Origins, Insertions, and Actions of Muscular System

Frontalis

O: Epicranial Aponeurosis

I: Skin of the Eyebrows

A: Elevates eyebrows, wrinkles skin on forehead horizontally

Occipitalis

O: Occipital Bone

I: Epicranial Aponeurosis

A: Pulls scalp poteriorily

Orbicularis Oculi

O: Orbital portions of the frontal bone and maxilla

I: Skin of the orbital area and eyelids

A: Pulls skin around eyes (blinking and squinting), closes eye

Orbicularis Oris

O: Maxilla and Mandible

I: Skin and connective tissue of the lips

A: Closes and protrudes lips (pursing the lips)

Temporalis

O: Lateral surface of the skull

I: Coronoid process of the mandible

A: Elevates and retracts the mandble

Sternocleidomastoid

O: Manubrium of sternum, medial portion of clavicle

I: Mastoid process of temporal bone

A: Flex head, rotate head toward opposite side

Sternohyoid

O: Posterior Manubrium of sternum

I: Inferior portion of hyoid bone

A: Depresses bone (hyoid bone) and larynx

External Intercostals

O: Lower edge of rib superior to its insertion

I: Upper edge of rib inferior to its origin

A: Elevate the rib cage, spreading the ribs, assisting inspiration

Internal Intercostals

O: Upper edge of rib inferior to its insertion

I: Lower edge of rib superior to origin, deep to insertion of external intercostals

A: Depresses the rib cage, pulling ribs closer together, assisting forced expiration

Diaphragm

O: Xiphoid process of sternum, lower ribs and costal cartilages, lumbar vertebrae

I: Central tendon of diaphragm

A: Flattens, lowering the "floor" of the thoracic cavity and increasing its volume, causing aspiration (inhalation)

Pectoralis Major

O: Medial clavicle, sternum, costal cartilages 1-7

I: Greater tubercle & lateral lip of intertubercular sulcus of humerus

A: Flexes and adducts the arm; rotates arm medially

Deltoid

O: Acromion and spine of scapula; lateral clavicle

I: Deltoid tuberosity of humerus

A: Abducts the arm; secondarily flexes and extends the arm

Supraspinatus

O: Supraspinous fossa of scapula

I: Greater tubercle of humerus

A: Assists abduction; holds the humerus and stabilizes shoulder joint

Teres Minor

O: Posterior, lateral border of scapula

I: Greater tubercle of humerus

A: Laterally rotates the humerus; stabilizes shoulder joint

Infraspinatus

O: Infraspinous fossa of scapula

I: Greater tubercle of humerus

A: Laterally rotates the humerus; stabilizes shoulder joint

Subscapularis

O: Subscapular fossa of the scapula

I: Lesser tubercle of humerus

A: Adducts and rotates the humerus medially; stabilizes shoulder joint

Biceps Brachii

I: Supraglenoid tubercle and coracoid process

O: Radial tuberosity

A: Supinates the forearm; flexes the forearm

Triceps Brachii

O: Infraglenoid tubercle; posterior, proximal diaphysis, posterior diaphysis

I: Olecranon process

A: Extends the forearm

Rectus Femoris

O: Anterior inferior iliac spine, superior margin of acetabulum

I: Patella and tibial tuberosity

A: Extends the leg; flexes the thigh

Vastus Lateralis

O: Greater trochanter, intertrochanteric line, proximal half of the linea aspera

I: Patella and tibial tuberosity

A: Extends the leg; stabilizes patella

Vastus Medialis

O: Linea Aspera, intertrochanteric line

I: Patella and tibial tuberosity

A: Extends the leg; stabilizes patella

Vastus Intermedius

O: Anterior and lateral portions of proximal 2/3 of diaphysis of femur

I: Patella and tibial tuberosity

A: Extends the leg

Biceps Femoris

O: Ischial tuberosity and distal half of posterior

I: Head of fibula; lateral condyle of tibia

A: Extends the leg

Semitendinosus

O: Ischial tuberosity

I: Proximal medial surface of tibia

A: Extends the thigh; flexes the leg

Semimebranosus

O: Ischial tuberosity

I: Posterior surface of medial condyle of tibia

A: Extends the thigh; flexes the leg

Gastrocnemius

O: Medial and lateral condyles of the femur

I: Posterior calcaneous

A: Plantarflexes the foot; flexes leg