Muscle Anatomy and Innervation Quiz: Upper Extremity

Upper Extremity Muscles

• Trapezius: Originates at the medial part of the superior nuchal line, ligamentum nuchae, and thoracic spinous processes. Inserts onto the lateral part of the clavicle, acromion, and spine of the scapula. Innervated by the spinal accessory nerve (CN XI). Acts as a whole to rotate the scapula upward, or individually, for upward rotation (upper trap), retraction (middle trap), or depression and upward rotation (lower trap).
• Latissimus Dorsi: Originates from spinous processes of T7-T12, lumbar aponeurosis, crest of ilium, and lower three or four ribs. Inserts onto the floor of the bicipital groove of the humerus. Innervated by the thoracodorsal nerve. Actions include shoulder extension, internal rotation, adduction, and can contribute to scapular depression and retraction.
• Levator Scapulae: Originates from transverse processes of C1-C4. Inserts onto the superior angle and medial border of the scapula. Innervated by the dorsal scapular nerve. Elevates the scapula and performs downward rotation.
• Rhomboid Minor: Originates from spinous processes of C7 and T1. Inserts onto the vertebral border of the scapula at the base of the spine. Innervated by the dorsal scapular nerve. Elevates and downwardly rotates the scapula.
• Rhomboid Major: Originates from spinous processes of T2-T5. Inserts onto the vertebral border of the scapula below the rhomboid minor. Innervated by the dorsal scapular nerve. Elevates and downwardly rotates the scapula.
• Serratus Posterior Superior: Originates from spinous processes of C7-T2. Inserts onto the upper ribs. Innervated by the intercostal nerves. Acts to elevate the ribs in inspiration.
• Serratus Posterior Inferior: Originates from spinous processes of T11-L2. Inserts onto the lower ribs. Innervated by the intercostal nerves. Depresses the ribs in exhalation.
• Deltoid: Originates from the lateral third of the clavicle, acromion, and spine of the scapula. Inserts onto the deltoid tuberosity of the humerus. Innervated by the axillary nerve. Acts as a whole to stabilizes the glenohumeral joint or individually, the anterior fibers for flexion and horizontal adduction, middle fibers for abduction, and posterior fibers for extension and horizontal abduction.
• Subscapularis: Originates from the subscapular fossa. Inserts onto the lesser tubercle of the humerus. Innervated by the upper and lower subscapular nerves. Stabilizes the glenohumeral joint and rotates the humerus internally.
• Supraspinatus: Originates from the supraspinous fossa. Inserts onto the superior facet of the greater tubercle of the humerus. Innervated by the suprascapular nerve. Primarily abducts the humerus.
• Infraspinatus: Originates from the infraspinous fossa. Inserts onto the middle facet of the greater tubercle of the humerus. Innervated by the suprascapular nerve. Primarily rotates the humerus externally.
• Teres Minor: Originates from the lateral border of the scapula above teres major. Inserts onto the lower facet of the greater tubercle of the humerus. Innervated by the axillary nerve. Primarily externally rotates the humerus.
• Teres Major: Originates from the lower lateral border of the scapula, as far as the inferior angle. Inserts onto the medial lip of the bicipital groove, inferior to the insertion of the latissimus dorsi. Innervated by the lower subscapular nerve. Primarily adducts, internally rotates, and extends the humerus.

Additional Upper Extremity Muscles and Actions (Page 2-8)

• Coracobrachialis: Short head, coracoid process. Long head, supraglenoid tubercle (blends with labrum). Functions in flexion, adduction, and internal rotation of the shoulder.
• Biceps Brachii: Short head, coracoid process. Long head, supraglenoid tubercle. Flexes and supinates the forearm, flexes the shoulder.
• Brachialis: Lower, anterior humerus. Flexes the elbow.
• Triceps Brachii: Long head, infraglenoid tubercle. Extends the elbow.
• Anconeus: Lateral epicondyle, posterior humerus. Extends the elbow.
• Pectoralis Major: Clavicular, sternal. Flexes, adducts, internally rotates shoulder.
• Pectoralis Minor: Ribs 2-5. Draws scapula forward and downward.
• Subclavius: First rib. Stabilizes and depresses the clavicle.
• Pronator Teres: Medial epicondyle (common flexor origin) and coronoid process of ulna. Pronates and flexes the forearm.
• Flexor Carpi Radialis: Medial epicondyle (common flexor origin). Flexes and radially deviates wrist.
• Palmaris Longus: Medial epicondyle (common flexor origin). Flexes and radially deviates wrist, tenses the palmar fascia.
• Flexor Carpi Ulnaris: Medial epicondyle (common flexor origin), proximal ulna. Flexes and ulnarly deviates wrist.
• Flexor Digitorum Superficialis: Upper 3/4 ulna, interosseous membrane. Flexes proximal phalanges and wrist.
• Flexor Digitorum Profundus: Upper 3/4 ulna, interosseous membrane, extends wrist.. Flexes distal interphalanges.
• Pronator Quadratus: Distal ulna. Pronates forearm.
• Palmaris Brevis: Hypothenar fascia. Flexes the metacarpophalangeal (MCP) joint of the thumb.
• Lumbricals: Flexes the MCP joint and extends the IP joints of fingers.
• Adductor Pollicis: Flexor retinaculum, trapezium/trapezoid. Abducts and adducts thumb.
• Abductor Pollicis Brevis: flexor retinaculum, trapezium. Abducts thumb.
• Opponens Pollicis: flexor retinaculum, trapezium. Opposes thumb.
• Abductor Digiti Minimi: pisiform bone. Abducts the little finger.
• Opponens Digiti Minimi: pisiform bone. Opposes the little finger.
• Brachioradialis: Upper lateral supracondylar ridge of humerus, lateral radius above styloid process. Flexes the elbow and supinates or pronates forearm.
• Extensor Carpi Radialis Longus: Lateral epicondyle of humerus. Extends and radially deviates the wrist.
• Extensor Carpi Radialis Brevis: Lateral epicondyle, radius. Extends and radially deviates the wrist.
• Extensor Digitorum: Lateral epicondyle, radius. Extends the digits.
• Extensor Digiti Minimi: Lateral epicondyle, radius. Extends the little finger.
• Extensor Carpi Ulnaris: Lateral epicondyle, radius. Extends and ulnarly deviates the wrist.
• Supinator: Lateral epicondyle, ulna and radius. Supinates the forearm.
• Abductor Pollicis Longus: Posterior ulna, proximal radius. Abducts the thumb.
• Extensor Pollicis Longus: Posterior ulna, proximal radius. Extends the thumb.
• Extensor Pollicis Brevis: Posterior ulna. Abducts and extends the thumb.
• Extensor Indicis: Posterior distal ulna. Extends the index finger.