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- origin:
         lateral head:  superior 1/2 of post. lat. surface of humerus;
         long head:     infraglenoid tuberosity of scapula;
         medial head:
             - inferior 2/3 on posterior surface of the humerus, beginning at the spiral groove;
             - medial head surrounds the radial nerve in the spiral groove;

- insertion: supraposterior surface of the olecranon process of the ulna and deep fascia of the forearm;
- action: extends forearm at the elbow. Longe head aids in adduction and extension of the arm at the shoulder;
- nerve supply:  Radial ,   C7  >   C6 ,   C8 ,   T1
- synergist:       Anconeus ;

- helps form triangular space  & quadrangular space:

- Injury of Triceps:
    - weakness or paralysis of triceps is usually considered of little importance, since gravity will extend elbow passively in most positions that the arm assumes;
    - however, use of the triceps is important for walking with crutches;
    - consider transfer of Brachioradialis muscle from lateral aspect of the elbow and forearm to a position posterior to lateral humeral condyle;
    - should power of the Brachialis muscle be insufficient, added power is  obtained by transferring the ECRL

   
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A Cadaveric Study of Ulnar Nerve Innervation of the Medial Head of Triceps Brachii