Lateral border - Margo lateralis
The lateral border runs from the back part of the greater tubercle to the lateral epicondyle, and separates the anterolateral from the posterior surface. Its upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the Teres minor, and below this giving origin to the lateral head of the Triceps brachii; its center is traversed by a broad but shallow oblique depression, the radial sulcus (musculospiral groove). Its lower part forms a prominent, rough margin, a little curved from behind forward, the lateral supracondylar ridge, which presents an anterior lip for the origin of the Brachioradialis above, and Extensor carpi radialis longus below, a posterior lip for the Triceps brachii, and an intermediate ridge for the attachment of the lateral intermuscular septum.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
General Anatomy > Bones; Skeletal system > Appendicular skeleton > Bones of upper limb > Free part of upper limb > Humerus > Shaft of humerus; Body of humerus > Lateral border