Dissector Answers - Superficial Limbs & Posterior Shoulder
OBJECTIVES and EXPLANATIONS:

1. Identify and demonstrate the areas of distribution of the major cutaneous nerves of the upper limb. (W&B 102-106, N 429,430,431, 432,474,477, 478, 479, 480, 481, 482)

Images from "Anatomy of the Human Body" by Henry Gray are provided by:

The major cutaneous nerves of the upper limb:
2. Identify and demonstrate the major superficial veins of the upper limb. (W&B 101-103, N 189,479, 480,483)

Arising from the dorsal venous network (arch) on the dorsum of the hand are the two most important superficial veins: the cephalic and basilic veins. The cephalic vein ascends along the lateral aspect of the forearm. (This side of your arm is considered "cephalic" because the limbs develop projecting laterally from the body, with the lateral side closest to the head. Or, you can remember that the cephalic side is on the side of your thumb, the digit you stick in your cephalic orifice (mouth) when you are a baby.) Upon completing its ascent, the cephalic vein crosses through the deltopectoral groove before diving deep through the fascia and joining the axillary vein. The basilic vein ascends on the medial aspect of forearm and pierces the deep fascia of the inferior arm. It ascends to unite with the paired brachial veins, forming the axillary vein. The cephalic and basilic veins are connected by the median cubital vein in the cubital fossa.
3. Describe the subcutaneous venous drainage of the lower limb, its relation to the deep veins, and the significance of perforating veins. (W&B 577-579, N 544,545)
The superficial veins of the lower limb begin as the dorsal venous arch of the foot. This dumps into two primary veins:

greater saphenous vein: on the medial side. It receives blood from the dorsal venous arch. The greater saphenous vein then heads north, traveling anterior to the medial malleolus, up the leg, through the knee region on the posterior aspect of the medial condyle of the femur, then turns anteriorly and laterally as it travels up the thigh. The greater saphenous vein travels through the saphenous opening, a passageway in the fascia of the femoral triangle, to drain into the femoral vein. Along its course the greater saphenous vein receives tributaries from the dorsum of the foot, the heel, the front of the leg, and anterior, medial, and lateral portions of the thigh. Also important, right before emptying into the femoral vein, the greater saphenous vein receives the superficial epigastric, superficial circumflex iliac, and superficial external pudendal veins.

lesser saphenous vein: on the lateral side. It runs posterior to the lateral malleolus and up the middle of the back of the leg. It usually pierces the crural fascia about halfway up the leg, running the rest of the way deep to the fascia. In most cases, the lesser saphenous vein terminates in the popliteal vein.

Images from "Anatomy of the Human Body" by Henry Gray are provided by:

4. Describe the lymphatic drainage of the lower limb and areas draining into the superficial and deep inguinal lymph nodes. (W&B 578-580, N 546)
The superficial lymph vessels of the lower limb accompany the superficial veins. They end in the superficial inguinal lymph nodes. From there, most lymph passes directly to the external iliac lymph nodes, but some flows to the deep inguinal lymph nodes. The deep lymphatic vessels accompany the deep veins, and drain directly into the deep inguinal lymph nodes.
5. Identify the major cutaneous nerves of the lower limb, their source, and the areas they innervate. (W&B 580-583, N 540, 541, 542, 544)
The figures on W&B 581 and N 543 are handy views of dermatomes of the lower limb, though they don't technically show how the fibers get there, i.e., via which nerve. But, if you check out W&B 582, and N 540, 542, 544, or check out the images below, you'll get the idea.

Images from "Anatomy of the Human Body" by Henry Gray are provided by:
Images from "Anatomy of the Human Body" by Henry Gray are provided by:

knee and above:

below the knee:

6. Define the regional deep fascias of the lower limb and their regional specializations. (W&B 584-588, 608-610, N 509,522,530)
The deep fascia of the lower limb is called the fascia lata in the thigh and the crural fascia in the leg. These have the following specializations:

fascia lata: crural fascia: In the ankle region, the crural fascia thickens to form retinacula that hold tendons close to the bone, creating a sort of pulley sytem. They are listed here:
7. Identify and demonstrate the posterior shoulder muscles and associated rotator cuff muscles. Give their general functions and nerve supply. N 425, 426, 427
Muscle Origin Insertion Action Innervation
deltoid lateral one-third of clavicle, acromion, lower lip of the crest of the spine of the scapula deltoid tuberosity of the humerus abducts arm; anterior fibers flex & medially rotate arm; posterior fibers extend & laterally rotate arm axillary nerve (C5,6) from posterior cord of brachial plexus
teres major dorsum of the inferior angle of scapula crest of lesser tubercle of humerus adducts arm, medially rotates arm, assists in arm extension lower subscapular nerve (C5,6) from the posterior cord of the brachial plexus

Rotator Cuff:

Muscle Origin Insertion Action Innervation
supraspinatus supraspinatus fossa greater tubercle of humerus (highest facet) abduct arm (initiate abduction) suprascapular nerve (C5,6) from superior trunk of brachial plexus
infraspinatus infraspinatus fossa greater tubercle of humerus (middle facet) laterally rotate arm suprascapular nerve
teres minor upper 2/3 of the lateral border of the scapula greater tubercle of humerus (lowest facet) laterally rotates arm axillary
subscapularis medial two-thirds of costal surface of scapula (subscapular fossa) lesser tubercle of humerus medially rotates arm; assists extension of arm upper and lower subscapular nerves (C5,6)

The rotator cuff is a musculotendinous cuff around the glenohumeral joint. To remember the muscles that participate in it, use the mnemonic "SITS": Supraspinatus, Infraspinatus, Teres minor, Subscapularis. The tendons of these muscles reinforce the articular capsule of this joint. Their main purpose is to hold the head of the humerus in the glenoid cavity during movement of the arm. (The rotator cuff's vulnerable aspect is that it does not effectively prevent dislocations of the shoulder if the arm is pulled straight down, since it is incomplete inferiorly. Otherwise, the most common way to damage the cuff is seen in the example of a hockey player who collides into a wall with her arm stuck straight out in front of her to absorb the shock.)
8. Identify and demonstrate the regional blood supply to the shoulder. (W&B 115-118, N 426, 427)
The axillary artery is the primary source of blood to the region. (It continues as the brachial artery, which supplies the upper limb.) The artery proper, including all of its branches, will be given complete treatment with the axilla. For now, there are a few important concepts to begin thinking about.

Two branches of the third part of the axillary artery are the anterior and the posterior circumflex humoral arteries. These form a circle of blood flow around the surgical neck of the humerus. The posterior is larger than the anterior, and accompanies the axillary nerve through the quadrangular space.

The important arteries that form anastomoses around the scapula are the dorsal scapular, suprascapular and subscapular, and, one of its branches, the circumflex scapular artery. A visual must be consulted to truly get the picture, however, the significance of the anastamoses of the shoulder is that if one of these arteries is occluded there are other routes through which the blood supply can reach the area, thereby avoiding ischemia. Also, surgical ligatures can be placed on the suprascapular, axillary or subscapular arteries without damaging the muscles of the shoulder.
Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless. The Femur - The Muscles and Fascia of the Thigh - The Veins of the Lower Extremity, Abdomen, and Pelvis - The Arteries of the Lower Extremity - Surface Anatomy of the Lower Extremity - Surface Markings of the Lower Extremity

QUESTIONS and ANSWERS:

9. Identify the dorsal digital veins and intercapitular veins, what do these do?
Dorsal digital veins drain the dorsal cutaneous aspect of the fingers. There are two per finger. Intercapitular veins are found between the knuckles (heads of the metacarpals). They drain the fingers and palm to the dorsal side of the hand. N 480
10. Does the basilic vein perforate the brachial fascia in your cadaver? As you traced the basilic vein did you find accompanying nerves? What are these?
The basilic vein normally perforates the brachial fascia above the medial epicondyle, or even as high as mid-arm. Distally near the hand, the vein is accompanied by the dorsal branch of the ulnar nerve. As the vein ascends it is accompanied by the anterior and posterior branches of the medial antebrachial cutaneous nerve. N 479
11. Where does the cephalic vein penetrate the deep fascia?
As mentioned above, the cephalic vein penetrates the deep fascia after it has traversed the deltopectoral groove at the clavicle. N 424
12. Does the cephalic vein extend into the arm?
Of course, though in some arms it may be very small. N 479,480
13. What is the course and direction of the median cubital vein? Look at other arms to determine pattern. What are other variations?
Median cubital vein shunts blood from cephalic vein obliquely across the cubital fossa to reach the basilic vein. There is often a median antebrachial vein lying on the anterior forearm that splits to drain to both cephalic and basilic veins at the cubital fossa.
14. Trace the superficial branch of the radial nerve into the hand and identify its dorsal digital branches and their areas of distributions. Do any branches communicate with branches of the ulnar nerve?
The two nerves usually communicate on the dorsum of the hand. N 480,481
15. Do you see accessory tributaries or varicosities of the superficial veins?
There is usually a fairly large accessory saphenous vein draining the medial thigh, in addition to numerous smaller accessory tributaries. As well, the superficial veins communicate with the deep veins of the lower limb via perforating veins through the deep fascia of the lower limb. These perforating veins have valves that direct the blood superficial to deep as the result of limb motions and muscle contractions. However, the valves may become incompetent, resulting in retrograde blood flow from deep to superficial. The superficial veins may become dilated and torturous, especially in the leg.
16. To what vein does the greater saphenous vein drain?
The greater saphenous vein drains to the femoral vein, through the saphenous hiatus. N 544
17. From what regions do the superficial inguinal lymph nodes receive lymph?
The superficial inguinal lymph nodes receive lymph from the superficial tissues of lower abdominal wall, the external genitalia, the perineum, the buttocks, and the lower limb. N 546
18. Where do the superficial inguinal lymph nodes drain?
They drain primarily to external iliac lymph nodes, but some drain to the deep inguinal lymph nodes.
19. Where would you find the deep inguinal lymph nodes?
The deep inguinal lymph nodes, approximately three in number, lie within the femoral canal, within the femoral sheath, medial to the femoral vein. N 546
20. What is the distribution of the femoral branch of genitofemoral nerve?
This small branch of the genitofemoral nerve within the abdomen passes beneath the inguinal ligament on the external iliac artery. It innervates a small area of skin on the upper medial thigh. N 544
21. From what are the cutaneous nerves of the anterior thigh derived?
The lateral femoral cutaneous nerve is from the lumbar plexus, specifically L2 and L3. The anterior femoral cutaneous nerves are branches of femoral nerve. The femoral branch of genitofemoral nerve is from the lumbar plexus, specifically L1 & L2. N 526
22. What is the source of the saphenous nerve?
The femoral nerve is the source of the saphenous nerve. N 545
23. What nerves accompany the lesser saphenous vein?
The medial sural cutaneous nerve and sural nerve accompany the lesser saphenous vein. N 538
24. Where does the lesser saphenous vein disappear? Where does it terminate?
The lesser saphenous vein pierces the popliteal fascia covering the popliteal fossa at the back of the knee. In that area it drains into the popliteal vein. N 545
25. How is the sural nerve formed?
The sural nerve is formed from fibers contributed by both the tibial and common fibular nerves. N 545
26. Where does the sural nerve distribute and by what name?
It distributes to the posterolateral aspect of the lower leg, the ankle, and the heel. Its continuation on the lateral side of the foot, all the way down to the little toe, is called the lateral dorsal cutaneous nerve. N 545
27. Does the supraspinatus muscle use the fascia spanning the area from the spine to the superior border of the scapula?
Yes, it arises from the dense fascia covering the muscle. It arises from the medial 2/3 of the walls of the fossa.
28. Does the subacromial bursa continue laterally deep to the deltoid muscle? Significance?
The subacromial bursa is a "synovial bursa" situated directly under the deltoid muscle, between it and the supraspinatus tendon and the joint capsule. It has an extension which runs deep to the acromion and the coracoacromial ligament. The bursa facilitates the movement of the deltoid muscle over the joint capsule and tendons. N 423
29. To how much of the supraspinous fossa does the supraspinatus muscle attach?
Although the supraspinatus muscle fills the supraspinous fossa, it arises primarily from the medial aspects of this fossa. N 426
30. How are the suprascapular artery, vein, and nerve related to the scapular notch?
The suprascapular notch is bridged by the superior transverse scapular ligament. The suprascapular nerve passes under the ligament. The suprascapular artery and vein pass over it. (The navy goes under the bridge, the army goes over.) N 426,427
31. How much of the fossa is used for the infraspinatus muscle attachment?
The infraspinatus muscle arises from the whole of the infraspinatus fossa except its lateral 1/4, and from the overlying infraspinatus fascia and the intermuscular septa. N 425, 426
32. Trace the nerve, artery, and vein from the supraspinatus to the infraspinatus fossa around the notch of the neck of the scapula. Does the artery terminate in the infraspinatus muscle?
Semantically, the artery comes to an end, but really it enters into the anastomoses of the shoulder region, specifically with the circumflex scapular artery. N 426,427
33. Is the teres minor muscle separated or fused with the lateral border of the infraspinatus?
The teres minor muscle is often totally fused with the lateral border of the infraspinatus muscle. N 425
34. For the question about the rotator cuff, see the treatment of the theme above under the lab objectives.

See #7 above. N 421,426,429,430
35. What are the boundaries of the quadrangular space? What does it transmit?
The borders of the quadrangular space are: The space transmits the axillary nerve and the posterior circumflex humeral artery. N 426
36. Find the circumflex scapular artery in the triangular space. Is there an open anastomosis between it and the suprascapular artery?
There is usually an open anastomosis between the circumflex scapular artery and the suprascapular artery. N 426,427
37. Identify the circumflex scapular artery. What does it supply? Does it anastomose with the suprascapular artery?
The triangular space transmits the circumflex scapular artery. This vessel feeds the muscles of the dorsum of the scapula and participates in the anastomoses described above. It certainly does anastomose with the suprascapular artery. N 426,427
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