The "floor" of the tunnel is formed by the transverse carpal ligament. This is a tough fibrous tissue which spans the length of the tunnel, attached at each end to protuberances on the carpals. Click here to see a slide show showing the sites of attachment of the transverse carpal ligament.

Overview
Basic Anatomy (11 pages)
Generic Cause of CTS
Specific Causes of CTS
your path: What is CTS: Basic Anatomy, 5 of 11