Muscles of the Arm and Hand PSK 4U MR. S. KELLY NORTH GRENVILLE DHS Biceps Brachii Origin: scapula Insertion: radius, fascia of forearm (bicipital aponeurosis) Action: supination and elbow flexion Innervation: musculocutaneous 1
Brachialis Origin: humerus Insertion: ulna Action: elbow flexion (assists biceps brachii by instigating this movement) Lies deep to biceps brachii Innervation: musculocutaneous, radial Triceps Brachii (long, medial, and lateral heads) Origin: scapula and posterior humerus Insertion: proximal posterior ulna Action: elbow extension; shoulder extension and adduction (when elbow is extended) Innervation: axillary, radial 2
Forearm Muscles: acting on elbow, wrist, and finger joints FLEXOR-PRONATORS Originate via a common flexor tendon from medial epicondyle of humerus (common flexor origin) EXTENSOR-SUPINATORS Originates via common extensor tendon from lateral epicondyle of humerus (common extensor origin) More on the Forearm 3 layers of muscles: deep, intermediate, and superficial A layer of fascia separates deep layer of muscles from intermediate and superficial Flexor retinaculum, aka transverse carpal ligament: roof of the carpal tunnel Flexor tendons and median nerve pass through the carpal tunnel FR increases effectiveness of tendons by preventing bowstringing, changing direction of forces when necessary 3
Supinator Origin: lateral epicondyle of humerus, ulna, radial collateral ligament Insertion: proximal 1/3 of radius Action: prime mover in supination of forearm (aided by biceps brachii) Pronators PRONATOR QUADRATUS Origin: distal anterior ulna Insertion: distal anterior radius Action: prime mover in pronation of the forearm (assisted by pronator teres) Innervation: median PRONATOR TERES Origin: common flexor tendon, proximal ulna Insertion: lateral radius Action: pronation of forearm, weak elbow flexor Innervation: median 4
Pronators Flexor Digitorum Profundus Origin: ulna, interosseus membrane Insertion: phalanges, after penetrating tendons of FDS Action: flexes fingers 1-4 Innervation: anterior interosseus, ulnar 5
Flexor Policis Longus Origin: radius, interosseus membrane Insertion: distal phalanx of thumb Action: thumb flexion FPL is unique to humans: not present (or does very little) in other primates Flexor Digitorum Superficialis Origin: ulnar collateral ligament of elbow, CFO Insertion: intermediate phalanges of 4 fingers Action: flexes PIP, MP, wrist joints Innervation: median 6
Palmaris Longus Absent in about 14% of population Absence does not affect grip strength Disadvantage: absence means lack of popular source for tendon graft Test: touch pads of thumb and 5 th finger + flex wrist 2 or 3 tendons? Brachioradialis Origin: lateral humerus Insertion: styloid process of radius Action: a flexor that also works to pronate AND supinate (in supination, it pronates as it flexes, and vice versa) Innervation: median 7
Abductor Policis Longus Origin: ulna, radius, interosseus membrane Insertion: 1 st metacarpal, trapezium, abductor policis brevis tendon Action: abduction of thumb, keeps trapezium stable with APB Innervation: radial Extensor Digitorum Originates on lateral epicondyle Inserts on medial 4 digits Extends phalanges and wrist joint Insertion splits on 4 digits to medial and lateral sides. 8
Anatomical Snuff Box Extensor policis longus tendon (posterior border) Anterior (lateral) border: extensor policis brevis and abductor policis longus Skeletal components: scaphoid and trapezium Importance: blood supply of scaphoid is retrograde, therefore proximal fractures require attention to prevent necrosis Name: comes from the practice of placing powdered tobacco on this surface for sniffing. Don t ask why Primary Hand Grip Muscles (identification only) 9