Prelab Images - Extensor Compartment of the Forearm, Deep Hand, Wrist and Hand Joints

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Open the hand, look at creases, and skin the palm (do not cut the recurrent branch of median n.). (Play movie) and Step 2. Reflect the palmar aponeurosis distalward and identify neurovascular structures. (Play movie)

Plates N447 or TG2-24 and N448 or TG2-25 show the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus muscles, which you must cut through to begin the dissection. Cut through them at different places proximally to distally so you will be able to tell which distal muscle piece belongs to which proximal muscle piece. Now you can straighten out the fingers to make the dissection easier. Remove the remaining skin of the hand. The proper and common digital branches of the median and ulnar nerves are labeled in plates N460 or TG2-34 and N466 or TG2-38. They are fairly superficial and can be destroyed if the fingers are not skinned carefully. Looking closely at these plates you can see branches wrapping around to the dorsal side of the hand to innervate the nail beds (N468 or TG2-38 and TG2-40). See plate N472 or TG2-33 for the area of cutaneous distribution for these nerves. Plates N465 or TG2-34 and N466 or TG2-38 show the recurrent motor branch of the median nerve to the thenar muscles. The branch is best found by tracing the median nerve through the carpal tunnel and identifying its recurrent branch hooking around the distal edge of the flexor retinaculum. Plate N459 or TG2-33 shows thenar and hypothenar fascia (unlabeled) and the palmar aponeurosis. Fibrous (synovial) flexor digital sheaths can be seen in plates N460 or TG2-34 and N472 surrounding the tendons in digits 2, 3, and 4. Plate N459 or TG2-33 shows the palmar aponeurosis and its relation to palmaris longus, the palmar carpal ligament, and the flexor retinaculum can be seen in plate N460 or TG2-34. Gaps between transverse fasciculi and the superficial transverse metacarpal ligament can be seen in plate N459 or TG2-33. Plate N460 or TG2-34 shows the palmar aponeurosis being reflected distally as you will reflect it during lab. Plate N464 or TG2-36 shows the carpal tunnel in cross section. Plates N460 or TG2-34 and N464 show the ulnar nerve and artery crossing near the pisiform and dividing into deep and superficial branches. Plate N466 or TG2-37A and TG2-37B shows the superficial ulnar artery forming the superficial palmar arterial arch, which will then give off common palmar digital arteries, which branch to form proper palmar digital arteries. The superficial arch is completed by the superficial palmar branch of the radial artery (N466 or TG2-37A and TG2-37B). The deep branch of the ulnar artery will go on to complete the deep palmar arterial arch with the radial artery. This deep arch gives off palmar metacarpal arteries (N466 or TG2-37A and TG2-37B). The superficial ulnar nerve is seen dividing into common and proper palmar digital nerves in plate N466 or TG2-38 and the proper palmar digital branches can be seen wrapping around to innervate the nail bed in plate N468 or TG2-40. Review plate N472 or TG2-39 for the area of cutaneous distribution. Plates N460 or TG2-34, N465, and N466 or TG2-38 all give similar views of the course of the median nerve. Make sure to follow it under the flexor retinaculum before removing too much fascia of the hand to avoid damaging it. Plate N466 or TG2-38 shows common and proper palmar digital branches of the median nerve (the proper digital branches also send branches to innervate the nail beds like the proper digital branches of the ulnar nerve). See plate N472 or TG2-33 for cutaneous distribution.

Step 3. Examine the muscles of the thenar and hypothenar compartments. (Play movie)

Plate N472 or TG2-34 shows the fibrous digital flexor sheath of the ring finger opened. Plate N472 divides the hand into its spaces (thenar space, central compartment/ midpalmar space, hypothenar space, and adductor-interosseous compartment). Plate N465 or TG2-35 and N464 give views of abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. Plate N465 or TG2-35 also shows adductor pollicis, which is not a thenar compartment muscle. Plate N464 and N472 or TG2-34 shows the tendon of flexor pollicis longus surrounded by the radial bursa. Plate N465 or TG2-35 and N466 or TG2-37 and TG2-38 once again show the recurrent motor branch of the median nerve and the superficial palmar branch of the radial artery forming the superficial palmar arterial arch. Plate N464 and N465 or TG2-35 shows the abductor digiti minimi, flexor digiti minimi (brevis), opponens digiti minimi, and their innervation by the deep branch of the ulnar nerve, which passes deep to these muscles (best seen in plate N465 or TG2-35).

Step 4. Cut the flexor retinaculum and pull the long flexor tendons toward the fingertips. (Play movie)

Plate N464 or TG2-34 shows the flexor retinaculum over the carpal tunnel. After cutting through the flexor retinaculum you should be able to pull the distal pieces of the muscles you cut through in step 1 towards the fingertips. Plates N464 and N472 or TG2-34 shows the tendons of flexor digitorum superficialis and profundus in the carpal tunnel and ulnar bursa. Once again plate N472 or TG2-34 shows a sheath incised longitudinally. Vincula are shown in plate N464 or TG2-41B. Plates N460, N463, and N464 or TG2-41B and TG2-34 feature the lumbrical muscles. Plates N464 and N472 or TG2-31 trace flexor pollicis longus to its insertion (N450 or TG2-21). Plate N464 shows the position of flexor carpi radialis at the wrist and plate N450 or TG2-21 shows its insertion. Plates N466 or TG2-38 and N475 or TG2-48 fully trace the median nerve in the hand. Plates N472 and N465 or TG2-35 show the adductor-interosseous compartment. Plate N464 or TG2-35 shows that adductor pollicis has oblique and transverse heads. The deep palmar arterial arch is shown in plates N465 or TG2-35 and N466 or TG2-37A and TG2-37B.

Step 5. Follow the radial artery through the anatomical snuffbox and through the 1st dorsal interosseous m. (Play movie)

Plate N466 or TG2-37A and TG2-37B (top) shows the radial artery giving off a superficial branch. It then moves to the dorsum of the hand and passes through the anatomical snuff box and gives off a dorsal arterial arch (plate N469 or TG2-41) before piercing the first dorsal interosseous muscle. Plate N466 or TG2-37A and TG2-37B (bottom) shows it then giving off the princeps pollicis artery (will branch to form proper digital arteries of the thumb), radialis indicis artery, and then continuing to form the deep palmar arterial arch. Plate N465 or TG2-35 shows adductor pollicis cut at its origin where you want to cut it to reflect it. You should then be able to dissect the dorsal and palmar interosseous muscles (N465 or TG2-35). Plate N464 or TG2-41B shows how these muscles and the lumbricals insert into the extensor expansion. Plates N466 or TG2-37A and TG2-37B and N469 or TG2-46 should paint a fairly complete picture of the blood supply to the hand. Plates N465 or TG2-48, N466 or TG2-49 and TG2-50, N472, N475 or TG2-52, and N459 organize the sensory and motor innervation to the hand.

 

 

Updated: 31 Oct 2011