa++ cannot be removed• continuous contraction continuous contraction • eventually tissues break down eventually tissues break down

IV. Energy Metabolism in IV. Energy Metabolism in Sk.Ms.Sk.Ms.

1.1.Most efficient use of glucoseMost efficient use of glucoseSources of glucose include blood Sources of glucose include blood glucose and stored glycogenglucose and stored glycogen

2.2.36ATP/glucose36ATP/glucose3.3.requires oxygenrequires oxygen4.4.occurs in mitochondriaoccurs in mitochondria

– Muscle cells have more Muscle cells have more mitochondria than any other cellmitochondria than any other cell

– Require a steady supply of ORequire a steady supply of O22

A. Aerobic RespirationA. Aerobic Respiration

B. B. Creatine-phosphagen Creatine-phosphagen systemsystem

1.1.During rest, muscles store During rest, muscles store energy as creatine energy as creatine phosphokinase (CPK or CK)phosphokinase (CPK or CK)

2.2.During intense exercise, During intense exercise, ATP is depleted first, then ATP is depleted first, then CK is used to convert ADP CK is used to convert ADP back to ATP back to ATP

C. C. Lactic Acid PathwayLactic Acid Pathway1.1.Anaerobic use of glucose Anaerobic use of glucose 2.2.2 ATP/ glucose2 ATP/ glucose3.3.Lactic acid produced as Lactic acid produced as

waste product waste product –– Oxygen Debt Oxygen Debt– Is toxic to tissueIs toxic to tissue– Can be recycled in liverCan be recycled in liver

V. Muscle TwitchV. Muscle Twitch--cycle of contraction and cycle of contraction and

relaxation relaxation

V. Muscle TwitchV. Muscle Twitch--cycle of contraction and cycle of contraction and

relaxation relaxationA. A. Reasons for varying degrees Reasons for varying degrees

1. The number of muscle fibers 1. The number of muscle fibers innervated by a single neuron innervated by a single neuron varies varies

2. Some motor units have lower 2. Some motor units have lower thresholds than othersthresholds than others

3. Muscle fibers differ functionally: 3. Muscle fibers differ functionally: fast twitch fast twitch –– slow twitch fibers slow twitch fibers

V. Muscle TwitchV. Muscle TwitchB. B. Fast vs Slow Twitch Fibers Fast vs Slow Twitch Fibers

1. Differ in 1. Differ in – How they make ATPHow they make ATP– Speed of ATP break downSpeed of ATP break down– Mitochondria contentMitochondria content– How fast they fatigueHow fast they fatigue

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers2. 2. Slow Twitch FibersSlow Twitch Fibers

– Smallest fibers Smallest fibers – Fatigue resistantFatigue resistant– Aerobic ATP productionAerobic ATP production– Many mitochondriaMany mitochondria– Slow contractionsSlow contractions– Example: uroanal musclesExample: uroanal muscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers2. Oxidative 2. Oxidative Fast Twitch Fast Twitch

Fibers FOGFibers FOG – Fatigue resistantFatigue resistant– Aerobic ATP productionAerobic ATP production– Many mitochondriaMany mitochondria– Fast contractionsFast contractions– Example: arm musclesExample: arm muscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers3. Glycolytic 3. Glycolytic Fast Twitch FibersFast Twitch Fibers

– Largest fibersLargest fibers– Fatigue easilyFatigue easily– Anaerobic ATP productionAnaerobic ATP production– Few mitochondriaFew mitochondria– Strong fast contractionsStrong fast contractions– Example: sprinter’s leg Example: sprinter’s leg

musclesmuscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers4. Muscles have combination of all 4. Muscles have combination of all

three fibersthree fibers – The number of each type varies from

individual to individual Endurance runningEndurance running - slow and fast - slow and fast oxidative oxidative fibersfibers SprintsSprints - fast oxidative fibers and some - fast oxidative fibers and some fast glycolytic fibersfast glycolytic fibers PowerliftingPowerlifting - fast glycolytic fibers & - fast glycolytic fibers & some some fast oxidativefast oxidative Old ageOld age - increase in slow oxidative - increase in slow oxidative fibersfibers

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers

4. Muscles have 4. Muscles have combination of all three combination of all three fibersfibers

– Training/conditioning can change the predominant fiber type in muscles

Anabolic steroidsAnabolic steroids– similar to testosterone similar to testosterone – large doses required for good effect large doses required for good effect – Side effects: Side effects: – overall - kidney and heart damage, overall - kidney and heart damage,

aggressivenessaggressiveness– females - sterility, facial hair, breast & females - sterility, facial hair, breast &

uterine atrophy uterine atrophy – males - baldness, atrophy of testismales - baldness, atrophy of testis

Sports injuries - RICE Sports injuries - RICE therapytherapy – Rest Rest

– Ice Ice – Compression Compression – Elevation Elevation

V. Skeletal MuscleV. Skeletal MuscleA. A. Muslce Attachments Muslce Attachments

1.1.Origin – attachment site of a muscle Origin – attachment site of a muscle or tendon to a bone that doesn’t or tendon to a bone that doesn’t move during contraction.move during contraction.

2.2.Insertion – is the attachment site of Insertion – is the attachment site of a muscle or tendon to a moving a muscle or tendon to a moving bone that moves during a bone that moves during a contraction. contraction. (usually distal)(usually distal)

V. Skeletal MuscleV. Skeletal MuscleB. B. Lever Systems Lever Systems

1.1.leverlever - rod that moves at the - rod that moves at the fulcrum (fixed point) fulcrum (fixed point)

2.2.fulcrumfulcrum typically the joint typically the joint moving moving

3.3.ResistanceResistance - gravity pulling - gravity pulling on body on body

4.4.EffortEffort - muscle contraction - muscle contraction

V. Skeletal MuscleV. Skeletal MuscleB. B. Lever Lever

Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – First classFirst class

levers - E F Rlevers - E F R

V. Skeletal MuscleV. Skeletal MuscleB. B. Lever Lever

Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – 2nd class2nd class

levers levers –– F R F R EELevers that operate @ a Levers that operate @ a

mechanical disadvantage are mechanical disadvantage are fast levers that require the fast levers that require the muscles to exert more force muscles to exert more force than the resistance to be than the resistance to be moved. moved.

V. Skeletal MuscleV. Skeletal MuscleB. B. Lever Lever

Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – 3rd class3rd class

levers levers –– F E F E RRmost commonmost commonLevers that operate @ a mechanical Levers that operate @ a mechanical

advantage allow a large load to be advantage allow a large load to be moved over a relatively small moved over a relatively small distance but require relatively little distance but require relatively little efforteffort

Interactions of Skeletal Muscles• Skeletal muscles work

together or in opposition• Muscles only pull (never

push)• As muscles shorten, the

insertion generally moves toward the origin

• Whatever a muscle (or group of muscles) does, another muscle (or group) “undoes”

V. Skeletal Muscle V. Skeletal Muscle InteractionsInteractions

C. C. Muscle Groups Muscle Groups 1.1.Many muscles are Many muscles are

required for any given required for any given movement movement – 1 muscle moves arm 1 muscle moves arm

up up – another muscle moves another muscle moves

arm down arm down

C. C. Muscle Groups Muscle Groups 2. Muscles work 2. Muscles work

togethertogether– AgonistAgonist > Prime move> Prime move > muscle that causes a > muscle that causes a

movementmovement– AntagonistAntagonist > opposes the muscle that > opposes the muscle that

stretches; regulates the muscle stretches; regulates the muscle contractioncontraction

Biceps – Agonist (prime mover)Triceps -- Antagonist Uncurl arm -- roles are reversed

Ex. Arm flexion

C. C. Muscle Groups Muscle Groups 2. Muscles work 2. Muscles work

togethertogether– Synergist Synergist >Assists the prime mover>Assists the prime mover– FixatorFixator >auxiliary muscles that steady a >auxiliary muscles that steady a

movement movement (immobilizes a bone or muscle’s (immobilizes a bone or muscle’s origin)origin)

The Belly of a muscle is called the Gaster!

Muscle Naming1. Location of the muscle ex. Anterior tibialis, ASIS, supra=above, infra=below,& sub=underneath

2. Size of the muscle ex. Maximus=largest, minimis=smallest, vastus=huge, longus=long, brevis=short, major=large, & minor=small

3. Direction of muscle fibers ex. Oblique (slant) Rectus (straight)

4. Number of origins ex. Triceps=3 origins or biceps=2 origins.

Muscle Naming5. Location of origin & insertion ex. Sternocleidomastoid

sterno=sternum, cleiodo=clavicle, mastoid=location on the temporal bone (mastiod bone)

6. Action of the muscle ex. Flexor= shortens angle b/w 2 bones, Extensor= increases the angle b/w 2 bones, Depressor = lowers, abductor= moves away from the midline, levator – lifts a structure

7. Shape of the muscle ex. Trapezius, Rhomboids, deltoid=triangular, Latissimus=wide, teres=round, trapezius=trapezoid, serratus=saw-tooth, & orbicularis=circular

Remember there are always exceptions to every rule & some muscle do not obey this naming rule.

Types of Body Movements• Flexion – movement that decreases the angle b/w 2

bones. Seen in hinge joints & ball & socket joints.

• Extension– movement that increases the angle b/w 2 bones. If extension is greater than 180o it’s called hyperextension.

• Abduction – Movement away from the midline of the body.

Types of Body Movements• Adduction – Movement toward the midline of the

body.

• Rotation – Movement where 1 bone moves around the longitudinal axis of another bone. Common movement in ball & socket joints.

• Circumduction – a combination movement of flexion, extension, abduction & adduction. The proximal end of a bone is stationary while the distal end moves in a circle. Common in ball & socket joints.

Types of Body Movements• Dorsiflexion – movement of foot decreases the

angle b/w the foot & the tibia. (upward movement of the foot – take your foot off the gas) Dorsiflexion in the foot is comparable to extension of the hand @ the wrist.

• Plantarflexion – movement of the foot to increase the angle b/w the foot & the tibia. (downward movement of the foot – mash on the gas) Plantarflexion of the foot is comparable to flexion of the hand @ the wrist.

Types of Body Movements

• Inversion – movement of the foot/ankle causing the sole of the foot to turn inward, (internal rotation).

• Eversion – movement of the foot/ankle causing the sole of the foot to turn outward, (external rotation)

• Pronation – movement causing the palm of the hand to turn down.

Types of Body Movements• Supination – movement causing the palm of the

hand to turn upward. (your hands are in supination when standing in anatomical position)

• Opposition – move the thumb to touch to tips of the opposite finger tips of the same hand.

• Protraction – movement of a body part anteriorly. forward motion (jutting out) of a limb.

• Retraction – movement of a body part posteriorly. backward motion of a limb.

Types of Body Movements• Elevation – upward movement of a body part.

• Depression – downward movement of a body part.

Types of Body Movements

Types of Body Movements

Types of Body Movements

Joint Motions

Arrangement of Muscle Fibers• Convergent – fascicles converge from a broad

origin to a single tendon insertion (e.g., pectoralis major)

• Circular – fascicles are arranged in concentric rings (e.g., orbicularis oris)

Arrangement of Muscle Fibers• Parallel – fibers run parallel to the long axis of

the muscle (e.g., sartorius)• Pennate (uni, bi, or multi)– short fascicles that

attach obliquely to a central tendon running the length of the muscle (e.g., rectus femoris)

Major Skeletal Muscles:

Anterior View

Figure 10.4b

Major Skeletal Muscles:

Posterior View

Figure 10.5b

Muscle Functions of the Head & Neck• Frontalis: Elevates the eyebrow; wrinkles

forehead horizontally.• Orbicularis Oculi: Closes the eyelids;

causes squinting, winking & blinking.• Orbicularis Oris: Draws lips together;

pucker & kissing muscle.• Zygomaticus: Raises corner of mouth

laterally as in smiling or laughing.• Buccinator: Compresses the cheek to

hold food during chewing, sucking in cheeks & allows to blow a horn.

Muscle Functions of the Head & Neck• Platysma: Depresses corner of mouth;

Frowning, pouting; tightens neck muscles when shaving.

• Masseter: Raises mandible & draws it forward= Chewing

• Occipitalis: Draws scalp backward.• Temporalis: Raises mandible. Covers

temporal bone in head.• Mentalis: wrinkles chin.• Sternocleidomastoid: Flexes head &

bends it laterally.

Muscles of the Scalp, Face, and Neck

Figure 10.6

Functions of Ventral Muscles of the Torso• Pectoralis Major: Adducts, flexes &

rotates the humerus medially. Moves arm forward across chest. (adduction)

• Pectoralis Minor: Draws scapula forward & downward.

• Serratus Anterior: draws scapula forward (protraction), upward rotation of the shoulder girdle.

• External Intercostals: chest muscles that elevate ribs & enlarge thorax during breathing.

Ventral Torso Muscles

Muscles of Respiration

Figure 10.10a

Functions of Ventral Muscles of the Torso• Internal Intercostals: Draw adjacent ribs together.• Diaphragm: Expands thorax; compresses

contents of abdominal cavity. (breathing)• Rectus Abdominus: The major muscles for spine

/trunk flexion (aka: your 6pack)• External Oblique: Slanted muscles of the abdomen

that flex & rotate the trunk (aka: you love handles)• Internal Oblique: flexion of the trunk, lateral

flexion (same side), rotation (same side) of the trunk.• Transverse Abdominis: compresses the

abdominal/pelvic cavity.

Muscles of the Abdominal Wall

Figure 10.11a

Functions of Dorsal Muscles of the Torso

• Trapezius: Hyperextension of head; adducts scapula; raises scapula. Allows you to shrug your shoulder & look up.

• Rhomboids Major & Minor: (beneath the trap) Small rectangular muscles that square the shoulders iow: Adducts & downward rotation of the shoulder.

• Latissimus Dorsi: A large muscle that adducts & extends the shoulder. (muscle originates from the lumbodorsal fascia)

• Teres Major & Minor: External rotation & horizontal abduction of the arm.

Functions of Dorsal Muscles of the Torso

• Erector Spinae: Primary back extensor, runs the length of the spine. Also causes lateral trunk flexion & rotation of the head, neck, shoulder, chest, & arm muscles. Made up of three columns on each side of the vertebrae – iliocostalis, longissimus, and spinalis. Lateral bending of the back is accomplished by unilateral contraction of these muscles

• Lumbar Aponeurosis: Sheet like tendinous expansion of a muscle.

• Levator Scapulae: Extension of the neck, downward rotation & elevation of the scapula. Synergist to the trapezius.

Dorsal Muscles of the Torso

Muscle Functions of the Upper ExtremityShoulder:•Anterior Deltoid: Abducts, flexes, internally rotates & horizontally adducts the arm. (deltoid is the antagonist to the trapezius)

•Medial Deltoid: Abducts the arm•Posterior Deltoid: Abducts, extends, externally rotates & horizontally abducts the arm.•Coracobrachialis: flexes & horizontally adducts the arm

Muscles Crossing the Shoulder

Figure 10.14a

Posterior view

Muscle Functions of the Upper ExtremityROTATOR CUFF: SITS• Supraspinatus; abducts the upper arm.

•Infraspinatus : Externally rotations the upper arm

•Teres Minor: Externally rotates the upper arm.

•Subscapularis : Internally rotations the upper arm.

Posterior view

Muscle Functions of the Upper Extremity

Muscles of the Arm•Biceps brachii: Flexion of the elbow & shoulder & supination of the forearm.•Brachialis: Flexes the elbow.•Pronator teres: Pronates the forearm.•Triceps brachii: Extends the elbow, adducts & extends the shoulder. (antagonist to biceps brachii)

•Anconeus: Elbow extension

Muscles Crossing the Shoulder

Anterior view Posterior view

Muscle Functions of the Upper ExtremityMuscles of the Arm•Supinator: supinates the forearm.•Flexor carpi radialis: Flexes & abducts the wrist.•Flexor carpi ulnaris: Flexes & adducts the wrist.•Extensor carpi radialis longus: Extends & adducts the wrist.•Extensor digitorum (longus & brevis): Extends the wrist.

Deep Dorsal view

Superficial Dorsal view

Muscle Functions of the Hand

There are three groups of intrinsic hand muscles:•The thenar eminence (ball of the thumb)•The hypothenar eminence (ball of the little finger) – both have a flexor, an abductor, and an opponens (opposer)muscle•The midpalm muscles, the lumbricals and interossei, extend the fingers•The interossei also abduct and adduct the fingers

Deep Dorsal view

Superficial Dorsal view

Muscle Functions of the Hand• Flexor digitorum Longus & brevis: flexes the

fingers.• Extensor digitorum longus & brevis: extends the

Fingers.• Extensor Pollicus Longus & Brevis: extends the

thumb.• Abductor Pollicus Longus & Brevis: abducts the

thumb.• Adductor Pollicus Longus & Brevis: adducts the

thumb.• Flexor Pollicus Longus & Brevis: flexes the thumb.

Muscle Functions of the Lower ExtremityMuscles of the Quadriceps (primary knee extensors)•Rectus femoris: hip flexion & knee extension•Vastus Lateralis & Medialis: knee extension.•Vastus Intermedius: knee extension

Other Muscles of the Thigh•Sartorius: flexion, external rotation & abduction of the hip; Flexion & internal rotation of the knee•Gracilis: Abduction, flexion & internal rotation of the hip; Internal rotation of the knee.•Adductor longus: Adduction, flexion & horizontal adduction of the hip. Allows you to grip a horse’s back w/your legs.•Adductor magnus: Adduction, flexion & horizontal adduction of the hip.

Muscles of the Pelvis & Femur

Muscle Functions of the Lower ExtremityMuscles of the Posterior Thigh:•Semimembranosus: Extension of the hip; Flexion & internal rotation of the knee.

•Semitendinosus: Extension & internal rotation of the hip; Flexion & internal rotation of the knee.

•Biceps Femoris: Extension of the hip; External rotation & flexion of the knee. •

Muscle Functions of the Lower ExtremityMuscles of the Posterior Thigh:•Gluteus Maximus: Extension, external rotation, horizontal abduction & adduction of the hip. Used to extend the hip when climbing stairs; forms the buttox.

•Gluteus Medius & Minimus: abduction, horizontal abduction & internal rotation of the hip.

Muscle Functions of the Lower ExtremityMuscles of the lower leg:•Tibialis Anterior: Dorsiflexion & inversion of the foot.•Extensor Digitorum Longus: Dorsiflexion & eversion of the foot.•Extensor Hallicus Longus: inversion & extension of the big toe.•Peroneus (Fibularis) Longus & Brevis: Plantarflexion & eversion of the foot.

Muscle Functions of the Lower ExtremityMuscles of the lower leg:•Soleus: plantarflexion of the foot. (lower calf muscle)•Gastrocnemius: Plantarflexion of the foot & flexion of the knee. (upper calf muscle)•Triceps Surae is the combination of the Soleus & the Gastronemius. Aka: toe dancer’s muscle.•Abductor Hallicus Longus & Brevis: abducts the big toe.•Adductor Hallicus Longus & Brevis: adducts the big toe.•Flexor Hallicus Longus & Brevis: flexes the big toe.

Muscles of the Lower Leg

Figure 10.22a

Muscle Functions of the Lower ExtremityMuscles of the lower leg:•Flexor digitorum Longus & brevis: flexes the toes.•Extensor digitorum longus & brevis: extends the toes.•Extensor Hallicus Longus & Brevis: extends the big toe.

Muscles of the Anterior Lower

Leg

Figure 10.21a

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References