arm and forearm

Axilla boundaries

• Apex → middle 1/3 of clavicle

• Base → inferior to rib 5

Axilla contents

• Muscles

  • Biceps brachii

  • coracobrachialis

• Nerves

  • Cords of brachial plexus

  • Pectoral nerve (med and lat) - affects pecs

  • Subscapular nerve - affects subscapularis and teres major

  • Long thoracic nerve - affects serratus anterior

• Vessels

  • Axillary vein - large and superficial

  • Axillary artery - palpable

  • Lymphatics - axillary lymph nodes drain into apical node

Compartments of the arm

• Anterior

  • 3 Flexors innervated by musculocutaneous nerve

    • Biceps brachii

      • Simple flexor/ number 1 supinator

    • Brachialis

      • Main flexor of the forearm

    • Coracobrachialis

      • flexes and adducts arm

• Posterior

  • 1 extensor innervated by radial nerve

    • Triceps brachii

      • Main extensor of arm/forearm

Forearm

• Radius and ulna are connected by interosseous membrane which acts as muscle attachment and binds forearms together

Elbow arthrology

• Hinge synovial - ginglymus

  • Diarthrosis

    • flexion and extention, supination and pronation

  • Carrying angle of 170 degrees

  • Humerus + ulna = flex and extend

  • Humerus + radius = flex, extend and rotate

  • Radius and ulna = rotate

• Contains 3 major ligaments

  • annular ligament

  • radial ligament

  • ulnar ligament

• Contains olecranon bursa

  • Student’s elbow = bursitis

Radioulnar Joints

• Proximal

  • Head of radius fits against radial notch of ulna

  • Pivot synovial → trocoid

    • only rotational movement allowed

  • Annular ligament secures head of radius

    Muscles moving the joint

    • Supination → supinator

    • pronation → pronator teres + pronator quadratus

  • transient subluxation of radial head due to problems with the annular ligament

• Distal

  • Ulnar head fits with ulnar notch of distal radius

  • pivot synovial joint

  • Triangular ligament (articular disc)

    • Radius (broad); styloid process of ulna

  • Anterior and posterior ligaments

    • Weak transverse

  • Muscles moving same as proximal joint

Muscles of forearm

• Anterior/flexors

  • All median nerve except for the flexor carpi ulnaris and digitorum profundus

  • Superficial groups - cross elbow joint - 5 muscles

    • have common origin at the common flexor tendon at the medial epicondyle

      • Pronator teres

      • palmaris longus

      • flexor carpi radialis

      • flexor carpi ulnaris

      • flexor digitorum superficialis

  • Deep group - dont cross elbow - 3 muscles

    • Flexor digitorum profundus

      • innervated by median and ulnar

    • Flexor pollicis longus

      • flexes distal phalanx of thumb

    • Pronator quadratus

      • deepest forearm muscle

• Posterior/ extensors

  • All innervated by the radial nerve

  • covered by the extensor retinaculum

  • Has synovial tendon sheaths on fingers

  • extensor expansions

  • Superficial groups - 7

    • Brachioradialis

      • only flexor post compartment

    • Extensor carpi radialis longus

    • Extensor carpi radialis brevis

    • Extensor digitorum → claw hand

    • Extensor digiti minimi

    • Extensor carpi ulnaris

    • Anconeus

      • part of triceps brachii

  • Deep extensor group

    • Abductor pollicis longus

    • Extensor pollicis longues

    • Extensor pollicis brevis

    • Extensor indices

    • Supinator

Anatomical snuff box

• Boundaries

  • Tendons of:

    • Extensor pollicis longus

    • Extensor pollicis brevis

    • Abductor pollicis longus

  • Contains the

    • Radial artery

    • Radial styloid process

    • scaphoid

    • trapezium