e. Brachialis -deep to biceps brachii and is most powerful flexor of forearm at the elbow joint -‘workhorse’ of the elbow flexors -origin= distal, anterior surface of humerus -insertion= ulnar tuberosity and coronoid process of ulna -action= flexes forearm at elbow joint -innervation= musculocutaneous and radial nerves f. Brachioradialis -lower down than biceps and brachialis- mostly along radius -action= flexes forearm at the elbow joint, especially when a quick movement is required or when a weight is lifted slowly during flexion of the forearm; supinates and pronates forearm at radioulnar joints to neutral position Posterior (Extensor) Compartment: Forearm Extensors a. Triceps brachii -large muscle on posterior surface of arm -more powerful of extensors at elbow joint -three heads of origin: long head from scapula, lateral and medial heads from humerus -long head crosses the shoulder joint -origin= long head originates from infraglenoid tubercle (projection inferior to glenoid cavity of scapula); lateral head originates from lateral and posterior surface of humerus; medial head originates from entire posterior surface of humerus inferior to a groove for the radial nerve -insertion= olecranon of ulna -action= extends forearm at elbow joint and extends arm at shoulder joint -innervation= radial nerve g. Anconeus (not part of Posterior compartment) -small muscle located on lateral part of posterior aspect of elbow -assists triceps brachii in extending the forearm at the elbow joint Forearm Pronators -these muscles pronate forearm at radioulnar joints -innervated by median nerve a. Pronator teres h. Pronator quadratus -distal portion of shaft of ulna -shaped like a square Forearm Supinator a. Supinator -supinates forearm at radioulnar joints -innervated by deep radial nerve Muscles of the Forearm that Move the Wrist, Hand, Thumb, and Digits -extrinsic muscles of the hand act on the digits and originate outside the hand and insert within it -tendons of the forearm muscles that attach to the wrist or into the hand, along with BVs and nerves are held close to bones by strong fasciae -tendons surrounded by tendon sheaths
-wrist has deep fascia thickened into fibrous retinacula - flexor retinaculum is located over palmar surface of carpal bones; the long flexor tendons of the digits and wrist and the median nerve pass deep to the flexor retinaculum - extensor retinaculum is located over dorsal surface of carpal bones; extensor tendons of wrist and digits pass deep to it Anterior (Flexor) Compartment: -originate on the humerus -typically insert on the carpals, metacarpals, and phalanges -function primarily as flexors -bellies of these muscles are the bulk of the forearm 1. Superficial Anterior (Flexor) Compartment of the Forearm -flex and abduct hand at wrist joint; flex middle phalanx -listed muscles are arranged lateral to medial a. Flexor carpi radialis i. Palmaris longus -missing in 10% of individuals (usually in left forearm) -commonly used for tendon repair j. Flexor carpi ulnaris -ulnar nerve and artery are just lateral to the tendon of this muscle at the wrist k. Flexor digitorum superficialis
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- Fall '18
- Cesar M
- Brachial plexus, Muscles of the upper limb