Those running through the radial groove
- Radial nerve. Runs shallowly just posteriorly below the deltoid tuberosity. It runs obliquely in a spiral downward and anteriorly on the posterolateral aspect of middle of humerus.
- This groove is often obscured, but it separates the attachment (origin) of the two heads of the triceps brachii. That is, the lateral head of the triceps muscle attaches to the (upper) lateral side of the groove, and the medial head of the triceps muscle to the (lower) medial side.