Practical 3 Muscle Origins, Insertions, and Actions

Orbicularis Oris

Origin: muscles near the mouth

Insertion: skin of central lip

Action: closes lips, protrudes lips as for kissing

Masseter

Origin: zygomatic arch

Insertion: lateral surface of ramus of mandible

Action: elevates and protracts mandible

Sternocleidomastoid

Origin: anterior surface of sternum and upper surface of clavicle

Insertion: mastoid process of temporal bone

Action: each laterally flexes neck to the same side, rotates head to the opposite side; together they pull the head forward and down, also aid in forceful inhalation by elevating sternum and 1st ribs

Rectus Abdomonis

Origin: crest of pubis and pubic symphysis

Insertion: xiphoid process of sternum and ribs 5 - 7

Action: compresses abdomen, flexes vertebral column

Trapezius

Origin: occipital bone, ligamentum nuchae, and spinous processes of 7th cervical and all thoracic vertebrae

Insertion: clavicle, spine, and acromion process of scapula

Action: rotates and retracts scapula; superior portion elevates scapula; inferior portion depresses scapula

Pectoralis Minor

Origin: anterior surface of ribs 3 - 5

Insertion: coracoid process of scapula

Action: depresses and protracts scapula, elevates ribs during forceful inhalation

Pectoralis Major

Origin: clavicle, sternum, and costal cartilages of upper ribs

Insertion: intertubercular sulcus of humerus

Action: flexes shoulder, adducts and medially rotates arm

Latissimus Dorsi

Origin: spines of sacral lumbar and lower thoracic vertebrae, iliac crest, and lower ribs

Insertion: intertubercular sulcus of humerus

Action: extends shoulder, adducts and rotates arm medially, or depresses and retracts shoulder

Deltoid

Origin: acromion process, spine of the scapula, and the clavicle

Insertion: deltoid tuberosity

Action: lateral portion abducts arm, anterior portion flexes shoulder, posterior portion extends shoulder

Biceps Brachii

Origin: coracoid process and tubercle above glenoid cavity of scapula

Insertion: radial tuberosity

Action: flexes elbow and supinates forearm and hand

Triceps Brachii

Origin: tubercle below glenoid cavity and lateral/posterior surfaces of humerus

Insertion: lateral surface of radius above styloid process

Action: extends elbow

Biceps Femoris

Origin: ischial tuberosity and linea aspera of femur

Insertion: head of fibula

Action: flexes knee, laterally rotates leg, and extends hip

Semitendinosus

Origin: ischial tuberosity

Insertion: proximal/medial surface of tibia

Action: flexes knee, medially rotates leg, and extends hip

Semimembranosus

Origin: ischial tuberosity

Insertion: medial condyle of tibia

Action: flexes knee, medially rotates leg, and extends hip

Rectus Femoris

Origin: anterior superior iliac spine and margin of acetabulum

Insertion: patella by tendon (continues as patellar ligament to tibial tuberosity)

Action: extends knee, flexes hip

Vastus Lateralis

Origin: greater trochanter and posterior surface of femur

Insertion: patella by tendon (continues as patellar ligament to tibial tuberosity)

Action: extends knee

Vastus Intermedius

Origin: anterior and lateral surfaces of femur

Insertion: patella by tendon (continues as patellar ligament to tibial tuberosity)

Action: extends knee

Vastus Medialis

Origin: medial surface of femur

Insertion: patella by tendon (continues as patellar ligament to tibial tuberosity)

Action: extends knee