Muscle ReviewChapters 9 & 10

Description: covers forehead and dome of skull – no boney attachments

Origin: galea aponeurotica Insertion: skin of the eyebrows, root of nose Action: raises eyebrows wrinkles forehead

skin horizontally

Epicranius - Frontal belly

Description: overlies posterior occiput; be pulling on the galea, fixes origin of frontalis

Origin: occipital and temporal bones Insertion: galea aponeurotica Action: fixes aponeurosis and pulls scalp

posteriorly

Epicranius – occipital belly

Description: fan-shaped muscle that covers part of the temporal, frontal and parietal bones

Origin: temporal fossa Insertion: coronoid process of mandible via

tendon Action: Closes jaw, elevates and retract

mandible, maintains jaw position at rest

Temporalis

Description: thin, tripartite sphincter muscle of eyelid, surround rim of orbit

Origin: frontal and maxillary bones and ligaments around orbit

Insertion: tissue of eyelid Action: protects eye from intense light and

injury, blinking, squinting, draws eyebrows inferiorly

Orbicularis Oculi

Description: Powerful muscle that covers lateral aspect of mandibular ramus

Origin: zygomatic arch and maxilla Insertion: angle of ramus of mandible Action: prime mover of jaw closers: elevates

mandible

Masseter

Description: muscle pair extending diagonally from cheekbone to corner of mouth

Origin: zygomatic bone Insertion: skin and muscle at corner of

mouth Action: raises lateral corners of mouth

upward (smiling muscle)

Zygomaticus

Description: Complicated multilayered muscle of the lips with fibers that run in many different directions (most run circularly)

Origin: indirectly from maxilla and mandible, fibers blend with fibers of other facial muscles

Insertion: encircles mouth Action: closes lips, purses and protrudes lips

(kissing and whistling muscle)

Orbicularis Oris

Description: Unpaired, thin sheet-like superficial neck muscle, plays a role in facial expression

Origin: fascia of chest (over pectoral and deltoid)

Insertion: lower margin of mandible and skin at corner of mouth

Action: downward sag of mouth, tenses skin of neck for shaving

Platysma

Description: most medial muscle of the neck: thin, superficial except inferiorly, where cover by the sternocleidomastoid

Origin: manubrium and medial end of clavicle

Insertion: lower margin of hyoid bone Action: depresses larynx and hyoid bone if

mandible is fixed may also flex skull

Sternohyoid

Description: two-headed muscle loacted deep to the platysma on anterolateral surface of neck

Origin: manubrium and medial portion of clavicle

Insertion: mastoid process of temporal bone Action: primer mover of head flexion; actin

g alone can rotate head toward shoulder on opposite side, tilts head laterally

Sternocleidomastoid

Description: Flat, thin muscle directly beneath and obscured by pectoralis major

Origin: anterior surface of ribs 3-5 or (2-4) Insertion: coracoid process of scapula Action: With ribs fixed, draws scapula

forward and downward, with scapula fixed draws rib cage superiorly

Pectoralis minor

Description: large, fan-shaped muscle covering upper portion of chest, divided into clavicular and sternal parts

Origin: sternal end of clavicle, cartilage of ribs 1-6 (or 7) and aponeurosis of external oblique

Insertion: greater tubercle of humerus Action: prime mover of arm flexion, rotates

arm medially, assist in climbing, throwing, pushing and forced inspiration

Pectoralis major

Description: fan-shaped muscle; lies deep to the scapula, beneath and inferior to pectoral muscles on lateral rib cage

Origin: ribs 1-8 (or 9) Insertion: entire anterior surface of

vertebral border of scapula Action: prime mover to protract and hold

scapula against chest wall; abduction and raising arm, pushing punching (boxer’s muscle)

Serratus Anterior

Description: partially covered by deltoid and trapezius, named for its scapular location: rotator cuff muscle

Origin: infraspinatus fossa of scapula Insertion: greater tubercle of humerus

posterior to supraspinatus Action: helps to hold the head of humerus in

the glenoid cavity, stabilizing the joint,rotates humerus laterally

Infraspinatus

Description: Thick, rounded muscle located inferior to teres minor

Origin: postrior surface of scapula at inferior angle

Insertion: intertubercular sulcus of humerus; insertion tendon is fused with latisimus dorsi

Action: posteromedially extends, medially rotates and adducts humerus; synergist of lats

Teres Major

Description: two rectangular muscles lying deep to the trapezius and inferior to levator scapulae

Origin: spinous processes of C7 and T5 Insertion: medial border of scapula Action: retract scapula “squaring the

shoulders” rotate glenoid cavity of scapula downward (paddling a canoe) stabilizing shoulder

Rhomboids

Description: broad, flat, triangular muscle of low back

Origin: indirect attachment via lumbodorsal fascia into spines of lower 6 thoracic vertebrae, lumbar vertebrae and lower 3-4 ribs, iliac crest

Insertion: spirals around teres major to insert in floor of intertubercular sulcus of humerus

Action: primer mover of arm extension, arm adduction, medially rotates arm at shoulder

Latissimus dorsi

Description: (external)11 pairs lie between ribs, fibers run obliquely down and forward from rib to rib (internal)11 pairs, run deep and to right angles of external fibers

Origins: (external) inferior border of rib above (internal) superior border of rib below

Insertions: (external) superior border of rib below, (internal) inferior border of rib above

Actions: (external)aid in inspiration, (internal) aid in expiration

Intercostals internal/external

Description: medial superficial muscle pair extend from pubis to rib cage, segmented 3 sections

Origin: pubic crest and symphysis Insertion: xiphoid process and costal

cartilage Action: flex and rotate lumbar region of

vertebral column used in sit-ups and curls

Rectus Abdominis

Description: largest and most superficial of three lateral muscles, fibers run downward and medially

Origin: fleshy strips from outer surface of lower 8 ribs

Insertion: fibers insert into linea alba, pubic crest and tubercle, and iliac crest

Action: aid in flexing vertebral column, trunk rotation and lateral flexion, used in oblique curls

External Oblique

Description: most fibers run upward and medially, fans so some run down and medially

Origin: lumbar fascia, iliac crest, and inguinal ligament

Insertion: linea alba, pubic crest, last 3-4 ribs

Action: same as external oblique

Internal Obliques

Description: deepest muscle of abdominal wall, fiber run horizontally

Origin: inguinal ligament, lumbar fascia, cartilage of last 6 ribs

Insertion: linea alba, pubic crest Action: compresses abdominal contents

Transversus Abdominus

Description: thick, multi-pennate muscle forming rounded shoulder muscle mass

Origin: embraces insertion of trapezius; lateral third of clavicle, acromion and spine of scapula

Insertion: deltoid tuberosity of humerus Action: primer mover of arm abduction

Deltoid

Description: large fleshy muscle of posterior compartment of arm, 3 headed origin

Origin: long head: infraglenoid tubercle of scapula, lateral head: posterior shaft of humerus, medial head: posterior radial shaft distal to radial groove

Insertion: common tendon to olecranon process of ulna

Action: prime mover forearm extensor

Triceps brachii

Description: 2 headed fusiform muscle, bellies unite as approaching insertion

Origin: short head: corocoid process, long head: tubercle above the lip of glenoid cavity

Insertion: by common tendon to radial tuberosity

Action: flexes elbow joint and supinates forearm

Biceps brachii

Description: strong muscle that is immediately deep to biceps on distal humerus

Origin: front of distal humerus; embraces insertion of deltoid

Insertion: coronoid process of ulna Action: major forearm flexor (lifts ulna as

biceps lift radius)

Brachialis

Description: 2 headed muscle seen in superficial view between brachioradialis and flexor carpi radialis

Origin: medial epicondyle of humerus, coronoid process of ulna

Insertion: by common tendon to lateral radius, midshaft

Action: pronates forearm, weak flexor of elbow

Pronator teres

Description: superficial muscle of lateral forearm, extend from distal humerus to distal forearm

Origin: lateral supercondylar ridge at distal end of humerus

Insertion: base of styloid process of radius Action: synergist in forearm flexion

Brachioradialis

Description: Parallels brachioradialis on lateral forearm, and may blend with it

Origin: lateral supercondylar ridge of humerus

Insertion: base of 2nd metacarpal Action: extends wrist in conjunction with

extensor carpi ulnaris and abducts wrist in conjunction with flexor carpi radialis

Extensor carpi radialis longus

Description: runs diagonally across forearm, midway its fleshy belly is replaced by a flat tendon

Origin: medial epicondyle of humerus Insertion: base of 2nd and 3rd metacarpals Action: powerful flexor of wrist, abducts

hand

Flexor carpi radialis

Description: most medial of superficial posterior muscles; long slender muscle

Origin: lateral condyle of humerus and posterior border of ulna

Insertion: base of 5th metacarpal Action: Extends wrist in conjunction with the

extensor carpi radialis and adducts wrist in conjunctions with flexor carpi ulnaris

Extensor carpi ulnaris

Description: small fleshy muscle with a long insertion tendon

Origin: medial epicondyle of humerus Insertion: palmar aponeurosis; skin and

fascia of palm Action: weak wrist flexor; tenses skin and

fascia of palm during hand movement

Palmaris longus

Description: lies medial to extensor carpi radialis brevis; a detached portion of this muscle, called extensor digiti minimi, extends the little finger

Origin: lateral epicondyle of humerus Insertion: by four tendons into distal

phalanges 2-5 Action: prime mover of finger extension;

extends wrist, can abduct (flare) fingers

Extensor digitorum

Description: is a composite of two closely related muscles

Iliacus: large fan-shaped muscle (more lateral) origin: iliac fossa, crest, lateral sacrum

Psoas major: longer thicker more medial muscle (tenderlion) origin: transverse process, disks, bodies of L1-5 and T12

Insertion: lesser trochanter of femur Action: prime mover of flexing thigh and trunk

(bowing)

Iliopsoas

Description: Short, flat muscle; overlies adductor brevis on proximal thigh

Origin: pectineal line of pubis Insertion: inferior from lesser trochanter to

linea aspera of posterior femur Action: adducts, flexes, and medially rotates

thigh

Pectineus

Description: enclosed between fascia layers of anterolateral aspect of thigh, associated with medial rotators and flexors of thigh

Origin: anterior aspect of iliac crest and anterior superior iliac spine

Insertion: iliotibial tract Action: flexes and abducts thigh, rotates

thigh medially; steadies the knee and trunk on thigh by tensing iliotibial tract

Tensor fasciae latae

Description: Strap-like, superficial muscle running obliquely across anterior surface of thigh to knee, longest muscle in the body; crosses both hip and knee

Origin: anterior superior iliac spine Insertion: winds around medial aspect of

knee into medial aspect of tibia Action: flexes, abducts and laterally rotates

thigh, weak flexor of knee, “tailors muscle”

Sartorius

Description: overlies middle aspect of adductor magnus, most anterior of adductor muscles

Origin: pubis, near pubic symphysis Insertion: linea aspera Action: adducts, flexes and medially rotates

thigh

Adductor longus

Description: long, thin, superficial muscle of medial thigh

Origin: inferior ramus and body of pubis and ischial ramus

Insertion: medial surface of tibia, just inferior to its medial condyle

Action: adducts thigh, flexes and medially rotates thigh, especially during walking, flexes knee

Gracilis

Description: superficial muscle of anterior thigh, runs straight down thigh, longest head and only muscle of group to cross the hip

Origin: anterior inferior iliac spine and superior margin of acetabulum

Insertion: patela and tibial tuberosity via the patellar ligament

Action: extends knee and flexes thigh at hip

Rectus femoris

Description: largest head of the group, forms lateral aspect of thigh, common intramuscular injection site

Origin: greater trochanter, linea aspera Insertion: patella and tibial tuberosity Action: extends and stabilizes knee

Vastus lateralis

Description: forms inferomedial aspect of thigh

Origin: linea aspera, intertrochanteric line Insertion: Patella, and tibial tuburosity Action: extends knee; inferior fibers stabilize

patella

Vastus medialis

Description: The iliotibial tract, also known as the iliotibial band, is a thick strip of connective tissue connecting several muscles in the lateral thigh.

Origin: arises at its proximal end from the tendons of the tensor fasciae latae and gluteus maximus muscles.

Insertion: inserting on the lateral epicondyle of the tibia

Action: It also allows the tensor fascia latae and gluteus maximus muscles to support the extension of the knee while standing, walking, running and biking.

Iliotibial tract

Description: thick muscle largely covered by gluteus maximus, site for intramuscular injection

Origin: between anterior and posterior gleteal lines on lateral surface of ilium

Insertion: lateral aspect of greater trochanter

Action: abduct and medially rotates thigh, steadies pelvis, its action is extremely important in walking

Gluteus medius

Description: largest and most superficial muscle, forms bulk of buttock mass

Origin: dorsal ilium, sacrum, coccyx Insertion: gluteal tuberosity of femur,

iliotibial tract Action: major extensor of thigh, complex,

powerful, and most effective when thigh is flexed and force is necessary

Gluteus maximus

Description: a triangular muscle with broad insertion, is a composite muscle that is part adductor and part hamstring in action

Origin: ischial and pubic rami and ischial tuberosity

Insertion: linea aspera and adductor tubercle of femur

Action: anterior part adducts and medially rotates thigh, posterior part is synergist to hamstrings in thigh extension

Adductor magnus

Description: most lateral muscle of group, arises from two heads

Origin: ischial tuberosity, linea aspera, and distal femur

Insertion: head of fibula and lateral condyle of tibia

Action: Extends thigh and flexes knee, laterally rotates leg, especially when knee is flexed

Biceps femoris (hamstrings)

Description: lies medial to bicep femoris, it is quite fleshy, long slender tendon begins about 2/3 of way down thigh

Origin: ischial tuberosity Insertion: medial aspect of upper tibial shaft Action: Extends thigh at hip, flexes knee,

with semimembranosus, medially rotates leg

Semitendinosus

Description: Deep to the semitendinosis Origin: ischial tuberosity Insertion: medial condyle of tibia, via

oblique popliteal ligament to lateral condyle of femur

Action: extends thigh and flexes knee; medially rotates leg

Semimembranosus

Description: superficial muscle of pair, two prominent bellies that form proximal curve of calf

Origin: by two heads from medial and lateral condyles of femur

Insertion: posterior calcaneus via calcaneal tendon

Action: plantar flexes foot when knee is extended, It crosses the knee so it can flex the knee when foot is dorsiflexed

Gastrocnemius

Description: broad, flat muscle, deep to the gastrocnemius on posterior surface of calf

Origin: extensive origin from superior tibia, fibula, and interosseous membrane

Insertion: posterior calcaneus via calcaneal tendon

Action: plantar flexes foot; important locomotor and postural muscle during walking, running and dancing

Soleus

Description: superficial lateral muscle; overlies fibula

Origin: upper portion of lateral fibula Insertion: by long tendon that curves under

foot to first metatarsal and medial cuneiform

Action: plantar flexes and everts foot; may help keep foot flat on ground

Fibularis longus (peroneus)

Description: the tendon from the gastrocnemius muscle

Calcaneal tendon

Description: unipennate muscle on anterolateral surface of leg; lateral to tibialis anterior

Origin: lateral condyle of tibia, proximal ¾ of fibula, interosseous membrane

Insertion: middle and distal phalanges of toes 2-5

Action: prime mover of toe extension ( acts mainly at metatarsophalangeal joints), dorsiflexes foot

Extensor digitorum longus

Description: superficial muscle of anterior leg; laterally parallels sharp anterior margin of tibia

Origin: lateral condyle of upper 2/3 of tibial shaft; interosseous membrane

Insertion: inferior surface of medial cuneiform and first metatarsal

Action: prime mover of dorsiflexion; inverts foot, assists in supporting medial longitudinal arch

Tibialis anterior