The structures passing superficial to the retinaculum include the ulnar nerve and artery, the palmar cutaneous branches of the ulnar and the median nerves, and the tendon of the palmaris longus. The structures passing superficial to the flexor retinaculum It is attached laterally to the scaphoid tubercle and the trapezium, and medially to the pisiform and the hook of the hamate. The flexor retinaculum and the carpal tunnelĪ strong fibrous band called the flexor retinaculum stretches across the concavity of the carpal bones and converts it into a tunnel for the passage of the flexor tendons into the palm. The lateral margin of the palmar apponeurosis is connected to the deep fascia that covers the thenar muscles, whereas the medial edge is connected to the deep fascia that covers the hypothenar muscles. At its base it divides into four slips opposite the heads of the metacarpals of the medial four fingers, which in turn divide into two parts continuing with the fibrous flexor sheath of the digits. Its apex fuses with the flexor retinaculum and receives the insertion of the tendon of palmaris longus.
The palmar aponeurosis is triangular in shape, which forms the central deep fascia of the palm, and fixes the skin of the palm to improve grip, as well as providing protection of the underlying structures.
The deep fascia of the palm is specialised to form the palmar aponeurosis in the palm, the flexor retinaculum at the wrist and the fibrous flexor sheaths in the fingers. It is supplied by the superficial branch of the ulnar nerve. This muscle originates from the flexor retinaculum along with the palmar aponeurosis, the fleshy fibres are inserted into the skin of the hand.
The superficial fascia of the palm contains the palmar cutaneous branch of the ulnar and median nerves, beside palmaris brevis that is used in cupping the palm of the hand in gripping. The skin of the palm, is considered to be thick skin, and has creases that increase the efficiency to grip. The radial nerve also supplies a small area of the skin on the palmar surface to the thenar eminence. The radial nerve supplies the skin of the lateral 2/3 of the dorsal surface of the hand and over the proximal phalanges of the lateral 3½ fingers. The median nerve supplies the skin over the thenar eminence and the central part of the palm, the palmar surface of the lateral 3½ fingers and the dorsal surface of the distal 1/2 of the lateral 3½ fingers. With regards to the cutaneous innervation of the hand, the ulnar nerve supplies the palmar and dorsal surface of the medial third of the hand, simultaneously with the palmar and dorsal aspects of the medial 1½ finger.