POSTERIOR (EXTENSOR) ASPECT OF FOREARM Prof. Dr. Selda nderolu Structures from superficial to deep Skin Superficial fascia- superficial vessels and nerves Skin innervation-mainly by the posterior cut. n. of forearm( radial nerve). Deep fascia ( extensor retinaculum). Muscles SKIN INNERVATION Superficial veins: Beginning of the Cephalic and basilic veins Deep fascia mm. On the post.aspect of forearm Two groups: A- Superficial B- deep Muscles-SUPERFICIAL GROUP 1- Brachioradialis m. 2-Extensor carpi radialis longus 3-Extensor carpi radialis brevis 4-Extensor carpi ulnaris 5-Extensor digitorum 6-Extensor digiti minimi 7-Anconeus (?) Muscles-DEEP GROUP 1-Supinator ( pierced by radial n.) 2-Abductor pollicis longus 3-Extensor pollicis longus 4-Extensor pollicis brevis 5-Extensor indicis (/ext.indicis proprius) BRACHIORADIALIS MUSCLE The most superficial muscle. Forms the lateral border of the cubital fossa. Or:supracondylar ridge+lat.intermuscular septum Ins:lateral side of radius (above styloid process) n.: radial nerve (itself!) F.: flexor of forearm(flexes better when forearm is pronated) EXTENSOR CARPI RADIALIS LONGUS or: supracondylar ridge ins:second metacarpal bone N: radial nerve ( itself!) F:extention of forearm and hand COMMON EXTENSOR TENDON Lateral epicondyle of humerus The extensor mm. Also orginate from: Radial collateral lig. Of elbow joint intermuscular septa. N.: all the muscles except the brachioradialis and ext. carpi rad. Longus are innervated by the deep branch of the radial nerve ( posterior interosseus nerve) Muscles originating from the common extensor tendon Extensor carpi radialis brevis m. ins: 3rd metacarpal bone Extensor digitorum m. ins:dorsal digital expansion Extensor digiti minimi m.( ext. Quinti proprius m.) ins:dorsal digital expansion Extensor carpi ulnaris m. ins: 5th metacarpal bone Anconeus m. At the back of elbow joint Helps the extension of forearm DORSAL DIGITAL EXPANSION (EXTENSOR EXPANSION) Small aponeurosis which covers the dorsum of the phalanges except the thumb. Triangular in shape. Base: covers the dorsal aspect of the metacarpophalangeal joint. then divides into 3 slips: Intermediate slip: attach to the base of second phalanx 2 lateral slips: unite and attach to the base of the distal phalanx. muscles Attaching to the dorsal digital expansion Extensor digitorum m.,(superf.m.of forearm) Extensor digiti minimi m. (superf.m.of forearm) Extensor indicis proprius m. (deep m. Of forearm) interossei mm.( hand ) Lumbrical mm.( hand ) INSERTIONS! Base of first metacarpal bone : abductor pollicis longus m. Base of second metacarpal bone : extensor carpi radialis longus m. Base of third metacarpal bone : extensor carpi radialis brevis m. Base of fifth metacarpal bone :extensor carpi ulnaris m. Muscles-DEEP GROUP Supinator ( pierced by radial n.) Abductor pollicis longus Extensor pollicis longus Extensor pollicis brevis Extensor indicis proprius Supinator m.: Or: lat.epicondyle and supinator crest of ulna ins: ant,lat,and post aspect of radius n.: deep br. Of radial n F:supination of forearm and hand Deep group of extensors O: from radius,ulna and interosseus membrane according to its position (medial or lateral) I: abd.poll.longus:1st metacarpal bone ext.poll.brevis:prox. Phalanx of thumb Ext. indicis: dors.digital expansion functions: ?? Deep branch of radial n. (post.interooseus nerve) Pierces the supinator m. Posterior interooseus artery Gives the blood supply to the extensor aspect of forearm Courses together with the post.inteross. N. ANATOMICAL SNUFF BOX When the thumb is extended. Bounded -laterally: abductor pollicis longus tendon Extensor pollicis brevis tendon -medialy: Extensor pollicis longus tendon. within: Radial a. Scaphoid bone