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Title: Actions Of Skeletal Muscles
Description: Higher level Anatomy and Physiology course notes on actions of skeletal muscles. Includes origins, insertions, and actions of muscles.
Description: Higher level Anatomy and Physiology course notes on actions of skeletal muscles. Includes origins, insertions, and actions of muscles.
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Actions of Selected Skeletal Muscles
—skeletal muscles generally work across a joint to effect movement at the joint
—muscle pulls one articulating bone toward the other
—one of the bones remains more stationary = site of origin of muscle
—one of the bones moves more = site of insertion
—muscle belly is the fleshy part
—muscle belly does not overlie the part that it moves
—muscle belly is generally proximal to the part it moves
Muscles that Move the Head
sternocleidomastoid
origin: sternum and clavicle insertion: mastoid process of temporal bone
actions: acting together to extend head and elevate sternum
acting singly, rotate head to opposite side and flex laterally
splenius capitis
origin: ligamentum nuchae, cervical and thoracic spinous processes
insertion: occipital bone and mastoid process
action: acting together, extend head
acting singly, rotate head to same side
Muscles that Act on the Abdominal Wall
rectus abdominis
origin: pubic crest and symphysis
insertion: cartilage of ribs 5 – 7 and xiphoid process
action: flexes vertebral column
compresses abdomen to aid urination, defecation, forced exhalation
external oblique
origin: inferior 8 ribs
insertion: iliac crest and linea alba
action: compress abdomen, flex vertebral column,
acting unilaterally, laterally flex vertebral column and rotate
Muscles that Move the Pectoral Girdle
pectoralis minor
origin: second through fifth ribs (variable)
insertion: coracoid process of scapula
action: abducts scapula, rotates it downward
elevates ribs during forced exhalation
serratus anterior
origin: superior 8 or 9 ribs
insertion: vertebral (medial) border and inferior part of scapula
action: abducts scapula, rotates it upward
elevates ribs when scapula is stabilized
trapezius
origin: occipital bone, ligamentum nuchae, spines C7 & thoracic vertebrae
insertion: clavicle, acromion and spine of scapula
action: superior fibers elevate scapula
middle fibers adduct scapula
inferior fibers depress scapula
superior and inferior fibers rotate scapula upward
stabilizes scapula
levator scapulae
origin: C4 – C5 vertebrae
insertion: superior medial border of scapula
action: elevate scapula and rotate it down
rhomboid major
origin: spines of T2 – T5
insertion: medial border of scapula inferior to its spine
action: elevates and adducts scapula, rotates it down, stabilizes it
Muscles that Move the Humerus
pectoralis major
origin: head of clavicle, sternum , costal cartilages, 1st to 7th ribs(variable)
insertion: greater tubercle and intertubercular sulcus of humerus
action: adducts and medially rotates arm at shoulder joint
clavicular head alone flexes arm
sternocostal head extends arm at shoulder joint
latissimus dorsi
origin: spines of T6 – T12, lumbar vertebrae, iliac crest
insertion: intertubercular sulcus of humerus
action: extends, adducts, medially rotates arm at shoulder joint
deltoid
origin: acromial extremity of clavicle, acromion and spine of scapula
insertion: deltoid tuberosity of humerus
action: lateral fibers abduct arm at shoulder joint
anterior fibers flex and medially rotate
posterior fibers extend and laterally rotate
subscapularis
origin: subscapular fossa of scapula
insertion: lesser tubercle of humerus
action: medially rotates arm at shoulder joint
supraspinatus
origin: supraspinous fossa of scapula
insertion: greater tubercle of humerus
action: assists deltoid in abducting arm at shoulder joint
infraspinatus
infraspinous fossa of scapula
insertion: greater tubercle of humerus
action: laterally rotates and adducts arm at shoulder joint
teres major
origin: inferior angle of scapula
insertion: intertubercular sulcus of humerus
action: extends arm at shoulder, assists in adduction and medial rotation
teres minor
origin: inferior lateral border of scapula
insertion: greater tubercle of humerus
action: laterally rotates, extends, adducts arm at shoulder joint
Muscles that Move Radius & Ulna
Forearm Flexors
biceps brachii
origins: long head from supraglenoid tubercle of scapula
short head from coracoid process of scapula
insertion: radial tuberosity of radius, bicipital aponeurosis
action: flexes forearm at elbow joint
brachialis
origin: distal, anterior surface of humerus
insertion: ulnar tuberosity and coronoid process of ulna
action: flexes forearm at elbow joint
brachioradialis
origin: lateral border of distal humerus
insertion: superior to styloid process of radius
action: flexes forearm at elbow joint
pronates and supinates forearm at radioulnar joint
Forearm Extensors
triceps brachii
origin: long head from infraglenoid tubercle
lateral head from lateral and posterior humerus
medial head from posterior surface of humerus inferior to groove for
radial nerve
insertion: olecranon of ulna
action: extends forearm at elbow
Muscles that Move Wrist, Hand, Thumb, Fingers
superficial anterior compartment (flexor) of forearm
flexor carpi radialis
palmaris lngus
flexor carpi ulnaris
flexor digitorum superficialis
superficial posterior compartment (extensor) of forearm
extensor carpi radialis brevis
extensor carpi ulnaris
extensor digitorum
Muscles that Move the Vertebral Column
erector spinae group (not seen on models)
Muscles that Move the Femur
psoas major and iliacus (iliopsoas)
origin: psoas from transverse processes of lumbar vertebrae
iliacus from ilium
insertion: lesser trochanter of femur
action: flex thigh at hip and rotate thigh: flex trunk at hip
gluteus maximus
origin: iliac crest, sacrum, coccyx, aponeurosis of sacrospinalis
insertion: iliotibial tract and lateral part of linea aspera on femur
action: extends thigh at hip joint and laterally rotates thigh
gluteus medius
origin: ilium
insertion: greater trochanter
action: abducts femur at hip joint and medially rotates thigh
gluteus minimus (not seen on models)
origin: ilium
insertion: greater trochanter
action: abducts femur at hip joint and medially rotates thigh
tensor fasciae latae
origin: iliac crest
insertion: tibia by way of iliotibial tract
action: flexes and abducts thigh at hip
piriformis
origin: anterior sacrum
insertion: superior border of greater trochanter of femur
action: laterally rotates and abducts thigh at hip joint
adductor longus
origin: pubic crest and symphysis
insertion: linea aspera of femur
action: adduct, flex, medially rotate thigh
adductor magnus
origin: inferior ramus of pubis and ischium to ischial tuberosity
insertion: linea aspera of femur
action: adduct and medially rotate thigh at hip
anterior part flexes, posterior part extends thigh
Muscles that Act on Femur and Tibia and Fibula
gracilis
origin: pubic symphysis and a
insertion: medial surface of tibia
action: adducts thigh at hip, medially rotates thigh, flexes leg at knee
Muscles that Act on the Leg
Leg Extensors
quadriceps femoris
quadriceps femoris
rectus femoris
origin: anterior inferior iliac spine
vastus lateralis
origin: greater trochanter and linea aspera of femur
vastus medialis
origin: linea aspera of femur
vastus intermedius deep to rectus femoris
origin: anterior and lateral surfaces of body of femur
common insertion: patella via quadriceps tendon, continuing
inferiorly to tibial tuberosity via patellar tendon
action: all 4 heads extend leg at knee joint
rectus femoris alone flexes thigh at hip joint
sartorius
origin: anterior superior iliac spine
insertion: medial surface of body of tibia
action: flex leg at knee; flex, abduct, laterally rotate thigh at hip
Leg Flexors
hamstrings
biceps femoris
origin: long head from ischial tuberosity
short head from linea aspera of femur
insertions: head of fibia and lateral condyle of tibia
action: flex leg at knee and extend thigh at hip
semitendinosus
origin: ischial tuberosity
insertion: proximal medial shaft of tibia
action: flex leg at knee and extend thigh at hip
semimembranosus
origin: ischial tuberosity
insertion: medial condyle of tibia
action: flex leg at knee and extend thigh at hip
Muscles that Move Foot and Toes
anterior compartment
tibialis anterior
origin: lateral condyle and body of tibia and interosseus membrane
insertion: first metatarsal and cuneiform (medial)
action: dorsiflexes foot at ankle
inverts foot at intertarsal joints
extensor digitorum longus
origin: lateral condyle of tibia, anterior surface of fibula, interosseus
membrane
insertion: middle and distal phalanges of toes 2 – 5
action: dorsiflexes foot at ankle, extends phalanges at multiple joints
lateral compartment
fibularis longus
origin: head and body of fibula, lateral condyle of tibia
insertion: first metatarsal and cneiform
action: plantar flex foot at ankle, evert foot at intertarsals
Muscles that Move Foot and Toes
posterior compartment
gastrocnemius
origin: lateral and medial condyle of femur and capsule of knee
insertion: calcaneus by way of calcaneal tendon
action: plantar flexes foot at ankle joint
flexes leg at knee joint
soleus
origin: head of fibula and medial border of tibia
insertion: calcaneus by way of calcaneal tendon
action: plantar flexes foot at ankle joint
Title: Actions Of Skeletal Muscles
Description: Higher level Anatomy and Physiology course notes on actions of skeletal muscles. Includes origins, insertions, and actions of muscles.
Description: Higher level Anatomy and Physiology course notes on actions of skeletal muscles. Includes origins, insertions, and actions of muscles.