UE 5: Forearm 2

Pronator quadratus

Origin: distal anterior ulna Insertion: distal lateral radius Nerve: median Function: pronates forearm

Describe the anatomical snuff box.

A structure in the wrist/hand formed by the extensor pollicis longus tendon (medial border) and the extensor pollicis brevis tendon (lateral border) At the floor of the snuff box is the scaphoid bone, as well as the location where the radial artery crosses, making its way to the posterior side of the hand

Describe the major nerves of the forearm and their targets.

Axillary nerve - arises from the posterior cord of the brachial plexus Innervates the deltoid and teres minor Radial nerve - arises from the posterior cord of the brachial plexus Innervates all of the extensor muscles of the arm and antebrachium (forearm), but NOT any intrinsic hand muscles Superficial branch crosses the wrist and supplies the cutaneous surface of the dorsum of the hand Median nerve - arises from the lateral and medial cords of the brachial plexus, runs down the middle of the arm on the anterior side Innervates all flexors and pronators EXCEPT the flexor carpi ulnaris and only innervates the lateral half of the flexor digitorum profundus Ulnar nerve - arises from the medial cord of the brachial plexus and enters the antebrachium (forearm) from behind the medial epicondyle of the humerus. It later passes between the 2 heads of the flexor carpi ulnaris Innervates the flexor carpi ulnaris and the medial half of the flexor digitorum profundus

Flexor pollicis longus

Origin: anterior surface of radius, coronoid process of ulna, interosseous membrane Insertion: distal phalanx of thumb on palmar side Nerve: median Function: flexes distal phalanx of thumb, aids in flexing wrist.

Extensor indicis

Origin: distal posterior ulna, interosseous membrane Insertion: proximal phalanx of index finger Nerve: Radial Function: extends index finger, assists in extending wrist

Pronator Teres

Origin: humeral (superficial) head - medial epicondyle via common flexor tendon; ulnar (deep) head - coronoid process of ulna Insertion: lateral mid-radius Nerve: median Function: pronates forearm and flexes elbow.

Flexor digitorum superficialis

Origin: humeral head: medial epicondyle via common flexor tendon; ulnar head: coronoid process, radial head: anterior radius Insertion: middle phalanx of medial 4 digits Nerve: median Function: flexes the proximal (but NOT the distal!) interphalangeal joints, metacarpal-phalangeal joints, and flexes wrist.

Flexor carpi ulnaris

Origin: humeral head: medial epicondyle via common flexor tendon; ulnar head: olecranon Insertion: pisiform, hamate & 5th metacarpal Nerve: ulnar Function: flexes wrist, medially abducts hand; assists with elbow flexion.

Extensor carpi radialis longus

Origin: lateral distal humerus Insertion: base of 2nd metacarpal Nerve: radial Function: extend wrist, laterally abducts hand

Extensor digitorum

Origin: lateral epicondyle by common extensor tendon Insertion: Lateral and dorsal surfaces of all phalanges of medial 4 digits Nerve: radial Function: extends fingers, assists in wrist extension

Extensor digiti minimi

Origin: lateral epicondyle by common extensor tendon, Insertion: proximal phalanx of 5th digit Nerve: radial Function: extends 5th digit, assists in wrist extension

Extensor carpi ulnaris

Origin: lateral epicondyle by common extensor tendon, posterior ulna Insertion: base of 5th metacarpal Nerve: radial Function: extends wrist, medially abducts hand

Extensor carpi radialis brevis

Origin: lateral epicondyle via common extensor tendon Insertion base of 3rd metacarpal Nerve radial Function: extends wrist, laterally abducts hand

Supinator

Origin: lateral epicondyle, superior lateral ulna Insertion: lateral and anterior upper radius Nerve: deep branch of radial Function: supinates forearm

Brachioradialis

Origin: lower lateral humerus Insertion: styloid process of radius Nerve: radial Function: flexes forearm ***elbow flexor but innervated by the radial nerve, also found on the anterior side of the arm***

Flexor digitorum profundus

Origin: medial anterior ulna and interosseous membrane Insertion: distal phalanges of the medial 4 digits Nerve: median and ulnar (1/2) Function: flexes distal phalanges, aids in flexing wrist.

Flexor carpi radialis

Origin: medial epicondyle via common flexor tendon Insertion: base of 2nd & 3rd metacarpal bones Nerve: median Function: flexes wrist, radially abducts hand; assists with elbow flexion.

Palmaris longus

Origin: medial epicondyle via common flexor tendon Insertion: palmar aponeurosis Nerve: median Function: flexes wrist, assists with elbow flexion.

Extensor pollicis longus

Origin: middle posterior ulna, interosseous membrane Insertion: base of distal phalanx of thumb Nerve: Radial Function: extends distal phalanx of thumb, assists in extending wrist

Extensor pollicis brevis

Origin: posterior radius, interosseous membrane Insertion: base of proximal phalanx of thumb Nerve: radial Function: extends proximal phalanx of thumb

Abductor pollicis longus

Origin: posterior ulna and radius, interosseous membrane Insertion: lateral side of 1st metacarpal Nerve: radial Function: aBducts thumb

Describe the movements at the wrist joint, the metacarpal-phalangeal joints, the interphalangeal joints and thumb movements.

Wrist: Flexion - reducing the angle of the joint, raising the fingers anteriorly toward the forearm (antebrachium) when in anatomical position Extension - returning the wrist back to anatomical position from flexion Hyperextension - continuation of extension beyond anatomical position Radial deviation (ABduction) - side bending to the thumb side Ulnar deviation (medial deviation/ulnar abduction) - side bending toward the pinky Metacarpal-phalangeal (MCP) joints: Flexion - reducing the angle of the joint, bending toward the palmar side Extension - returning to anatomical position from flexion, straightening the fingers Hyperextension - continuation of extension, moving posteriorly toward the back of the hand ABduction - lateral movements of the fingers ADduction - lateral movement that returns the fingers to anatomical position Interphalangeal joints: Flexion - reducing the angle of the joint, bending toward the palmar side Extension - returning to anatomical position from flexion, straightening the fingers Thumb: Flexion - reducing the angle of the joint, bending toward the palmar side (curling the thumb) Extension - returning to anatomical position from flexion, straightening the thumb Hyperextension - continuation of extension, moving posteriorly toward the back of the hand ABduction - moving the thumb anteriorly to form a 90º angle ADduction - moving the thumb toward the index finger Opposition - moving the thumb in order to touch another finger (essentially a combo of flexion and ABduction) Reposition - the return of the thumb from an oppositional movement