Muscles of the Body Action

Anatomy & Physiology

Muscles of the Body – Action

Muscles of the Head & Neck:

Frontalis: Elevates the eyebrow; wrinkles forehead horizontally.

Orbicularis Oculi: Closes the eyelids; causes squinting & blinking.

Orbicularis Oris: Draws lips together; pucker.

Zygomaticus: Raises corner of mouth laterally as in smiling or laughing.

Buccinator: Compresses the cheek to hold food during chewing.

Platysma: Depresses corner of mouth; pouting.

Masseter: Raises mandible & draws it forward.

Occipitalis: Draws scalp backward.

Temporalis: Raises mandible. Covers temporal bone in head.

Mentalis: wrinkles chin.

Sternocleidomastoid: Flexes head & bends it laterally.

Muscles of the Thorax:

Pectoralis Major: Adducts, flexes & rotates Humerus medially. Arm forward across chest.

Pectoralis Minor: Draws scapula forward (protracts) & downward.

Serratus Anterior: draws scapula forward, downward, & inward toward chest wall.

External Intercostals: Elevate ribs & enlarge thorax.

Internal Intercostals: Draw adjacent ribs together.

Trapezius: Hyperextension of head; adducts scapula. Upper trap raises scapula.

Diaphragm: Expands thorax; compresses contents of abdominal cavity. (breathing)

Latissimus dorsi
Action: Adducts, extends, internally rotates, and horizontally abducts the arm; swimming
Rhomboideus major
Action: Adduction and downward rotation of the scapula
Rhomboideus minor
Action: Adduction and downward rotation of the scapula
Teres minor
Action: External rotation and horizontal abductionof the arm
Levator scapulae
Action: Extension of neck, downward rotation and elevation of the scapulae
Erector spinae
Action: Extension, lateral flexion and rotation of the head and neck
Shoulder, Chest and Arm Muscles

Muscles of Upper Extremity:

Anterior Deltoid: Abducts, flexes, internally rotates & horizontally adducts the arm.

Medial Deltoid: Abducts the arm

Posterior Deltoid: Abducts, extends, externally rotates & horizontally abducts the arm.

Coracobrachialis
Action: Flexes and horizontally adducts the arm

ROTATOR CUFF: SITS

Subscapularis
Action: Internally rotates the arm
Infraspinatus
Action: Externally rotates the arm
Teres Minor
Action: Externally rotates the arm
Supraspinatus
Action: Abduction of the arm

Muscles of the Arm

Biceps brachii
Action: Flexion of the elbow and shoulder, supination of the forearm
Brachialis
Action: Flexion of the elbow
Pronator teres
Action: Pronates the forearm
Triceps brachii
Action: Extends the elbow, adducts and extends the shoulder (long head)
Anconeus
Action: Extends the elbow
Supinator
Action: Supinates the forearm
Pronator quadratus
Action: Pronates the forearm
Flexor carpi radialis
Action: Flexes and abducts the wrist
Flexor carpi ulnaris
Action: Flexes and adducts the wrist
Palmaris longus
Action: Flexion of the wrist
Extensor carpi radialis longus
Action: Extends and adducts the wrist
Extensor digitorum
Action: Extends the wrist

LEGS

QUADRICEPS

Rectus femoris
Action: hip flexion and knee extension
Vastus lateralis
Action: knee extension
Vastus medialis
Action: knee extension
Vastus Intermedius
Action: knee extension

OTHER

Sartorius
Action: flexion, external rotation, and abduction at the hip, flexion and internal rotation at the knee
Gracilis
Action: abduction, flexion, and internal rotation at the hip, internal rotation of the knee
Pectineus
Action: adduction, flexion, and horizontal adduction at the hip
Adductor longus
Action: adduction, flexion, and horizontal adduction at the hip
Adductor magnus
Action: adduction, flexion, and horizontal adduction at the hip

HAMSTRINGS

Semimembranosus
Action: extension a the hip, and flexion and internal rotation at the knee
Semitendinosus
Action: extension and internal rotation at the hip, flexion and internal rotation at the knee
Biceps Femoris
Action: extension at the hip, external rotation and flexion at the knee
Gluteus maximus
Action: extension, external rotation, horizontal abduction, and adduction at the hip
Gluteus medius
Action: abduction, horizontal abduction, internal rotation (anterior fibers), and external rotation (posterior fibers) at the hip
Gluteus minimus
Action: abduction, horizontal abduction, and internal rotation at the hip

LOWER LEG

Tibialis anterior
Action: dorsiflexion and inversion of the foot
Extensor digitorum longus
Action: dorsiflexion and eversion of the foot
Extensor hallucis longus
Action: inversion of the foot
Peroneus longus
Action: plantarflexion and eversion of the foot
Soleus
Action: plantarflexion
Gastrocnemius
Action: plantarflexion of the foot, flexion of the knee

TRUNK/ABDOMEN

Rectus abdominis
Action: flexion and lateral flexion of the trunk
External oblique
Action: flexion of the trunk, lateral flexion (same side), and rotation (opposite side)
Internal oblique
Action: flexion of the trunk, lateral flexion (same side), rotation (same side)
Serratus anterior
Action: protraction and upward rotation of the shoulder girdle
Tranversalis abdominis
Action: compresses the abdominal/pelvic cavity.