Posterior Forearm Muscles

Common characteristics of posterior forearm muscles

-4 of the muscles originate at the lateral humeral epicondyle (Common extensor tendon) -2 of the muscles originate on the supracondylar ridge of the humerus -All of the muscles are innervated by the RADIAL NERVE

Extensor expansion hood

-A small tent of connective tissue -Attaches tendons of the finger extensors to the dorsum of the phalanges -Tenodesis: "Free" grip actions

Anatomical snuffbox

-Depression of the dorso-lateral side of the wrist -Medial border: Extensor pollicis longus muscle -Lateral borders: Abductor pollicis longus and extensor pollicis brevis muscles -Palpated to feel the radial artery and the scaphoid bone for fractures -Avascular: Decreased blood supply takes it longer to heal

Extensor carpi radialis longus muscle

-Depth: Deep to 3 muscles going to the thumb distally -"Long conversation": Extending your index finger to point at someone and talk to them -Origin: Lateral supracondylar ridge of the humerus -Insertion: Base of 2nd metacarpal bone -Action: Extends wrist with the rest of the extensor group *Causes WRIST ABUDCTION -Nerve innervation: Radial nerve HAS THE SAME ACTIONS AS EXTENSOR CARPI RADIALIS BREVIS MUSCLE

Extensor indicis muscle

-Depth: Deep to superficial posterior forearm muscles exiting laterally -Origin: UIna and interosseous membrane -Insertion: Extensor expansion hood of 2nd digit -Action: Extends the index finger -Nerve innervation: Radial nerve SYNERGIST OF THE EXTENSOR CARPI RADIALIS LONGUS MUSCLE IN EXTENSION OF THE INDEX FINGER

Supinator muscle

-Depth: Deep to the superficial group of muscles (It is hidden) -Origin: Lateral humeral epicondyle and ulna -Insertion: Wraps tightly around the upper 1/3 of the radius into which it inserts -Action: Rotates the radius into supination -Nerve innervation: Radial nerve BICEPS BRACHII IS A SYNERGIST OF SUPINATION

Extensor carpi radialis brevis muscle

-Depth: Partially deep to the extensor carpi radialis longus muscle -"Brief conversation": Extending your middle finger to flip someone off -Origin: Lateral humeral epicondyle via common extensor tendon -Insertion: Base of 3rd metacarpal bone -Action: Extends wrist with the rest of the extensor group *Causes WRIST ABUDCTION -Nerve innervation: Radial nerve HAS THE SAME ACTION AS EXTENSOR CARPI RADIALIS LONGUS MUSCLE

Posterior forearm muscles

-Extensors and supinators of the wrist and hand -Divided into: *7 superficial groups of muscles *5 deep groups of muscles -All of the muscles are innervated by the RADIAL NERVE

Extensor digitorum muscle

-Has no "Superficialis" or "Profundus" to its name -Origin: Lateral humeral epicondyle via common extensor tendon -Insertion: 4 tendons insert onto extensor expansion hoods in digits (Fingers) 2-5 (Excluding thumb) -Action: Agonist of wrist extension (Produces TENODESIS EFFECT) *Extends wrist with the rest of the extensor group -Nerve innervation: Radial nerve

Abductor pollicis longus muscle

-Has the most lateral tendon of the snuffbox -Depth: Deep to superficial posterior forearm muscles -Crosses the tendons of the extensor carpi radialis longus and brevis muscles -Origin: Dorsum of the radius -Insertion: Thumb -Action: Abducts and extends the thumb -Nerve innervation: Radial nerve

Extensor carpi ulnaris muscle

-Located along medial forearm -Origin: Lateral humeral epicondyle via common extensor tendon -Insertion: Base of 5th metacarpal bone -Action: Extends the wrist with the rest of the extensor muscles *Adducts the wrist -Nerve innervation: Radial nerve ANTAGONIST OF THE EXTENSOR CARPI RADIALIS LONGUS AND BREVIS MUSCLES IN ADDUCTION SYNERGIST WITH THE EXTENSOR CARPI RADIALIS AND BERVIS MUSCLES IN WRIST EXTENSION

Extensor retinaculum

-Made of a fibrous roof -Holds the extensor tendons of the forearm in place

Extensor digiti minimi muscle

-Origin: Lateral humeral epicondyle via common extensor tendon -Insertion: Extensor expansion hood for 5th digit -Action: Extends the pinky -Nerve innervation: Radial nerve THINK MINI ME FROM AUSTIN POWERS, DOCTOR EVIL'S MINI CLONE: THE EXTENSOR DIGITI MINIMI MUSCLE ONLY EXTENDS THE SMALLEST (MINI) FINGER (DOCTOR EVIL POSE)

Extensor pollicis longus muscle

-Tendon exits from the superficial muscles -Crosses tendons of the extensor carpi longus and brevis muscles -Origin: Hooks around tubercle on the dorsum of the radius -Insertion: Phalanx of the thumb -Action: Extends the thumb -Nerve innervation: Radial nerve SYNERGIST WITH THE EXTENSOR POLLICIS BREVIS MUSCLE

Extensor pollicis brevis muscle

-Tendon exits from the superficial muscles -Crosses tendons of the extensor carpi radialis longus and brevis muscles -Closely associated with the abductor pollicis longus muscle -Origin: Near the greater tubercle on the dorsum of the radius -Insertion: Phalanx of the thumb -Action: Extends the thumb -Nerve innervation: Radial nerve SYNERGIST WITH THE EXTENSOR POLLICIS LONGUS MUSCLE

Superficial posterior forearm muscles

FROM LATERAL TO MEDIAL -Brachioradialis muscle -Extensor carpi radialis longus muscle -Extensor carpi radialis brevis muscle -Extensor digitorum muscle -Extensor digiti minimi muscle -Extensor carpi ulnaris muscle -Anconeus muscle

Deep posterior forearm muscles

FROM MEDIAL TO LATERAL: -Supinator muscle -Abductor pollicis longus muscle -Extensor pollicis brevis muscle -Extensor pollicis longus muscle -Extensor indicis muscle