The skin and subcutaneous tissue have been removed, as have most of the palmar aponeurosis and the thenar and hypothenar fasciae. (A) The superficial palmar arch is located immediately deep to the palmar aponeurosis, superficial to the long flexor tendons. This arterial arch gives rise to the common palmar digital arteries. In the digits, a digital artery (eg, radialis indicis) and nerve lie on the medial and lateral sides of the fibrous digital sheath. The pisiform bone protects the ulnar nerve and artery as they pass into the palm. (B) Three thenar and three hypothenar muscles attach to the flexor retinaculum and to the four marginal carpal bones united by the retinaculum.