Anatomy & Physiology 210 - Muscles

Muscle and its action

Sternocleidomastoid

Individually: laterally flexes head and neck to the same side, rotates head to the opposite side

Together: pull the head forward and down; also aid in forceful inhalation by elevating sternum and first ribs

Splenius capitis

Individually: rotates head to the same side

Together: bring head into an upright position

Semisplinalis capitis

Individually: rotates head to the opposite side

Together: extend head and neck

Trapezius

Rotates and retracts scapula

Superior portion elevates scapula

Inferior portion depresses scapula

Rhomboid major

Elevates and retracts scapula

Levator scapulae

Elevates scapula

Pectoralis major

Flexes arm at shoudler, adducts and medially rotates arm

Latissimus dorsi

Extends arm at shoulder, adducts and medially rotates arm

Deltoid

Lateral portion abducts arm

Anterior portion flexes arm at shoulder

Posterior portion extends arm at shoulder

Biceps brachii

Flexes forearm at elbow, supinates forearm and hand

Brachialis

Flexes forearm at elbow

Brachioradialis

Flexes forearm at elbow

Triceps brachii

Extends forearm at elbow

External Oblique

Compresses abdomen, flexes and rotates vertebral column

Internal oblique

Compresses abdomen, flexes and rotates vertebral column

Rectus abdominis

Compresses abdomen, flexes vertebral column

Psoas major

Flexes thigh at hip

Iliacus

Flexes thigh at hip

Gluteus maximus

Extends thigh at hip, laterally rotates thigh

Tensor fasciae latae

Abducts thigh, medially rotates thigh

Biceps femoris

Flexes leg at knee, extends thigh at hip

Semitendinosus

Flexes leg at knee, extends thigh at hip

Semimembranosus

Flexes leg at knee, extends thigh at hip

Rectus femoris

Extends leg at knee, flexes thigh at hip

Vastus lateralis

Extends leg at knee

Vastus medialis

Extends leg at knee

Vastus intermedius

Extends leg at knee (beneath rectus femoris)

Tibialis anterior

Dorsiflexion and inversion of foot

Gastrocnemius

Plantar flexion of foot, extension of four lateral toes

Soleus

Plantar flexion of foot

Epicranius

Elevates eyebrow

Orbicularis oculi

Closes eye

Orbicularis oris

Closes and protrudes lips

Buccinator

Compresses cheeks

Zygomaticus

Elevates corner of mouth

Platysma

Depresses lower lip and angle of mouth

Masseter

Elevates and protracts mandible

Temporalis

Elevates and retracts mandible