- This page refers to triceps brachii in the upper arm. For the
muscle in the leg, see triceps surae. |Function:||Extension of
the elbow| |Origin:|| Long head - infraglenoid tuberosity of
scapula| Lateral head - posterior surface humerus (between Teres
minor and radial groove) Medial head - posterior surface of
humerus below radial groove |Insertion:||Olecranon process of
ulna| |Innervation:||Radial nerve (C7, C8)| |Search for Triceps
in Gray's.| Triceps is palpable posteriorly in the upper arm,
providing the majority of the muscle bulk there. Triceps arises
from three heads - long, lateral and medial. The fibres of the
three heads converge at its tendon, which begins midway along
the muscle's length. It consists of two aponeuroses, one which
is subcutaneous posteriorly in the lower half of triceps, the
other central within the muscle. When all three heads have been
received, the two aponeuroses unite into a single tendon, just
above the elbow. The majority of fibres insert into the
olecranon of the ulna, alt