Action of Muscles

Epicranius

Occupitalis & Frontalis connected by an aponeurosis

Occipitalis bely

Retracts scalp

Frontalis belly

Raises eyebrows

Zygomaticus major

Raises corner of mouth as in smiling

Zygomaticus minor

Raises corner of mouth as in smiling

Orbicularis oculli

Closes eyes

Orbicularis oris

Closes & protrudes lips

Levator labii superioris

Elevates upper lip as when sneering

Depressor labii inferioris

Depresses lower lip as when pouting

Risorius

Draws mouth laterally in “fake” smile

Platysma

Depresses jaw and corners of mouth

Masseter

Elevates mandible

Temporalis

Elevates mandible

Medial Pterygoid

Elevates mandible; Protracts mandible;  Lateral & medial excursion of mandible

Lateral Pterygoid

Depresses mandible; Protracts mandible; Lateral & medial excursion of mandible

Sternocleidomastoid

Flexes neck (agonist);  Rotates neck (agonist)

Scalenes

Flexes neck (synergist);   Rotates neck (synergist)

Splenius capitis

Extends head;   Rotates head

Trapezius (superior fibers)

Extends head (synergist) when scapula is stable

Diaphragm

Increases volume of thoracic cavity (Agonist)

External intercostals

Synergisy in increasing volume of thoracic cavity

Internal intercostals

Synergisy in decreasing volume of thoracic cavity

Rectus abdominus

Flexion of the torso;  compression of abdominal contents

External oblique

When only 1 contracts: contralateral rotation of torso;  When both contract: synergyst in compression of abdominal contents

Internal obliques

When only 1 contracts: ipsilateral rotation of torso;  When both contract: synergyst in compression of abdominal contents

Transverse abdominus

Compression of abdominal contents

Pectoralis minor

Protracts the scapula

Serratus anterior

Protracts the scapula

Trapezius

Rotates the scapula; Elevates the scapula; Depresses the scapula ( when occipital bone is stable)

Rhomboid major

Retracts and elevates scapula

Rhomboid minor

Retracts and elevates scapula

Pectoralis major

Flexes arm;   Adducts arm;   Rotates arm medially

Latissimus dorsi

Extends arm;   Adducts arm;   Rotates arm medially

Deltoid-anterior fibers

Flexes arm;   Rotates arm medially

Deltoid-middle fibers

Abducts arm

Deltoid-posterior fibers

Extends arm;   Rotates arm laterally

Teres major

Extends arm;   Adducts arm;   Rotates arm medially

Corachobrachialis

Flexes arm;   Adducts arm

Supraspinatus

Abducts arm

Infraspinatus

Rotates arm laterally

Teres minor

Rotates arm laterally

Subscapularis

Rotates arm medially

Brachialis

Flexion at elbow

Brachioradialis

Flexion at elbow

Triceps brachii

Extension at elbow

Pronator teres

Pronation of forearm

Flexor carpi radialis

Flexes the wrist

Palmaris longus

Anchors fascia and skin of palmar region

Flexor carpi ulnaris

Flexes the wrist

Extensor carpi radialis longus

Extends wrist

Extensor digitorum

Extends fingers (wrist)

Extensor digiti minimi

Extends little finger (wrist)

Extensor carpi ulnaris

Extends clenched fist

Supinator

Supination of forearm

Iliopsoas

Flexes thigh

Sartorius

Flexes thigh; abducts thigh;  Rotates thigh laterally (tibia is stable)

Sartorius

Flexes leg (hip bone is stable)

Tensor fascia latae

Abducts thigh;   Rotates thigh medially

Adductor longus

Adducts thigh;    Flexes thigh

Adductor magnus

Adducts thigh

Gracilis

Adducts thigh

Gracilis

Flexes leg at the knee

Rectus femoris

Extends the leg; Synergist for thigh flexion

Vastus lateralis

Extends the leg at the knee

Vastus medialis

Extends the leg at the knee

Vastus intermedius

Extends the leg at the knee

Gluteus maximus

Extends thigh

Gluteus medius

Abducts thigh;   Rotates thigh medially

Piriformis

Abducts thigh;   Rotates thigh laterally

Biceps femoris

Flexes leg at the knee

Semimembranosus

Flexes leg at the knee

Semitendinosus

Flexes leg at the knee; Extends the thigh

Tibialis anterior

Dorsiflexion;   Inversion

Gastrocnemius

Plantar flexion;   Synergist of leg flexion (at the knee)

Soleus

Plantar flexion

Tibialis posterior

Plantar flexion; Inversion

Buccinator

Compresses cheeks for blowing