Arm Muscles

REMEMBER - actions are done below the joint that they act on

  • Supraglenoid tubercle - above glenoid cavity

  • Infraglenoid tubercle - under glenoid cavity

  • Radial groove - on the posterior side of the humerus

  • Coronoid fossa - anterior side dip

    • Accommodate coronoid process when flexing

  • Olecranon fossa - posterior side dip

    • Accommodate olecranon process when extending

  • Makeup of the condyle - capitulum and trochlea

  • Capitulum - Anterior condyle visible

  • Trochlea - Posterior condyle visible

  • Styloid Process - tip of the radius and ulna

  • Radius - Wider at the bottom

  • Ulna - Wider at the tip

  • Radial tuberosity - ridge on the radius

  • Ulnar tuberosity - ridge on the ulna

  • Radial notch - articulates with the radius

  • Coronoid process - bumpy projection out of the ulna

  • Trochlear notch - part of the ulna to connect to trochlea

  • Olecranon - posterior ulna sticking out

  • Humeroradial joint (hinge joint) - head of radius with capitulum

    • Flexion and extension

  • Humeroulnar joint (hinge joint) - trochlear notch with trochlea

    • Flexion and extension

  • Proximal radioulnar joint (pivot joint) - head of radius with radial notch

    • Radius and ulna look twisted in pronated position

  • Intermuscular septa - fascia separating anterior and posterior arm

  • Biceps brachii - superficial arm, two heads - Don’t attach to the humerus!

    • Long head (lateral) - Supraglenoid tubercle of scapula to radial tuberosity/bicipital aponeurosis

    • Short head (medial) - Coracoid process of scapula to radial tuberosity/bicipital aponeurosis

    • Actions - Flex arm and forearm (when in supinated position, chin ups), resists inferior displacement, supinate forearm 

    • Innervation - Musculocutaneous nerve

  • Coracobrachialis - Deeps to bicep brachii

    • Coracoid process to medial middle humerus

    • Action - Flex and adduct arm/glenohumeral joint

    • Innervation - Musculocutaneous

  • Brachialis - Deep to biceps brachii

    • Bottom half of humerus to coronoid process/ulnar tuberosity

    • Action - Chief flexor at elbow!

    • Innervation - Musculocutaneous nerve

  • Musculocutaneous nerve pathway - Lateral cord, pierce through coracobrachialis, then deep to biceps brachii and superficial to brachialis, turns into lateral cutaneous nerve

    • Innervation - biceps brachii, brachialis, coracobrachialis

  • Triceps 

    • Long head - Infraglenoid tubercle to olecranon process

      • Crosses shoulder joint, so it extends shoulder joint

    • Lateral head - Superior radial groove to olecranon process

    • Medial head - shorter, inferior radial groove to olecranon process

    • Actions - Extend at elbow joint/forearm

    • Innervation -  Radial nerve 

  • Quadrangular space

    • Bounded by teres minor/major, triceps brachii long and lateral head

    • Axillary nerve with posterior circumflex artery

  • Triangular interval

    • Bounded by teres major, triceps brachii long and lateral head

    • Radial nerve and deep brachial artery

  • Travel buddies - Brachial artery with median nerve

  • Radial nerve pathway - posterior cord, triangular interval, radial groove, in between lateral and medial triceps brachii head,  supinator, posterior interosseous nerve