Muscles: Action and Attachments Study Guide

Vocabulary practice cards outlining the muscles and muscle groups for which students are required to know actions, attachments, or both.

Major joints

The joints whose prime movers require knowledge of both actions and attachments: vertebrae, shoulder, elbow, wrist, hip, knee, and ankle.

Muscles of facial expression

A subset of muscles for which students need to know the action, but do not need to know attachments.

Extrinsic ocular muscles

A subset of eye muscles for which students need to know the action, but do not need to know attachments.

Lab guide for the muscular system

The provided guide that contains detailed information on muscle attachments.

Frontalis

Action: Raises eyebrows and wrinkles forehead skin horizontally.

Orbicularis oculi

Action: Closes eyelids (blinking, squinting, and winking).

Orbicularis oris

Action: Closes, compresses, and protrudes the lips (the kissing muscle).

Masseter

Action: Elevates and protracts the mandible to close the jaw during mastication.

Zygomaticus major

Action: Elevates and draws the angle of the mouth laterally and upward (smiling).

Depressor anguli oris

Action: Depresses the angle and corner of the mouth (frowning).

Platysma

Action: Tenses skin of the neck, depresses lower lip, and assists in depressing the mandible.

Superior oblique

Action: Intorsion, depression, and abduction of the eyeball (directs gaze downward and laterally).

Inferior oblique

Action: Extorsion, elevation, and abduction of the eyeball (directs gaze upward and laterally).

Superior rectus

Action: Elevates the eyeball; also assists in adduction and intorsion.

Medial rectus

Action: Adducts the eyeball (directs gaze medially toward the nose).

Lateral rectus

Action: Abducts the eyeball (directs gaze laterally).

Inferior rectus

Action: Depresses the eyeball; also assists in adduction and extorsion.

Erector spinae

Action: Extends and laterally flexes the vertebral column; maintains upright posture. Attachments: Origin: Iliac crest, sacrum, and lumbar/thoracic spinous processes; Insertion: Ribs, transverse and spinous processes of cervical and thoracic vertebrae, and mastoid process.

Rectus abdominis

Action: Flexes the vertebral column and compresses abdominal viscera. Attachments: Origin: Pubic crest and pubic symphysis; Insertion: Xiphoid process of sternum and costal cartilages of ribs 5-7.

External oblique

Action: Bilaterally flexes vertebral column and compresses abdomen; unilaterally laterally flexes and rotates trunk to opposite side. Attachments: Origin: External surfaces of ribs 5-12; Insertion: Linea alba, pubic tubercle, and anterior iliac crest.

Sternocleidomastoid

Action: Bilaterally flexes the cervical spine and neck; unilaterally rotates head to the opposite side and laterally flexes head to the same side. Attachments: Origin: Manubrium of sternum and medial clavicle; Insertion: Mastoid process of temporal bone and superior nuchal line of occipital bone.

Pectoralis major

Action: Adducts, medially rotates, and flexes the arm at the shoulder joint. Attachments: Origin: Clavicular head (medial clavicle) and sternocostal head (sternum and costal cartilages 1-6); Insertion: Crest of greater tubercle (lateral lip of bicipital groove) of humerus.

Latissimus dorsi

Action: Extends, adducts, and medially rotates the arm at the shoulder joint. Attachments: Origin: Spinous processes of T7-L5, thoracolumbar fascia, iliac crest, and lower ribs; Insertion: Floor of intertubercular sulcus (bicipital groove) of humerus.

Deltoid

Action: Abducts arm at shoulder joint (middle fibers); anterior fibers flex and medially rotate; posterior fibers extend and laterally rotate. Attachments: Origin: Lateral third of clavicle, acromion, and spine of scapula; Insertion: Deltoid tuberosity of humerus.

Triceps brachii

Action: Extends forearm at elbow joint; long head extends and adducts arm at shoulder joint. Attachments: Origin: Infraglenoid tubercle of scapula (long head), posterior humeral shaft (lateral and medial heads); Insertion: Olecranon process of ulna.

Biceps brachii

Action: Flexes and supinates forearm at elbow and radioulnar joints; weakly flexes arm at shoulder joint. Attachments: Origin: Supraglenoid tubercle (long head) and coracoid process (short head) of scapula; Insertion: Radial tuberosity and bicipital aponeurosis.

Brachialis

Action: Major flexor of the forearm at the elbow joint in all forearm positions. Attachments: Origin: Distal anterior shaft of humerus; Insertion: Coronoid process and tuberosity of ulna.

Flexor carpi group

Action: Flexes the hand at the wrist joint and produces radial or ulnar deviation. Attachments: Origin: Medial epicondyle of humerus via common flexor tendon; Insertion: Bases of metacarpals II-V, pisiform, and hamate.

Extensor carpi group

Action: Extends the hand at the wrist joint and produces radial or ulnar deviation. Attachments: Origin: Lateral epicondyle of humerus via common extensor tendon; Insertion: Bases of metacarpals II, III, and V.

Pronator teres

Action: Pronates the forearm at radioulnar joints and weakly flexes the elbow joint. Attachments: Origin: Medial epicondyle of humerus and coronoid process of ulna; Insertion: Mid-lateral surface of the radial shaft.

Iliopsoas

Action: Major flexor of the thigh at the hip joint; flexes trunk toward thigh during sit-ups. Attachments: Origin: Iliac fossa (iliacus) and bodies/transverse processes of T12-L5 (psoas major); Insertion: Lesser trochanter of femur.

Quadriceps femoris

Action: Extends the leg at the knee joint; rectus femoris also flexes the thigh at the hip joint. Attachments: Origin: Anterior inferior iliac spine (rectus femoris) and femoral shaft/linea aspera (vasti muscles); Insertion: Tibial tuberosity via the patellar ligament.

Adductor group of thigh

Action: Adducts, medially rotates, and flexes the thigh at the hip joint. Attachments: Origin: Pubic body, inferior pubic ramus, and ischial ramus/tuberosity; Insertion: Linea aspera and adductor tubercle of femur.

Gluteus maximus

Action: Major extensor and lateral rotator of the thigh at the hip joint. Attachments: Origin: Posterior ilium, iliac crest, sacrum, and coccyx; Insertion: Gluteal tuberosity of femur and iliotibial (IT) tract.

Gluteus medius

Action: Abducts and medially rotates the thigh at the hip joint; stabilizes pelvis during ambulation. Attachments: Origin: Outer lateral surface of ilium between anterior and posterior gluteal lines; Insertion: Greater trochanter of femur.

Hamstrings

Action: Flex the leg at the knee joint and extend the thigh at the hip joint. Attachments: Origin: Ischial tuberosity (and linea aspera for short head of biceps femoris); Insertion: Head of fibula (biceps femoris) and proximal medial tibia (semitendinosus and semimembranosus).

Gastrocnemius

Action: Plantar flexes the foot at the ankle joint and flexes the leg at the knee joint. Attachments: Origin: Medial and lateral condyles of femur; Insertion: Posterior calcaneus via the calcaneal (Achilles) tendon.

Tibialis anterior

Action: Dorsiflexes and inverts the foot at the ankle and subtalar joints. Attachments: Origin: Lateral condyle and proximal lateral shaft of tibia, plus interosseous membrane; Insertion: Medial cuneiform and base of first metatarsal.

Vertebrae

Prime movers (actions and attachments required): Erector spinae, rectus abdominis, external oblique, and sternocleidomastoid.

Shoulder

Prime movers (actions and attachments required): Pectoralis major, latissimus dorsi, and deltoid.

Elbow

Prime movers (actions and attachments required): Triceps brachii, biceps brachii, brachialis, and pronator teres.

Wrist

Prime movers (actions and attachments required): Flexor carpi group and extensor carpi group.

Hip

Prime movers (actions and attachments required): Iliopsoas, quadriceps femoris (rectus femoris), adductor group of thigh, gluteus maximus, gluteus medius, and hamstrings.

Knee

Prime movers (actions and attachments required): Quadriceps femoris, hamstrings, and gastrocnemius.

Ankle

Prime movers (actions and attachments required): Gastrocnemius and tibialis anterior.