Muscles to Know

Masseter

Origin: Zygomatic arch and Zygomatic bone

Insertion: Lateral surface of the ramus and angle of the Mandible

Action: Elevates the Mandible

Temporalis

Origin: Temporal fossa and the Temporal fascia

Insertion: Coronoid process of the Mandible and the anterior surface of the ramus of the Mandible

Action: Elevates the Mandible; retracts the Mandible (posterior fibers)

Sternocleidomastoid

Origin: Sternal head: anterior surface of the Manubrium; clavicular head: medial 1/3rd of the Clavicle

Insertion: Mastoid process and lateral 1/2 of the superior nuchal line

Action: Draws the mastoid process down toward the same side which causes the chin to turn up toward the opposite side; acting together, the muscles of the two sides flex the neck

Buccinator

Origin: Pterygomandibular raphe, Mandible, and the Maxilla lateral to the molar teeth

Insertion: Angle of mouth and the lateral portion of the upper and lower lips

Action: Pulls the corner of mouth laterally; presses the cheek against the teeth

Pectoralis Major

Origin: Medial 1/2 of the Clavicle, Manubrium & Body of Sternum, costal cartilages of ribs 2-6, sometimes from the rectus sheath of the upper abdominal wall

Insertion: Crest of the greater tubercle of the Humerus

Action: Flexes and adducts the arm, medially rotates the arm

Pectoralis Minor

Origin: Ribs 3-5

Insertion: Coracoid process of the Scapula

Action: Draws the scapula forward, medialward, and downward

Serratus Anterior

Origin: Ribs 1-8 or 9

Insertion: Medial border of the Scapula on its costal (deep) surface

Action: it draws the scapula forward; the inferior fibers rotate the scapula superiorly

Trapezius

Origin: Medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of vertebrae C7-T12

Insertion: Lateral third of the Clavicle, medial side of the acromion and the upper crest of the Scapular spine, tubercle of the scapular spine

Action: elevates and depresses the scapula (depending on which part of the muscle contracts); rotates the scapula superiorly; retracts scapula

Latissimus Dorsi

Origin: Vertebral spines from T7 to the Sacrum, posterior third of the Iliac crest, lower 3 or 4 ribs, sometimes from the inferior angle of the scapula

Insertion: Floor of the intertubercular groove

Action: extends the arm and rotates the arm medially

Deltoid

Origin: Lateral one-third of the Clavicle, acromion, the lower lip of the crest of the spine of the Scapula

Insertion: Deltoid tuberosity of the Humerus

Action: Abducts arm; anterior fibers flex & medially rotate the arm; posterior fibers extend & laterally rotate the arm

Supraspinatus

Origin: Supraspinatous Fossa

Insertion: Greater tubercle of the Humerus (highest facet)

Action: abducts the arm (initiates abduction)

Infraspinatus

Origin: Infraspinatous fossa

Insertion: Greater tubercle of the Humerus (middle facet)

Action: laterally rotates the arm

Subscapularis

Origin: Medial two-thirds of the costal surface of the Scapula (subscapular fossa)

Insertion: Lesser tubercle of the Humerus

Action: medially rotates the arm; assists extention of the arm

Teres Minor

Origin: Upper 2/3 of the lateral border of the Scapula

Insertion: Greater tubercle of the Humerus (lowest facet)

Action: laterally rotates the arm

Teres Major

Origin: Dorsal surface of the inferior angle of the Scapula

Insertion: Crest of the lesser tubercle of the Humerus

Action: adducts the arm, medially rotates the arm, assists in arm extension

External Intercostal

Origin: Lower border of a Rib within an intercostal space

Insertion: Upper border of the Rib below, coursing, downward and medially

Action: keeps the intercostal space from blowing out or sucking in during respiration

Internal Intercostal

Origin: Upper border of a Rib

Insertion: Lower border of Rib above, coursing up and medially

Action: keeps the intercostal space from blowing out or sucking in during respiration

Rectus Abdominis

Origin: Pubis and the pubic symphysis

Insertion: Xiphoid process of the Sternum and costal cartilages 5-7

Action: flexes the trunk

Internal Oblique

Origin: Inguinal ligament, iliac crest and lumbodorsal fascia

Insertion: Ribs 10-12

Action: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso

External Oblique

Origin: Ribs 5-12

Insertion: Iliac crest and pubic tubercle

Action: Flexion and contralateral rotation of the tors

Triceps Brachii

Origin: Long head: infraglenoid tubercle of the Scapula; Lateral head: posterolateral Humerus & lateral intermuscular septum; Medial head: posteromedial surface of the inferior 1/2 of the Humerus

Insertion: Olecranon process of the Ulna

Action: extends the forearm; the long head extends and adducts arm

Biceps Brachii

Origin: Short head: tip of the coracoid process of the Scapula; Long head: supraglenoid tubercle of the Scapula

Insertion: Tuberosity of the Radius

Action: flexes the forearm, flexes arm (long head), supinates

Brachialis

Origin: Anterior surface of the lower one-half of the Humerus and the associated intermuscular septa

Insertion: Coronoid process of the Ulna

Action: flexes the forearm

Brachioradialis

Origin: Upper two-thirds of the lateral supracondylar ridge of the Humerus

Insertion: Lateral side of the base of the styloid process of the Radius

Action: flexes the elbow, assists in pronation & supination

Flexor Digitorum Superficialis

Origin: Humeroulnar head: common flexor tendon; Radial head: middle 1/3 of radius

Insertion: Shafts of the middle phalanges of digits 2-5

Action: flexes the metacarpophalangeal and proximal interphalangeal joints

Flexor Carpi Radialis

Origin: Common flexor tendon from the medial epicondyle of the Humerus

Insertion: Base of the second and third Metacarpals

Action: flexes the wrist, abducts the hand

Flexor Carpi Ulnaris

Origin: Common flexor tendon & (Ulnar head) from medial border of olecranon & upper 2/3 of the posterior border of the Ulna

Insertion: Pisiform, hook of Hamate, and base of 5th Metacarpal

Action: flexes wrist, adducts hand

Extensor Carpi Ulnaris

Origin: Common extensor tendon & the middle one-half of the posterior border of the Ulna

Insertion: Medial side of the base of the 5th Metacarpal

Action: extends the wrist; adducts the hand

Extensor Carpi Radialis Longus

Origin: Lower one-third of the lateral supracondylar ridge of the Humerus

Insertion: Dorsum of the second Metacarpal bone (base)

Action: extends the wrist; abducts the hand

Extensor Carpi Radialis Brevis

Origin: Common extensor tendon (lateral epicondyle of Humerus)

Insertion: Dorsum of the third Metacarpal bone (base)

Action: extends the wrist; abducts the hand

Extensor Digitorum

Origin: Common extensor tendon (lateral epicondyle of the Humerus)

Insertion: Extensor expansion of digits 2-5

Action: extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 2nd-5th digits; extends wrist

Rectus Femoris(Quadriceps femoris)

Origin: Straight head: anterior inferior iliac spine; Reflected head: above the superior rim of the acetabulum

Insertion: Patella and Tibial tuberosity (via the patellar ligament)

Action: extends the leg, flexes the thigh

Vastus lateralis(Quadriceps femoris)

Origin: Lateral intermuscular septum, lateral lip of the linea aspera and the gluteal tuberosity

Insertion: Patella and medial patellar retinaculum

Action: extends leg

Vastus medialis(Quadriceps femoris)

Origin: Medial intermuscular septum, medial lip of the linea aspera

Insertion: Patella and medial patellar retinaculum

Action: extends leg

Vastus Intermedius(Quadriceps femoris)

Origin: Anterior and lateral surface of the Femur

Insertion: Patella

Action: extends the leg

Sartorius

Origin: Anterior superior iliac spine

Insertion: Medial surface of the Tibia (pes anserinus)

Action: flexes, abducts and laterally rotates the thigh; flexes leg

Gluteus Maximus

Origin: Posterior gluteal line, posterior surface of Sacrum and Coccyx, sacrotuberous ligament

Insertion: Upper fibers: iliotibial tract; Lowermost fibers: gluteal tuberosity of the femur

Action: extends the thigh; laterally rotates the femur

Biceps Femoris(Hamstrings)

Origin: Long head: ischial tuberosity; Short head: lateral lip of the linea aspera

Insertion: Head of Fibula and lateral condyle of the Tibia

Action: extends the thigh, flexes the leg

Semitendinosus(Hamstrings)

Origin: Lower, medial surface of ischial tuberosity (common tendon with biceps femoris m.)

Insertion: Medial surface of Tibia (via pes anserinus)

Action: extends the thigh, flexes the leg

Semimembranosus(Hamstrings)

Origin: Upper, outer surface of the ischial tuberosity

Insertion: Medial condyle of the Tibia

Action: extends the thigh, flexes the leg

Gastrocnemius

Origin: Femur; Medial head: above the medial femoral condyle; Lateral head: above the lateral femoral condyle

Insertion: dorsum of the Calcaneus via the calcaneal (Achilles') tendon

Action: flexes leg; plantar flexes foot

Soleus

Origin: Posterior surface of head and upper shaft of the Fibula, soleal line of the Tibia

Insertion: Dorsum of the Calcaneus via the calcaneal (Achilles') tendon

Action: plantar flexes the foot

Tibialis Anterior

Origin: Lateral tibial condyle and the upper lateral surface of the Tibia

Insertion: Medial surface of the Medial Cuneiform and the 1st Metatarsal

Action: dorsiflexes and inverts the foot

Tibialis Posterior

Origin: Interosseous membrane, posteromedial surface of the Fibula, posterolateral surface of the Tibia

Insertion: Tuberosity of the Navicular and Medial Cuneiform, Metatarsals 2-4

Action: plantar flexes the foot; inverts the foo