The Muscular System

Pictures

Bone

Perimysium

Endomysium(between individualmuscle fibers)

Muscle fiber

Fascicle(wrapped by perimysium)

Epimysium

Tendon

Epimysium

Muscle fiberin middle ofa fascicle

Blood vessel

Perimysium

Endomysium

Fascicle(a)

(b)

Myofibril

Myofibrils

Triad:

Tubules ofthe SR

Sarcolemma

Sarcolemma

Mitochondria

I band I bandA bandH zone Z lineZ line

Part of a skeletalmuscle fiber (cell)

• T tubule• Terminal

cisternaeof the SR (2)

M line

Myofibrils

Nucleus

Light I bandDark A band

Sarcolemma

Mitochondrion

Myofibril

Features of a Sarcomere

I band I bandA bandSarcomere

H zoneThin (actin)filament

Thick (myosin)filament

Z line Z line

M line

Z line Z lineM lineSarcomere

Thin (actin)filament

Thick(myosin)filament

Elastic (titin)filaments

Flexible hinge region

Tail

Tropomyosin Troponin ActinMyosin head

ATP-bindingsite

Heads Active sitesfor myosinattachment

Actinsubunits

Actin-binding sites

Thick filamentEach thick filament consists of manymyosin molecules whose heads protrude at opposite ends of the filament.

Thin filamentA thin filament consists of two strandsof actin subunits twisted into a helix plus two types of regulatory proteins(troponin and tropomyosin).

Thin filamentThick filament

In the center of the sarcomere, the thickfilaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap.

Longitudinal section of filamentswithin one sarcomere of a myofibril

Portion of a thick filamentPortion of a thin filament

Myosin molecule Actin subunits

I

Fully relaxed sarcomere of a muscle fiber

Fully contracted sarcomere of a muscle fiber

IAZ ZH

I IAZ Z

1

2

1

Actin

Cross bridge formation.

Cocking of myosin head. The power (working) stroke.

Cross bridge detachment.

Ca2+

Myosincross bridge

Thick filament

Thin filament

ADP

Myosin

Pi

ATPhydrolysis

ATP

ATP

24

3

ADPPi

ADPPi

Actin

Cross bridge formation.

Ca2+

Myosincross bridge

Thick filament

Thin filament

ADP

Myosin

Pi

1

The power (working) stroke.

ADPPi

2

Cross bridge detachment.

ATP

3

Cocking of myosin head.

ATPhydrolysis

ADPPi

4

1

Actin

Cross bridge formation.

Cocking of myosin head. The power (working) stroke.

Cross bridge detachment.

Ca2+

Myosincross bridge

Thick filament

Thin filament

ADP

Myosin

Pi

ATPhydrolysis

ATP

ATP

24

3

ADPPi

ADPPi

Latentperiod

Singlestimulus

Period ofcontraction

Period ofrelaxation

Myogram showing the three phases of an isometric twitch

Coupled reaction of creatinephosphate (CP) and ADP

Energy source: CP

Direct phosphorylation

Oxygen use: NoneProducts: 1 ATP per CP, creatineDuration of energy provision:15 seconds

Creatinekinase

ADPCP

Creatine ATP

Shoulder

Arm

Forearm

Pelvis/thigh

Thigh

Leg

Head Facial

Neck

Thorax

Abdomen

Thigh

Leg

TrapeziusDeltoid

Triceps brachiiBiceps brachiiBrachialis

Pronator teresBrachioradialisFlexor carpi radialisPalmaris longus

IliopsoasPectineus

Rectus femorisVastus lateralisVastus medialis

Fibularis longusExtensor digitorum longusTibialis anterior

Temporalis Epicranius, frontal bellyOrbicularis oculiZygomaticusOrbicularis oris

Sternohyoid

Sternocleidomastoid

Pectoralis major

Pectoralis minorSerratus anterior

Intercostals

External oblique

Rectus abdominisInternal obliqueTransversus abdominis

SartoriusTensor fasciae latae

Adductor longusGracilis

GastrocnemiusSoleus

Masseter

Platysma

ArmTriceps brachii

Brachialis

ForearmBrachioradialis

Extensor carpiulnaris Extensor digitorum

Iliotibial tract

LegGastrocnemius

SoleusFibularis longus

NeckEpicranius, occipital bellySternocleidomastoidTrapezius

Shoulder

HipGluteus mediusGluteus maximus

Thigh

Biceps femoris

Adductor magnus

SemitendinosusSemimembranosus

Latissimus dorsiRhomboid major

InfraspinatusDeltoid

Teres major

Flexor carpi ulnaris

Extensor carpiradialis longus

Calcaneal(Achilles) tendon

Hamstrings:

Corrugatorsupercilii

Orbicularis oculiLevator labiisuperiorisZygomaticusminor and majorBuccinator

RisoriusOrbicularis oris

MentalisDepressor labii inferioris

Depressor anguli orisPlatysma

Galeaaponeurotica

Frontal belly

Occipitalbelly

Temporalis

MasseterSternocleidomastoidTrapezius

Splenius capitis

Epicranius

Tongue Styloid processStyloglossusHyoglossus

StylohyoidHyoid bone

Thyrohyoid

GenioglossusMandibularsymphysis

GeniohyoidThyroid cartilage

MylohyoidAnteriorbellyPosteriorbelly

Stylohyoid (cut)ThyrohyoidThyroid cartilageof the larynx

Median raphe

Sternothyroid

StylohyoidHyoid boneOmohyoid(superior belly)SternohyoidSternocleido-mastoid Omohyoid(inferior belly)

Digastric

Thyroid gland

Mastoid processof temporal bone

SemispinaliscapitisSemispinaliscervicis

Multifidus

Quadratuslumborum

Semispinalisthoracis

Longissimus capitisIliocostalis cervicis

Longissimus cervicis

Iliocostalis thoracis

Longissimus thoracisSpinalis thoracis

Iliocostalis lumborum

External oblique

IliocostalisLongissimusErector

spinae Spinalis

Ligamentumnuchae

Externalintercostal

Internalintercostal

Foramen foresophagusCostal cartilage

Lumbarvertebra

Xiphoid process of sternum

Diaphragm

Quadratuslumborum Psoas major

Foramen for inferiorvena cava

Centraltendon ofdiaphragm

Foramenfor aorta

12th rib

Transversus abdominisInternal obliqueExternal oblique

Aponeurosis of theexternal oblique

Pectoralis major

Linea alba

TendinousintersectionRectusabdominis

Inguinal ligament(formed by free inferior border of the external oblique aponeurosis)

Serratus anterior

Transversusabdominis

Inguinalligament

Lumbarfascia

Lumbarfascia

Internaloblique

Pubictubercle

Rectusabdominis

Externaloblique

IIiac crest

SubclaviusClavicle

SubscapularisPectoralis minor

Coracobrachialis

Serratus anterior

Humerus

Sternocleido-mastoid

DeltoidPectoralismajor Sternum

Biceps brachii

Trapezius

LevatorscapulaeSupraspinatusClavicleSpine ofscapula InfraspinatusTeres minor

Humerus

Deltoid

Teres major

Latissimusdorsi

RhomboidminorRhomboidmajor

Biceps brachii

Tendon of biceps brachiiPronator teresBrachioradialis

Extensor carpi radialis longus

Flexor pollicis longus

Pronator quadratusFlexor retinaculum

Medial head oftriceps brachii

Medial epicondyleof humerus

Flexor carpi radialis

Palmar aponeurosis

Superficial transverseligament of palm

Palmaris longusFlexor carpi ulnaris

Flexor digitorumsuperficialis

Supinator

Tendon of flexorcarpi ulnaris (cut)

Tendon of flexordigitorum profundus

Flexor pollicis longus

Thenar muscles of thumb

Tendon of flexorpollicis longus

Lumbricals

Tendon of flexor digitorumsuperficialis (cut)

Pronator quadratus

Flexor digitorumprofundus

Insertion oftriceps brachii

Anconeus

Flexor carpiulnaris

Extensor carpiulnaris

Extensor digitiminimi

Extensor indicisTendons of extensor carpiradialis brevis and longus

Extensorexpansion

Extensor pollicislongusExtensor pollicisbrevisAbductorpollicis longusExtensor digitorumExtensor carpiradialis brevisExtensor carpiradialis longus

Brachioradialis

Tendons ofextensordigitorum

Psoas minorIliac crest

Psoas majorIliopsoas

12th ribQuadratus lumborum

IliacusAnterior superior iliac spine

Tensor fasciae lataePectineusSartoriusQuadriceps femoris• Rectus femoris • Vastus lateralis• Vastus medialis

Adductor magnus

PatellaPatellar ligament

Tendon of quadriceps femoris

12th thoracic vertebra

5th lumbar vertebra

Adductor longusGracilis

Gluteus medius

Gluteus maximus

Adductor magnusGracilisIliotibial tract

Long head

SemitendinosusSemimembranosus

Short headBicepsfemoris Hamstrings

PatellaHead of fibulaGastrocnemiusSoleusFibularis longusExtensor digitorum longusTibialis anteriorExtensor hallucis longusFibularis tertius

Fibularis brevisFlexor hallucis longus

Fibular retinaculumLateral malleolus

Superior and inferior extensorretinacula

Extensor digitorum brevis

5th metatarsal

Extensor hallucis brevis

Gastrocnemiusmedial head (cut)

Flexor digitorumlongus

Tendon of tibialisposterior Medial malleolusCalcaneal tendon (cut)

Calcaneus

Fibularis brevis

Flexor hallucis longus

Fibularis longusFibulaTibialis posteriorSoleus (cut)Popliteus

Gastrocnemiuslateral head (cut)

Plantaris (cut)