Medial surface - Facies medialis
The medial surface (internal surface) is broad and concave above, narrow and convex below. Its upper three-fourths give origin to the Flexor digitorum profundus; its lower fourth is subcutaneous.
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 > Ulna > Shaft of ulna; Body of ulna > Medial surface