Skeletal Muscle Actions and Functions

These flashcards cover key skeletal muscles, their actions, and functions as learned in Biology 141.

Buccinator

Compresses cheek.

Orbicularis oris

Closes and purses lips.

Orbicularis oculi

Closes eye.

Epicranius (occipitofrontalis)

Includes frontal belly (raises eyebrows, wrinkles forehead) and occipital belly (draws scalp posteriorly).

Platysma

Tenses skin of neck; depresses mandible; pulls lower lip back and down.

Masseter

Elevates and protracts mandible.

Temporalis

Elevates and retracts mandible.

Sternocleidomastoid

Single – lateral flexion; rotation to opposite side; Dual – neck flexion.

External intercostals

Elevates ribs (during inspiration).

Internal intercostals

Depresses ribs (during forced expiration).

Diaphragm

Flattens to increase thoracic volume for inspiration.

Rectus abdominis

Pulls ribs downward, flexes vertebral column, compresses abdomen.

External oblique

Laterally flexes and rotates vertebral column; compresses abdomen.

Levator scapulae

Elevates and adducts scapula; neck flexion to same side.

Pectoralis minor

Depresses and protracts scapula.

Rhomboid minor

Retracts (adducts) and stabilizes scapula.

Serratus anterior

Protracts (abducts) and holds scapula against body wall.

Pectoralis major

Flexion, adduction, and medial rotation at shoulder.

Deltoid

Arm abduction; anterior fibers flex and medially rotate; posterior fibers extend and laterally rotate.

Subscapularis

Medial rotation of arm.

Biceps brachii

Flexion and supination of forearm; arm flexion (long head only).

Triceps brachii

Extension of forearm; arm extension and adduction (long head only).

Flexor carpi radialis

Flexion and abduction of hand.

Gluteus maximus

Extension, abduction, and lateral rotation of thigh.

Iliacus

Flexion of thigh and trunk flexion.

Sartorius

Flexion, abduction, and lateral rotation of thigh; knee flexion.

Quadriceps femoris

Extension of leg; hip flexion (Rectus femoris crosses hip joint).

Tibialis anterior

Dorsiflexion; inversion of foot.

Gastrocnemius

Plantar flexion; flexion at knee.