Blood vessel
The palmar carpal branch of the radial artery is a small branch of the radial artery which arises near the lower border of the pronator quadratus, and, running across the front of the carpus, anastomoses with the palmar carpal branch of the ulnar artery.
References
This article incorporates text in the public domain from page 594 of the 20th edition of Gray's Anatomy (1918)