MUSCULAR SYSTEM
Chapter 8
WHAT DO MUSCLES DO?
 All movements require muscles, which are organs
that use chemical energy to contract.
 Walking, breathing, eating, sneezing, all require muscles
 Provide muscle tone
 Propel body fluids and food
 Generate heart beats
 Distribute heat
 Maintain posture
T YPES OF MUSCLE
 Skeletal (majority of this chapter)
 Attaches to bone and consciously controlled
 Smooth-hollow internal organs, irises, blood vessels
 Cardiac-heart
RULES OF MUSCULAR ACTIVIT Y
 1 . Muscles get shorter as they contract
 2. Muscles cross at least one joint
 3. Muscles have an origin and insertion
 Origin: immovable end of muscle
 Insertion: movable end
 4. When a muscle contracts, its insertion is pulled toward the
origin.
INTERACTIONS OF MUSCLES
 Skeletal muscles function in groups.
 Prime Mover: the muscle doing the majority of the work during a
movement
 Synergists: helper muscles
 Antagonists: opposing muscles
MUSCULAR MOVEMENTS
Insertion
(moveable end)
Origin
(immovable end)
MUSCULAR MOVEMENTS
 Flexion: angle between joint is decreased
MUSCULAR MOVEMENTS
 Extension: angle of joint is increased
 Hyperextension: extension beyond normal anatomical position
 Abduction: moving a part away from midline
 Adduction: moving a part toward midline
 Rotation: moving a part around an axis
 You will look up the rest of the muscle movements for
homework tonight (P. 167 -170 in book)
MAJOR SKELETAL MUSCLES
 Named according to:
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1.
2.
3.
4.
5.
Size (pectoralis major)
Shape (orbicularis oris)
Location (tibialis anterior)
Movement (extensor digitorum)
Number of attachments (biceps brachii)
 About 650 muscles in the human body
MAJOR SKELETAL MUSCLES
MUSCLES OF FACIAL EXPRESSION
 Epicranius-raises eyebrow
 Orbicularis Oculi-closes eye
 Orbicularis Oris-closes and protrudes lips
 Buccinator-puckers cheeck
 Zygomaticus-raises corner of mouth (Smile)
 Platysma-draws angle of mouth downward
MUSCLES OF MASTICATION
 (Chewing)
 Masseter: elevates mandible
 Temporalis: elevates mandible
MUSCLES THAT MOVE HEAD
 Sternocleidomastoid: pulls head to one side, toward chest, or
raises sternum
 Splenius capitis: rotates head, bends head to one side, or
brings head to upright position
 Semispinalis capitis: extends head, bends head to one side,
rotates head
MUSCLES THAT MOVE HEAD
MUSCLES THAT MOVE ARM
BACK, CHEST MUSCLES
 Trapezius: rotates scapula, raises arm, raises scapula, pulls
scapula medially, pulls shoulder down
 Deltoid: abducts arm, extends/flexes humerus
 Latissimus Dorsi: extends/adducts arm, rotates arm inwardly,
pulls shoulder down
 Rhomboid Major: raises and adducts scapulae
 Levator Scapulae: elevates scapulae
 Pectoralis Minor: pulls scapula anteriorly and down
 Pectoralis Major: pulls arm anteriorly and across chest,
rotates humerus, adducts arm
ABDOMINALS
 External Oblique
 Rectus Abdominus
 Transversus Abdominus
 Internal Oblique
MUSCLES THAT MOVE FOREARM
MOVE FOREARM
 Biceps Brachii: flexes forearm at elbow and rotates hand
laterally
 Brachioradialis: flexes forearm at elbow
 Triceps Brachii: extends forearm at elbow
MOVE HAND
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Flexor Carpi Radialis: flexes and abducts wrist
Palmaris longus: flexes wrist
Flexor Carpi Ulnaris: flexes and adducts wrist
Extensor Carpi Ulnaris: extends and adducts wrist
Extensor Digitorum: extends fingers
Extensor Carpi radialis brevis: extends wrist and abducts hand
THIGH
THIGH MUSCLES
 Gluteus maximus: extends thigh
 Gluteus medius: abducts and rotates thigh medially
 Sartorius: flexes leg/thigh, abducts thigh, rotates thigh
laterally, rotates leg medially
 Semitendinosus: flexes leg, extends thigh
 Semimembranosus: flexes leg, extends thigh
 Quadriceps femoris (4 parts): extends leg at knee
MUSCLES THAT MOVE FOOT
MUSCLES THAT MOVE FOOT
 Tibialis anterior: dorsiflexion and inversion of foot
 Extensor digitorum longus: dorsiflexion and eversion of foot;
extension of foot
 Gastrocnemius: plantar flexion of foot and flexion of leg at
knee
 Flexor digitorum longus: plantar flexion and inversion of foot,
flexion of four lateral toes
 Tibialis posterior: plantar flexion and inversion of foot