Prelab Images - Flexor Compartment of the Forearm, Superficial Hand, and Elbow Joint

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. Review the bony landmarks. (Play movie)

The previously examined features of the humerus are seen in plates N420 or TG2-03 and N421 or TG2-03. The previously examined features of the radius and ulna are seen in plates N436 and N439 or TG2-04. The supinator crest of the ulna is not labeled, but it is where the supinator muscle attaches to the ulna in plates N450 or TG2-21, N451 or TG2-22, and N440. The posterior border of the ulna is not labeled in plate N439 or TG2-04, but it looks similar to the anterior border of the ulna that is labeled in this plate. The interosseous crest of the ulna is where the interosseous membrane attaches to it; this is also unlabeled in plate N439 or TG2-04. The interosseous crest of the radius is also unlabeled in plate N439 or TG2-04. The dorsal radial tubercle and grooves for tendons are labeled on the radius in plate N439 or TG2-04. The metacarpals and proximal, middle, and distal phalanges are seen in plates N452 or TG2-31 and N456 or TG2-32.

Step 2. 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.

Step 6. On flexor side of forearm, separate and dissect the various muscular layers and trace the median and ulnar nerves. (Play movie)

Plate N446 or TG2-23 shows the superficial layer of flexor forearm muscles. Plate N450 or TG2-21 and N451 or TG2-22 show the origin and insertions of each muscle. Plate N475 or TG2-27A or TG2-27B shows the median nerve passing between the superficial and deep heads of pronator teres. Plates N446 or TG2-23, N460 or TG2-34, and N461 or TG2-28 show the tendons of flexor carpi radialis, palmaris longus, and flexor carpi ulnaris passing into the wrist. Plate N451 or TG2-22 shows the ulnar and humeral origin of flexor carpi ulnaris and plate N476 or TG2-49 shows how the ulnar nerve will pass between these two heads as it makes its way from behind the medial epicondyle into the forearm. Using the median nerve as a guide, you can cut through and reflect the superficial head of pronator teres to reveal the course of the median nerve and the deep head of pronator teres (N447 or TG2-24). Plate N447 or TG2-24 shows the flexor digitorum superficialis, which will be revealed after pushing the superficial layer of muscles aside. The fibrous arch is visible in plate N447 or TG2-24. Plate N461 shows the arrangement of tendons at the wrist. Plate N450 or TG2-21 shows the origin and insertion of this muscle. Cutting through the radial origin of this muscle beginning at the fibrous arch will allow you to push it medially to expose the deepest layer of muscles, which are seen in plate N448 or TG2-25 (flexor pollicis longus, flexor digitorum profundus, and pronator quadratus). The anterior interosseous nerve is a branch of the median nerve and can be seen in plates N475 or TG2-48 and N448 or TG2-25. The anterior interosseous artery is also shown in plate N448 or TG2-25. Plate N434 or TG2-19 shows the brachial artery dividing into radial and ulnar arteries. The course of the radial artery continues in plate N447 or TG2-24 and it gives off the superficial palmar branch in plate N466 or TG2-37A and TG2-37B. The radial artery then curves around to the dorsum of the hand and runs through the anatomical snuff box in plates N465 or TG2-40 and N445 or TG2-41 before piercing the first dorsal interosseous muscle. The radial pulse point can be observed in plate N446 or TG2-40 and N461, but it is not labeled. Plate N448 or TG2-25 shows the ulnar artery giving off the common interosseous artery. The posterior interosseous artery branches from the common interosseous artery and plunges deep into the arm to appear on the posterior side in plate N445 or TG2-30. The anterior interosseous artery branches from the common interosseous artery; and its course is seen in plate N448 or TG2-25. The ulnar artery continues down the forearm in plate N448 or TG2-25 and its termination in the hand can be seen in plate N464 or TG2-37A and TG2-37B. The pulse point of the ulnar artery can be seen in plate N461 or TG2-37A, but is unlabeled. Plate N434 or TG2-19 shows the collateral circulation of the elbow. Plates N448 or TG2-27 and N475 or TG2-48 should give you a good idea of the path of the median nerve. Plate N461 or TG2-36 shows the location of the median nerve at the wrist and plate N448 or TG2-25 shows the anterior interosseous artery. The ulnar nerve is seen in plates N447 or TG2-24, N448 or TG2-25, and N476 or TG2-49. The dorsal cutaneous branch of the ulnar nerve is shown in plates N476 or TG2-39 and N468 or TG2-40. The ulnar nerve at the wrist is featured in plate N461 or TG2-38. The cross sections of the forearm in plate N449 or TG2-28B and TG2-28C may help you trace these nerves. Plates N472 or TG2-33 and N481 or TG2-51A or TG2-51B show the cutaneous distribution of the nerves.

Step 7. Open the elbow by removing the anterior and posterior capsules. (Play movie)

Plate N438 or TG2-43 shows the elbow joint. Plates N431 or TG2-17 and N432 or TG2-18 show muscles spanning the elbow joint, which must be reflected away from the joint as well as the insertion of the biceps tendon on the radial tuberosity. Plate N438 or TG2-43 identifies the radial collateral, ulnar collateral, and anular ligaments. To dissect the elbow joint, leave these ligaments intact and remove the capsule. This should look like plate N438 or TG2-43. The interosseous membrane is shown in plate N439 or TG2-43. The distal radioulnar joint and its articular disc is in plate N454 or TG2-44A and N455 or TG2-44B and TG2-44C. See the joint learning module for its movement.

 

Updated: 25 Oct 2011