THE MUSCULAR SYSTEMTHE MUSCULAR SYSTEM

GeneralitiesGeneralities

• Muscles are created to CONTRACT• All muscle cells are elongated… that is why

they are called FIBERS

• Muscles are created to CONTRACT• All muscle cells are elongated… that is why

they are called FIBERS

Neuromuscular JunctionNeuromuscular Junction

• This is the junction between the sarcolemma of a muscle cell and the axonal terminal of a neuron

• Synaptic cleft– The space between

the end of the axonal terminal and the sarcolemma

• This is the junction between the sarcolemma of a muscle cell and the axonal terminal of a neuron

• Synaptic cleft– The space between

the end of the axonal terminal and the sarcolemma

Head MusclesHead Muscles

FacialFacial

FrontalisFrontalis

• Covers frontal bone• Raises your eyebrows• Wrinkles your

forehead

• Covers frontal bone• Raises your eyebrows• Wrinkles your

forehead

Orbicularis oculiOrbicularis oculi

• Encircles the eyes• allows one to wink

and close his eyes

• Encircles the eyes• allows one to wink

and close his eyes

BuccinatorBuccinator

• Runs horizontally across the cheek

• For whistling

• Runs horizontally across the cheek

• For whistling

ZygomaticusZygomaticus

• Smiling muscle• Smiling muscle

Head MusclesHead Muscles

ChewingChewing

MasseterMasseter

• Closes the jaw by elevating the mandible

• Closes the jaw by elevating the mandible

TemporalisTemporalis

• Overlies the temporal bone

• Acts as the synergist of masseter in closing the jaw

• Overlies the temporal bone

• Acts as the synergist of masseter in closing the jaw

Neck and Trunk MusclesNeck and Trunk Muscles

AnteriorAnterior

SternocleidomastoidSternocleidomastoid

• “prayer muscle”• Contraction of both

sides flexes neck as if bowing in prayer

• Contraction of one side would turn the head

• “prayer muscle”• Contraction of both

sides flexes neck as if bowing in prayer

• Contraction of one side would turn the head

Pectoralis MajorPectoralis Major

• Forms anterior wall of axilla and upper part of the chest

• Adducts and flexes the arm

• Forms anterior wall of axilla and upper part of the chest

• Adducts and flexes the arm

Abdominal Girdle MusclesAbdominal Girdle Muscles

• Rectus abdominis– Flexion of vertebral column

• External Oblique– Rotates and bends the

trunk

• Internal Oblique– Rotates and bends the

trunks

• Transversus abdominis– Compresses abdominal

contents

• Rectus abdominis– Flexion of vertebral column

• External Oblique– Rotates and bends the

trunk

• Internal Oblique– Rotates and bends the

trunks

• Transversus abdominis– Compresses abdominal

contents

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Neck and Trunk MusclesNeck and Trunk Muscles

PosteriorPosterior

TrapeziusTrapezius

• Kite-like shape• Extends the head• Elevates, depress,

adduct and stabilize the scapula

• Kite-like shape• Extends the head• Elevates, depress,

adduct and stabilize the scapula

Latissimus DorsiLatissimus Dorsi

• Covers the lower back

• Extends and adducts the humerus

• Used when arms are brought down in swimming or striking a downward blow

• Covers the lower back

• Extends and adducts the humerus

• Used when arms are brought down in swimming or striking a downward blow

Erector SpinaeErector Spinae

• Prime mover of back extension

• Composed of longissimus, iliocostalis and spinalis

• Controls the act of bending over at the waist

• Prime mover of back extension

• Composed of longissimus, iliocostalis and spinalis

• Controls the act of bending over at the waist

DeltoidDeltoid

• Forms the rounded shape of the shoulder

• Prime movers of arm abduction

• Forms the rounded shape of the shoulder

• Prime movers of arm abduction

Muscles of the Upper LimbMuscles of the Upper Limb

Biceps BrachiiBiceps Brachii

• Bulges upon flexion of the elbow

• Acts to flex and supinate the forearm

• Bulges upon flexion of the elbow

• Acts to flex and supinate the forearm

Triceps BrachiiTriceps Brachii

• Antagonist of the biceps

• Prime mover of elbow extension

• Used in delivering a straight punch

• Antagonist of the biceps

• Prime mover of elbow extension

• Used in delivering a straight punch

Muscles of the Lower LimbMuscles of the Lower Limb

Gluteus MaximusGluteus Maximus

• Forms most of buttock flesh

• Powerful hip extensor when walking, jumping and climbing the stairs

• Forms most of buttock flesh

• Powerful hip extensor when walking, jumping and climbing the stairs

Gluteus MediusGluteus Medius

• Used mainly for giving intramuscular injections

• It is a hip abductor and important in steadying the pelvis when walking

• Used mainly for giving intramuscular injections

• It is a hip abductor and important in steadying the pelvis when walking

IliopsoasIliopsoas

• Prime mover of hip flexion

• Prime mover of hip flexion

SartoriusSartorius

• Thin and strap like• used when crossing

the legs• runs obliquely across

the anterior aspect of the thigh

• Thin and strap like• used when crossing

the legs• runs obliquely across

the anterior aspect of the thigh

Quadriceps GroupQuadriceps Group

• Found at the anterior thigh

• Acts to extend the knee and flex the hip

• Parts:– Rectus femoris– Vastus medialis– Vastus lateralis

• Found at the anterior thigh

• Acts to extend the knee and flex the hip

• Parts:– Rectus femoris– Vastus medialis– Vastus lateralis

Hamstring GroupHamstring Group

• Found at the posterior thigh

• For knee flexion• Formed by the:

– Biceps femoris– Semi-membranosus– Semi-tendinosus

• Found at the posterior thigh

• For knee flexion• Formed by the:

– Biceps femoris– Semi-membranosus– Semi-tendinosus

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Tibialis AnteriorTibialis Anterior

• Found on the anterior leg

• Acts on dorsiflexion and inverts the foot

• Found on the anterior leg

• Acts on dorsiflexion and inverts the foot

Peroneus MusclePeroneus Muscle

• Found at the lateral area of the leg

• Group helps the gastrocnemius in plantar flexion

• Everts the foot

• Found at the lateral area of the leg

• Group helps the gastrocnemius in plantar flexion

• Everts the foot

GastrocnemiusGastrocnemius

• Curved over the posterior leg forming the “calves”

• Prime mover for plantar flexion (lifts the heels)

• Curved over the posterior leg forming the “calves”

• Prime mover for plantar flexion (lifts the heels)

Fig. 7.1Fig. 7.1

Fig. 7.4Fig. 7.4

Fig. 7.6Fig. 7.6

Fig. 7.11Fig. 7.11

Fig. 7.12Fig. 7.12

Fig. 7.13aFig. 7.13a

Fig. 7.13bFig. 7.13b

Fig. 7.15Fig. 7.15

Fig. 7.16Fig. 7.16

Fig. 7.17Fig. 7.17

Fig. 7.18Fig. 7.18

Fig. 7.19Fig. 7.19

Fig. 7.21abFig. 7.21ab

Fig. 7.21cFig. 7.21c

Fig. 7.22Fig. 7.22

Fig. 7.23Fig. 7.23

Fig. 7.25abFig. 7.25ab

Fig. 7.25cFig. 7.25c

Fig. 7.27abFig. 7.27ab

Fig. 7.27cFig. 7.27c

Fig. 7.24Fig. 7.24

Fig. 7.26Fig. 7.26