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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R
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
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