Lab Manual - Superficial Limbs & Posterior Shoulder

Lab Manual - Superficial Limbs & Posterior Shoulder

Assignments:

Complete the learning module entitled Movements of the upper limb.
Read the Lab Manual and Dissector Answers, view the Lab Video, and review the Prelab Images.
Read Woodburne & Burkel: 94-114, 575-585

Objectives:

Upon completion of this session, the student will be able to:

Identify and demonstrate the areas of distribution of the major cutaneous nerves of the upper limb.
Identify and demonstrate the major superficial veins of the upper limb.
Describe the subcutaneous venous drainage of the lower limb, its relation to the deep veins and the significance of perforating veins.
Describe the lymphatic drainage of the lower limb and areas draining into the superficial and deep inguinal lymph nodes.
Identify the major cutaneous nerves of the lower limb, their source and the areas they innervate.
Define the regional deep fascias of the lower limb and their regional specialization such as iliotibial tract, etc.
Identify the posterior shoulder muscles and associated rotator cuff muscles. Give their general functions and nerve supply.
Identify and demonstrate the regional blood supply of the posterior shoulder.

Summary of Dissection Procedure:

Review the bony landmarks of the upper limb.
Skin the upper limb (except the palm of the hand).
Find the superficial veins and cutaneous nerves of the upper limb.
Skin the anterior surface of the lower limb, preserving the cutaneous vessels and nerves.
Trace the greater saphenous vein from the foot upward to its termination.
Clean the subcutaneous tissue from the anterior surface of the lower limb and identify the cutaneous nerves and specializations of the fascia.
Turn the body over, and skin the posterior surface of the lower limb, preserving the cutaneous vessels and nerves.
Trace the lesser saphenous vein from the foot upward to its termination.
Clean the subcutaneous tissue from the posterior surface of the lower limb and identify the cutaneous nerves and specializations of the fascia.
Reflect deltoid muscle from acromion and spine of scapula.
Saw off acromion and reflect supraspinatus muscle.
Reflect infraspinatus from the medial border of scapula toward shoulder and find nerves and vessels beneath.
Dissect the teres minor and major muscles.

Procedure:

1. Review the bony landmarks of the upper limb. (Play movie; View images: N 419, 420, 421, 439)

On a skeleton, review the following bony features of the upper limb: on the humerus, the head and anatomical and surgical necks, greater and lesser tubercles and their crests, the intertubercular or bicipital groove, deltoid tuberosity, and medial and lateral epicondyles; the styloid processes of the radius and ulna; on the scapula, the supraspinous and infraspinous fossae, scapular notch, and acromion process; and the clavicle.

2. Skin the upper limb (except the palm of the hand). (Play movie; View images: N 428)

With the body on its back, skin the upper limb except the palm of the hand. Leave the superficial fascia intact.

3. Find the superficial veins and cutaneous nerves of the upper limb. (Play movie; View images: N 189, 418, 429, 430, 431, 432, 474, 476, 477, 478, 479, 480, 481, 482, 483)

Superficial veins. To demonstrate the veins, begin on the posterior side of the wrist and hand where the subcutaneous tissue is the thinnest and pick up any cutaneous vein, trace it toward the digits. Note that all veins are interconnecting, forming plexiform networks. Identify dorsal digital veins, intercapitular veins (what do these do? ), dorsal metacarpal veins. The dorsal venous arch and network of the hand provides communication between adjacent dorsal metacarpal veins. The patterns of this plexus vary. Note this arrangement on the dorsum of your own and your partners' hands. Trace the ulnar continuation of this plexus as the basilic vein (or plexus of veins) along the ulnar border of the forearm. It continues to the arm and normally perforates the deep (brachial) fascia about 5 cm above the medial epicondyle of the humerus. Do not trace beyond this point. Does the vein perforate here in your cadaver? As you traced the basilic vein (plexus) did you find accompanying nerves? What are these? Trace the radial continuation of the dorsal venous network as the cephalic vein (plexus) along the radial border of the forearm and arm. Where does it terminate (perforate the deep fascia)? Does the vein extend into the arm? If not, where and how does it continue? Identify the nerve or nerves accompanying the cephalic vein. Note the anastomosis in the cubital fossa, the median cubital vein. What is its course and direction? Look at other arms to determine pattern. What are other variations? Note the perforating veins which communicate through the antebrachial fascia with deep veins especially one anchoring the median cubital vein.

Venogram of the cutaneous veins

The cutaneous nerves of the forearm and hand are more easily found than those of the back. Each perforates the deep (investing) fascia and enters the subcutaneous tissue at an identifiable location, where it is readily found. They may accompany specific veins or other identifiable structures. The cutaneous nerves of the arm and chest are branches of ventral primary rami of the spinal nerves, as are all subsequent nerves of the upper limb.

Locate, trace and determine area of cutaneous distribution of the following nerves. The lateral antebrachial cutaneous nerve perforates the deep fascia lateral to the tendon of the biceps and accompanies the cephalic plexus of veins. The medial antebrachial cutaneous nerve perforates the deep fascia medial to the tendon of the biceps and accompanies the basilic plexus of veins. The posterior antebrachial cutaneous nerve perforates the deep fascia 5 cm above the lateral epicondyle of humerus. The superficial radial nerve perforates the deep fascia along the radial border of forearm at approximately the junction of the middle and distal thirds of the forearm and accompanies parts of the cephalic venous plexus. Trace into the hand and identify its dorsal digital branches and their area of distribution. Do any branches communicate with branches of the ulnar nerve?

Locate the dorsal cutaneous branch of the ulnar nerve as it enters the subcutaneous tissue just distal to the ulnar styloid process. Trace distribution of its dorsal digital branches. Compare with other hands for variations in patterns.

4. Skin the anterior surface of the lower limb, preserving the cutaneous vessels and nerves. (Play movie; View images: N 491, 544)

Skin the anterior surface of the lower limb. Remove the skin of the lower abdominal wall, 5cm superior to the groin crease and the iliac crest. The groin crease lies parallel to the inguinal ligament (which lies along a line projected from the anterior superior iliac spine to the pubic tubercle). Identify the inguinal ligament, but do not dissect through the superficial fascia superior to it. At the ankle and on the dorsum of the foot, the subcutaneous tissue is thin. Use great care here and watch for cutaneous nerves and veins.

5. Trace the greater saphenous vein from the foot upward to its termination. (Play movie; View images: N 262, 265, 266, 408, 545, 546)

Locate the dorsal venous arch in the foot and trace it to the greater saphenous vein. Note specifically its relationships to the medial malleolus and the medial epicondyle. In the thigh its continuation may be found in several layers of the subcutaneous tissue. Note its plexiform arrangement. Do you see accessory tributaries or varicosities? Trace it to the saphenous opening in the thigh and identify the superficial epigastric, superficial circumflex iliac and superficial external pudendal veins as they join the greater saphenous vein. To what vein does the greater saphenous drain?

Open the greater saphenous vein at major junctions and examine the arrangement of the valves.

In the subcutaneous tissue of the inguinal area, define the superficial inguinal lymph nodes. From what regions do they receive lymph? Where do they drain? Where would you find the deep inguinal nodes?

6. Clean the subcutaneous tissue from the anterior surface of the lower limb and identify the cutaneous nerves and specializations of the fascia. (Play movie; View images: N 493, 496, 497, 499, 500, 506, 540, 542, 544, 546)

Trace the following nerves within the subcutaneous tissue of the anterior thigh: lateral femoral cutaneous, anterior femoral cutaneous; what is the distribution of the femoral branch of genitofemoral nerve? From what are these derived?
On the anterior surface of the leg locate and trace the saphenous nerve and its infrapatellar branches (accompanies the greater saphenous vein). Source of nerve? Identify the superficial fibular (peroneal) nerve; trace it, consider its source and outline its distribution to the foot. The terminal end of the deep fibular (peroneal) nerve is found between the great and second toe. Map out areas of distribution for each nerve identified.

Now clear the remainder of the superficial fascia from the anterior surface of the lower limb and dorsum of the foot. Examine the deep fascia and define the fascia lata and the iliotibial tract. Carefully examine the arrangement of fascia lata in the formation of the saphenous opening.

Define the crural fascia and the dorsal fascia of the foot.

7. Turn the body over, and skin the posterior surface of the lower limb, preserving the cutaneous vessels and nerves. (Play movie; View images: N 547)

Turn the body over (prone position). Skin the posterior surface of the lower limb. Watch for cutaneous nerves and veins.

8. Trace the lesser saphenous vein from the foot upward to its termination. (Play movie; View images: N 501, 547)

Beginning on the lateral side of the foot, trace the lesser saphenous vein behind the lateral malleolus and along the posterior side of the leg. Look for small branches of the lesser saphenous vein perforating the crural fascia to join the deep veins. What nerves accompany the lesser saphenous vein? Where does the vein disappear and where does it terminate?

9. Clean the subcutaneous tissue from the posterior surface of the lower limb and identify the cutaneous nerves and specializations of the fascia. (Play movie; View images: N 496, 499, 501, 502, 541, 542, 545)
The posterior femoral cutaneous nerve runs down the midline of the back of the thigh deep to the fascia lata. Cut vertically through the fascia lata on either side of the midline on the posterior side of the thigh, locate the nerve (which usually clings to the underside of the fascia), and then trace it toward the buttock. Identify its inferior cluneal and perineal branches.
In the calf, locate the lateral sural cutaneous nerve, medial sural cutaneous nerve (with lesser saphenous vein), and sural nerve (how formed? where does it distribute and by what name? ).

10. Reflect deltoid muscle from acromion and spine of scapula. (View images: N 420, 421, 424, 425, 426, 427, 429, 430)

Remove the subcutaneous tissue from the dorsal surface of the deltoid and other scapular muscles.

Review the anatomy of the trapezius, latissimus dorsi, rhomboid and levator scapulae muscles.

Deltoid muscle. Carefully remove the investing fascia from the posterior half of the deltoid muscle revealing its origin, insertion, and posterior border. Note the heavy fasciculation and the differences between the central (multipennate) and posterior (parallel) fibers.

CT of the deltoid muscle

Reflect the muscle by cutting its origin from the spine of the scapula and lateral border of the acromion and reflect it as far laterally as possible. Leave the anterior portion of the muscle intact. Carefully probe in the underlying fat and connective tissue to locate the axillary nerve and the posterior circumflex humeral artery and vein emerging from the quadrangular space to enter the deltoid. The major trunks of these vessels and nerve appear on the medial side of the neck of the humerus and encircle the humerus dorsally in a lateral direction, radiating branches into the deltoid muscle. Note that the arteries and veins distribute to all the muscles in the area. In your dissection, clean until you find the major trunks lying on the dorsum of the humerus. Trace all branches.

Supraspinatus muscle. Removal of the insertion of the trapezius muscle from the spine of the scapula and the acromion (leaving it attached to the clavicle) will expose the supraspinatus muscle. Clear any additional fat and loose connective tissue from the muscle. Note that its muscular fascia spans from the spine to the superior border of the scapula and is of greater density medially. Does the muscle use this fascia as an origin? Trace the muscle laterally toward its insertion. Note that it passes deep to the acromion process.

11. Saw off acromion and reflect the supraspinatus muscle. (Play movie; View images: N 421, 423, 425, 426, 427)

Reflect the acromion process forward by cutting through the junction of the spine and acromion with a saw. As you reflect the acromion process, look for a bursa between it and the supraspinatus muscle (subacromial bursa). Does it continue laterally deep to the deltoid muscle (subdeltoid bursa)? Significance? Trace the muscle to its insertion on the humerus. Palpate the greater tubercle. Remove the muscular fascia and then reflect the muscle from the supraspintous fossa beginning at the medial margin of the fossa. Scoop the muscle out, scraping it from its bony attachments. To how much of the supraspinous fossa does it attach? As you reflect the muscle note the suprascapular artery, vein and nerve entering the deep side of the muscle. Locate the scapular notch. How are the suprascapular artery,vein, and nerve related to the scapular notch? Do not completely reflect this muscle to its insertion, as it combines with the capsule of the shoulder joint before it inserts into the greater tubercle of the humerus.

12. Reflect infraspinatus from the medial border of scapula toward shoulder and find nerves and vessels beneath. (Play movie; View images: N 33, 426, 429, 430)

Infraspinatus muscle. Observe the muscular fascia, which attaches to the spine and borders of the scapula and forms a compartment for the muscle. Remove this fascia and determine if it was part of the origin of the infraspinatus. Define the boundaries of the muscle. Reflect the muscle from the infraspinous fossa from medial to lateral as with the supraspinatus. How much of the fossa is used for muscle origin? As you reflect the muscle identify the suprascapular nerve, artery and vein as they enter the deep surface of the muscle and supply it. Trace the nerve, artery, and vein from the supraspinous to the infraspinous fossa through the notch of the neck of the scapula. Does the artery terminate in the infraspinatus muscle? Reflect the muscle only as far laterally as the lateral border of the scapula. Palpate the point of the insertion into the greater tubercle of the humerus.

13. Dissect the teres minor and major muscles. (Play movie; View images: N 421, 424, 426, 427, 429)

Teres minor muscle. Remove the muscular fascia and locate its origin. Is the muscle separate or fused with the lateral border of the infraspinatus muscle? Note the fascial septum between these adjacent muscles. Trace the insertion of the teres minor to the greater tubercle of the humerus, but do not reflect the muscle. Note the sequence of insertions of the three muscles to the greater tubercle. Examine individual facets of insertion on the greater tubercle of the humerus on a skeleton. Carefully clean along the lateral border of the muscle near its insertion and note the nerve to the teres minor from the axillary nerve and the accompanying branches of the posterior circumflex humeral vessels. The supraspinatus, infraspinatus, teres minor, and subscapularis (to be seen later) muscles make up the rotator cuff. What is the significance of this designation?

Teres major muscle. Remove the muscular fascia and locate the origin of the muscle from the inferior angle and the lower third of the lateral border of the scapula. Trace the muscle laterally until it joins the latissimus dorsi. Note that the two muscles travel together and are adherent as they pass to the anterior side of the humerus. Do not trace to their insertions at this time. Remove, carefully, the large masses of fat and connective tissue found in this area. As you trace the teres major laterally you will run into the long head of the triceps brachii overlying it on its dorsal side.

Clean the long head of triceps as it continues upward to attach to the infraglenoid tubercle of the scapula. This muscle forms a boundary between two spaces along the lateral border of the scapula: the triangular space and the quadrangular space. What are the boundaries of the quadrangular space? What does it transmit? Find the circumflex scapular artery in the triangular space and trace its branches and its course into the infraspinatous fossa. Is there an open anastomosis between it and the suprascapular artery? What does it supply? Does it anastomose with the suprascapular artery? What is the significance of this anastomosis? Review the arteries that you have dissected that supply the scapular region. The nerve to teres major will be identified in a later dissection. Consider the actions of the posterior shoulder muscles, concentrating on functional groups.