We’ll remove the profundus tendon for a moment. Over the proximal phalanx, the superficialis tendon splits into two halves, which pass around the profundus tendon. Just before reaching the MP joint, the superficialis and profundus tendons of each finger enter the flexor tendon sheath together. Over the proximal phalanx, the superficialis tendon splits into two halves. For now we’ll remove them to simplify the picture. Just as the flexor tendons emerge from the carpal tunnel, the four profundus tendons give rise to these four intrinsic muscles, the lumbricals.
Before we follow the superficialis and profundus tendons into the hand, we’ll bring the forearm to the upright position.Īs the flexor tendons pass through the carpal tunnel, they’re all enfolded within this common synovial sheath which extends into the palm of the hand. The four separate tendons of flexor digitorum superficialis are bundled together as they enter the carpal tunnel. Between the two heads there’s a gap, which the median nerve and the ulnar artery both pass through. Its radial head arises from this long oblique line on the radius. The humero-ulnar head arises, as part of the common flexor tendon, from the medial epicondyle of the humerus, and also from the adjoining ulna. It has two heads of origin, a radial head and a humero-ulnar head. Now let’s add the superficial finger flexor, flexor digitorum superficialis to the picture. It’s flexor pollicis longus, the long thumb flexor. This adjoining muscle we’ll see later on. Here are its four tendons, entering the carpal tunnel. It arises from the anterior and medial surface of the ulna, and from the interosseous membrane. Here’s the deep finger flexor, flexor digitorum profundus. Flexion of the fingers is produced by two long muscles, flexor digitorum profundus, and flexor digitorum superficialis.