3-4 Forearm and Hand

Muscles of the Forearm

• Anterior Compartment– Superficial layer– Intermediate layer– Deep layer

• Posterior Compartment– Superficial Layer– Deep Layer

Anterior Compartment: Superficial Layer

Flexor Carpi Ulnaris•Origin•Humeral head—medial epicondyle; •ulnar head—olecranon and posterior border of ulna•Insertion•Pisiform bone (via pisohamate and pisometacarpal ligaments into the hamate and base of metacarpal V)•Innervation•Ulna nerve (C7, C8, T1)•Function•Flexes and adducts the wrist joint

Palmaris Longus•Origin•Medial epicondyle of humerus•Insertion•Palmar aponeurosis of hand•Innervation•Median Nerve (C7, C8)•Function•Flexes wrist joint;• because the palmar aponeurosis anchors the skin of the hand, contraction of the muscle resists shearing forces when gripping

Flexor Capri Radialis•Origin•Medial epicondyle of humerus•Insertion•Base of metacarpals II and III•Innervation•Median Nerve (C6, C7)•Function•Flexes and abducts the wrist

Pronator teres•Origin:•Humeral head—medial epicondyle and adjacent supraepicondylar ridge• ulna head—medial side of coronoid process•Insertion•Roughening on lateral surface, midshaft, of radius•Innervation•Median Nerve (C6-C7)•Function•Pronation

Anterior Compartment: Intermediate Layer

Flexor Digitorum Superficialis•Origin•Humero-ulnar head—medial epicondyle of the humerus and adjacent margin of coronoid process •radial head—oblique line of the radius•Insertion•4 Tendons, which attach to the palmar surfaces of the middle phalanges (index, middle, ring, and little fingers)•Innervation •Median nerve (C8, T1)•Function•Flexes proximal interphalangeal joints of the fingers; also flexes metacarpophalangeal joints

Anterior Compartment: Deep Layer

Flexor Digitorum Profundus•Origin:•Anterior and medial surfaces of the ulna and anterior medial half of interosseous membrane•Insertion•Four tendons, which attach to the palmar surfaces of the distal phalanges of the index, middle, ring and little finger•Innervation•Lateral half by median nerve (ant. Interosseous nerve); medial half by ulna nerve (C8, T1)•Function•Flexes distal interphalangeal joints of the fingers; can also flex metacarpophalangeal joints of same fingers and wrist joint

Flexor pollicis longus•Origin•Anterior surface of the radius and radial half of interosseous membrane•Insertion•Palmar surface of the base of distal phalanx of thumb•Innervation•Median Nerve (anterior interosseous n.) (C7, C8)•Function•Flexes interphalangeal joint of the thumb; can also flex metacarpophalangeal joint of the Thumb

Pronator quadratus•Origin•Linear ridge on distal anterior surface of ulna•Insertion•Distal anterior surface of radius•Innervation•Median Nerve (anterior interosseous nerve) (C7, C8)•Function•Pronation

Posterior Compartment: Superficial Layer

Brachioradialis•Origin•Proximal part of lateral supraepicondylar ridge of humerus and adjacent intermuscular septum•Insertion•Lateral surface of distal end of radius•Innervation•Radial nerve (C5, C6) before division into superficial and deep branches•Function•Accessory flexor of elbow joint when forearm is midpronated

Extensor Carpi Radialis Longus•Origin•Distal part of lateral supraepicondylar ridge of humerus and adjacent intermuscular septum•Insertion•Dorsal Surface of base of metacarpal II•Innervation•Radial Nerve (C6, C7) before division into superficial and deep branches•Function•Extends and abducts the wrist

Extensor Carpi Radialis Brevis•Origin•Lateral epicondule of humerus and adjacent intermuscular septum•Insertion•Dorsal surface of base of metacarpals II and III•Innervation•Deep branch of radial nerve (C7, C8) before penetrating supinator muscle•Function•Extends and abducts the wrist

Extensor Digitorum•Origin•Lateral epicondyle of humerus and adjacent intermuscular septum and deep fascia•Insertion•4 tendons, insert via extensor hoods into the dorsal aspects of the bases of the middle and distal phalanges•Innervation•Posterior interosseous nerve (C7, C8)•Function•Extends the fingers; also can extend wrist

Extensor digiti minimi•Origin•Lateral epicondyle of humerus and adjacent intermuscular septum together with extensor digitorum•Insertion•Extensor hood of the little finger•Innervation•Posterior interosseous nerve (C7, C8)•Function•Extends the little finger•“Tea muscle”

Extensor Carpi Ulnaris•Origin•Lateral epicondyle of humerus and posterior border of ulna•Insertion•Tubercle on the base of the medial side of metacarpal V•Innervation•Posterior interosseous nerve (C7, C8)•Function•Extends and adducts the wrist

Anconeus•Origin•Lateral epicondyle of humerus•Insertion•Olecranon and proximal posterior surface of ulna•Innervation•Radial Nerve (C6, C7, C8)…via branch to medial head of triceps brachii)•Function•Abduction of the ulna in pronation; accessory extensor of the elbow joint

Posterior Compartment: Deep Layer

Supinator•Origin•Superficial part—lateral epicondule of humerus, radial collateral and unular ligaments•Deep part—supinator crest of the ulna•Insertion•Lateral surface of radius superior to the anterior oblique line•Innervation•Posterior interosseous nerve (C6, C8)•Function•Supination

Abductor pollicis longus•Origin•Posterior surfaces of ulna and radius (distal to the attachments of supinator and anconeus), and intervening interosseous membrane•Insertion•Lateral side of base of metacarpal I•Innervation•Posterior interosseous nerve (C7, C8)•Function•Abducts carpometacarpal joint of thumb; accessory extensor of the thumb

Extensor pollics brevis•Origin•Posterior surface of radius (distal to abductor pollicis longus) and the adjacent interosseous membrane•Insertion•Dorsal surface of base of proximal phalanx of the thumb•Innervation•Posterior interosseous nerve (C7, C8)•Function•Extends metacarpophalangeal joint of the thumb; can also extend the carpometacarpal joint of the thumb

Extensor pollicus longus•Origin•Posterior surface of ulna (distal to the abductor pollicis longus) and the adjacent interosseous membrane•Insertion•Dorsal Surface of base of distal phalanx or thumb•Innervation•Posterior interosseous nerve (C7, C8)•Function•Extends interphalangeal joint of the thumb; can also extend carpometacarpal and metacarpophalangeal joints of the thumb

Extensor indicis•Origin•Posterior surface of ulna (distal to extensor pollicis longus) and adjacent interosseous membrane•Insertion•Extensor hood of index finger•Innervation•Posterior interosseous nerve (C7, C8)•Funtion•Extends index finger

Vessels

Radial Artery

Radial Recurrent Artery

Radial a. in “Snuffbox”

Ulna Artery

Common Interosseous Artery

Posterior Interosseous Artery

Anterior interosseous artery

Nerves

Median Nerve

Anterior Interosseous Branch (Median n.)

Radial Nerve

Superficial Branch (Radial n.)

Deep Branch (Radial n.)

Posterior Interosseous Nerve (branch)

Posterior Antebrachial Cutaneous

Flexor Retinaculum

Carpal Tunnel

Extensor Retinaculum

Intertendinous Connections

Extensor Expansion

Hand Structures

Intrinsic Muscles of the Hand

• Thenar Muscles – 3 muscles associated with the thumb– Thenar Eminence = the prominent swelling on the

lateral side of the palm at the base of the thumb• Hypothenar Muscles — 3 muscles associated

with the little finger – Hypothenar Eminence = The swelling on medial

side of the palm at the base of the little finger

Opponens pollicis•Origin•Tubercle of trapezium and flexor retinaculum •Insertion•Lateral margin and adjacent palmar surface of metacarpal I•Innervation•Recurrent branch of median nerve (C8, T1)•Function•Medially rotates thumb

Abductor pollicis brevis•Origin•Tubercles of scaphoid and trapezium and adjacent flexor retinaculum•Insertion•Proximal phalanx and extensor hood of thumb•Innervation •Recurrent branch of median nerve (C8, T1)•Function•Flexes thumb at metacarpophalangeal joint

Flexor Pollicis Brevis•Origin•Tubercle of the trapezium and flexor retinaculum•Insertion•Proximal Phalanx of the thumb•Innervation•Recurrent branch of median nerve (C8, T1)•Function•Flexes thumb at metacarpophalangeal joint

Opponens digiti minimi•Origin•Hook of hamate and flexor retinaculum•Insertion•Medial aspect of metacarpal V•Innervation•Deep branch of ulna nerve (C8, T1)•Function•Laterally rotates metacarpal V

Abductor Digiti Minimi•Origin•Pisiform, the pisohamate ligament, and tendon of flexor carpi ulnaris•Insertion•Proximal phalanx of little finger•Innervation•Deep Branch of ulna nerve (C8, T1)•Function•Abducts little finger at metacarpophalangeal joint

Flexor digiti minimi brevis•Origin•Hook of the hamate and flexor retinaculum•Insertion•Proximal phalanx of little finger•Innervation•Deep branch of ulna nerve (C8, T1)•Function•Flexes little finger at metacarpophalangeal joint

Intrinsic muscles of hand: Adductor-Interosseous Compartment

Adductor Pollicis•Origin•Transverse head—metacarpal III; Oblique head—capitate and bases of metacarpals II and III•Insertion•Base of proximal phalanx and extensor hood of thumb•Innervation•Deep branch of ulna nerve•Function•Adducts Thumb

Palmar (Unipennate) Interosseous (4 muscles)•Origin•Sides of metacarpals•Insertion•Extensor hoods of the thumb, index, ring and little fingers and the proximal phalanx of the thumb•Innervation•Deep Branch of ulna nerve (C8, T1)•Function•Adduction of the thumb, index, ring, and little fingers at the metacarpophalangeal joints

Dorsal (Bipennate) Interosseous muscles (4)•Origin•Adjacent sides of metacarpals•Insertion•Extensor hood and base of proximal phalanges of index, middle, and ring fingers•Innervation•Deep Branch of ulna nerve (C8, T1)•Function•Abduction of index, middle, and ring fingers at the metacarphphalangeal joints

Intrinsic Hand Muscles: Central Compartment

Tendons of flexor Digitorum superficialis

Tendons of Flexor digitorum profundus

Lumbricals (4 Muscles)•Origin•Tendons of flexor digitorum profundus•Insertion•Extensor hoods of index, ring, middle, and little fingers•Innervation•Medial 2 by the deep branch of the ulna nerve; lateral 2 by digital branches of the median nerve•Function•Flex metacarpophalangeal joints while extending interphalangeal joints

Vessels: Branches of the Radial Artery

Superficial Palmar branch (radial a.)

Princeps Pollicis (Radial a. branch)P. 416 GA

Deep Palmar Arterial Arch (Radial a.)

Palmar metacarpal arteries

Branches of Ulna Artery

Deep Palmar branch (Ulna a.)

Superficial Palmar arterial arch (Ulna a.)

Common palmar digital arteries

Proper palmar digital arteries

Nerves of the Hand

Common Digital branches •Lateral 4 Branches are from the Median n.•Medial 2 Branches are from the Ulna n.

Proper Digital Nerves•Note that the Proper Digital Nerves in the ring finger are branched from both the ulna and medial nerve

Deep Branch of the Ulna n.

Recurrent Branch of the Median NerveInnervates thenar muscles

Million dollar test

Superficial Branch of Radial Nerve

Palmar Aponeurosis

Fibrous Digital sheaths