Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Surface anatomy of the back, shoulder, and arm. Fig. 1. The horse’s skeleton in left lateral view. Palpable bony prominences at the shoulder and arm (brachium) are labeled. The sternum is colored yellow so that the superimposition of bones is clearer. The original figure was drawn by Professor Paul Martin; Lehrbuch Anatomie der Haustiere, II. Band, 1. Halfte; 1914, Schickhardt und Ebner, Stuttgart. It has been cropped and, otherwise, modified only slightly. summit of T4 spinous process tuber of spine of scapula manubrium, sternum deltoid tuberosity of humerus olecranon of the ulna position of lateral collateral ligament of elbow joint Fig. 2. Horse is an Akhal-Teke. Photograph (cropped to the area considered here) is from Horse Illustrated, July, 2012. Original uncropped photo is by Katya Druz; www.ARND.NL. Palpable prominences of Fig. 1 are marked by arrows. Fig. 3. Drawn by David Stewart Geary at the Western College of Veterinary Medicine (WCVM) of the University of Saskatchewan. trapezius, cervical part thoracic part omotransversarius latissimus dorsi sternocephalicus triceps brachii, long head, lateral head brachiocephalicus superficial pectoral deltoideus deep fascia Palpable superficial muscles: The brachiocephalicus and omotransversarius muscles extend the length of the neck. They lie parallel, beside one another, and are closely united at their apposed borders. Where they pass superficial to the omohyoideus muscle (they cover it and it cannot be seen in the above dissection), they are also very closely joined to it. In the donkey, different from the horse, the omohyoideus becomes much wider where it is deep to the omotransversarius and brachiocephalicus. The brachiocephalicus and omotransversarius have distinct attachments: The brachiocephalicus is the more ventral muscle. From its tendinous intersection, a vestige of the clavicle in front of the shoulder, the cleidomastoid part of this muscle passes to the mastoid process of the temporal bone of the skull; and a thin aponeurosis, a cleidooccipital part, passes from its dorsal border to the nuchal crest. The cleidobrachialis part passes from the clavicular intersection to attach distally to the deltoid tuberosity and crest of the humerus. Different from the brachiocephalicus, the omotransversarius arises not from the skull but from the margin of the wing of the atlas and the transverse processes of the following two or three vertebrae. It is quite narrow at its atlantal attachment, and lies beside the dorsal border of the brachiocephalicus the length of the neck. It expands as it extends caudally, becoming much wider. It separates from the cleidobrachialis part at that muscle’s attachment to the humeral crest and continues caudally, attaching to the deep fascia of the lateral shoulder. These relations are shown in the following figures: Fig. 4. The omotransversarius, is narrow at its origin from the wing of the atlas, closely attached to the dorsal border of the brachiocephalicus the length of the neck, and expands caudally at its attachment to the lateral fascia of the shoulder. Brachiocephalicus, its cleidomastoideus part and a thin cleidooccipitalis aponeurosis (not clearly shown here) attach to the mastoid process and nuchal crest; its cleidobrachialis part attaches to the humeral crest. Yellow arrow indicates the caudal, thick, part of the m. cutaneus colli; see discussion below. The original figure, above, by Hermann Dittrich, is in Handbuch der Vergleichenden Anatomie der Haustiere, W. Ellenberger and H. Baum; rev. O. Zietzschmann, E. Ackerknecht, and H. Grau, 1943, Springer Verlag, Berlin. It is redrawn here, and modified slightly, in this drawing by David Stewart Geary. Fig. 5. The insertion of the brachiocephalicus and omotransversarius muscles at the shoulder and arm is shown in the drawing below, which is also by David Stewart Geary: m. cutaneous colli cut away in part here where, as a thin slip, it covers the external jugular vein and, as a thicker bundle (cut away and not shown here, but indicated by a yellow arrow in the figure above), covers the lowest part of the supf. cerv. lnn. external jugular vein superficial cervical lymph nodes m. subclavius m. omotransversarius m. brachiocephalicus Fig. 6. The cutaneous muscles: m. cutaneus faciei m. cutaneus colli, thin part thick part m. cutaneus omobrachialis m. cutaneus trunci The cutaneous muscles lie within the superficial fascia, deep to the dermis layer of the skin to which they attach. They move the skin. Three cutaneous muscles are shown in the shoulder region: m. cutaneus colli, m. cutaneus omobrachialis, and m. cutaneus trunci. The cutaneus colli has a thick part and a thin part. The thick part is a more narrow band, at the angle of junction of the neck and shoulder. It is usually visible under the skin and is palpable. This part arises from the manubrium of the sternum, passing dorsolaterally across the lower jugular furrow; it is the muscle that, in bridging the lower part of the jugular furrow, brings about a small depression in front of its cranial border, the jugular fossa. The thin part continues cranially from the thick part. It passes forward, covering the jugular furrow, and at the angle of the jaw is continuous with the m. cutaneus faciei. This part of the cutaneus colli muscle is very thin. It lies upon the sternomandibularis ventrally, its essentially transverse fibers extending from the ventral neck dorsally and covering the jugular furrow. This is the muscle that, in more excitable animals, contracts and erases the jugular furrow on approach of the veterinarian (and a few other circumstances)! Fig. 7. The figure below shows only the thin part of the m. cutaneus colli; its fibers, which would otherwise conceal the jugular furrow, have been removed to expose the vein. The white dots are placed to show its normal dorsal extent. The location of the thick part of the cutaneus colli is shown by the solid black lines. external jugular vein in the jugular furrow Thin part of the cutaneus colli; it lies upon the sternomandibularis ventrally and is cut away where it would conceal the ext. jugular vein. position of jugular fossa sternomandibularis arising from manubrium Position of thick part of cutaneus colli; it covers the cephalic vein where it joins the ext. jugular and the lower end of the superficial cervical lymph nodes. Fig. 8. In this figure, which is from Ellenberger-Baum, all of the cutaneous muscle of the neck and the trapezius, omotransversarius, brachiocephalicus, deltoideus, and latissimus dorsi muscles are removed. The attachments-portion of the splenius muscle, which is to the transverse processes of the cervical vertebrae and the nuchal crest of the skull, is removed to reveal more clearly the deeper lying muscles. The omohyoideus is distinguished in that it is closely attached to the omotransversarius and brachiocephalicus muscles where they pass superficial to it. Both the omohyodeus and omotransversarius attach caudally to the deep fascia of the shoulder, the omohyoideus medially, the omotransversarius laterally. The two muscles pass forward on either side of the scapula, the subclavius muscle and the superficial cervical lymph nodes. They come together and fuse in front of the lymph nodes. (Note: A close attachment comes about when there is little loose connective tissue between the muscles. In this case the muscles are sometimes described as being “fused.” When the loose connective tissue is abundant, often laden with fat, the muscles slide easily upon one another.) Functionally, a close attachment probably means that the muscles act together, in this case, to draw the shoulder forward and advance the limb. The hyoid attachment of the omohyoideus is complemented by the strong geniohyoideus muscle, which effectively extends the omohyoid attachment from the basihyoideum to the more substantial lower jaw. blue = sternohyoideus position m.splenius; fleshy part that arises from funicular ligamentum nuchae and from the thoracic spines at the withers to basihyoideum area of fusion area in relation to supf. cerv. lnn. m. subclavius Fig. 9. Looking at the standing horse from the left side, you see an inverted “V” whose apex (black arrow) gives the position of the deltoid tuberosity. The line leading down on the right toward the olecranon in the photograph is the ventral border of the lateral head of triceps (yellow arrow in the photo). This line always passes just above the lateral epicondyle of the humerus and the lateral collateral ligament of the elbow joint. The lateral epicondyle is the proximal attachment of the lateral collateral ligament. A little in front of the ligament, passing at the lower border of the lateral head, is the lateral cutaneous antebrachial nerve of the forearm. The nerve is small, but may be palpable. In any case, its position is clear as the lower border of the lateral head is always distinct. The nerve is distributed to the skin here but seldom needs to be blocked. The line leading down to the left (blue arrow in the photograph) indicates the position of the humeral crest, which is the attachment of the brachiocephalicus and the descending superficial pectoral. To the right of the crest, in the interval between the crest and the prominence of the extensor carpi radialis muscle, the skin overlies the brachialis muscle, which is separated from the skin by superficial fascia and a thick layer of deep fascia (deep and superficial fasciae are discussed briefly below). lateral collateral ligament, elbow joint Fig. 10. Cutaneous nerves of the thoracic limb, lateral view at the shoulder. brachialis extensor carpi radialis A brief discussion of the skin and fasciae: The skin is made up of a superficial layer of epithelium, the epidermis, and a deeper layer of dense irregular collagenous connective tissue, the dermis. The epidermis is a stratified squamous epithelium; it forms a fairly uniform, thin, layer except on surfaces subject to considerable wear: the pads of the feet, hoof and claw, lips and muzzle. In these places in our domestic animals it can be several millimeters thick. Thin or thick, it is often pigmented. The epidermis lacks vessels and nerves. Except on areas of the skin subject to wear, the dermis is much thicker than the epidermis, its thickness depending on whether it covers a relatively protected area of the body (medial surface of the limbs, ventral surface of the abdomen) or an area more exposed to the elements. Thus, the dermis layer of the ventral abdomen is thinner as the abdominal skin is a more protected area but there is a gradual increase in dermal thickness upon the sides of the body and it is thickest on the back. Different from the epidermis, the dermis contains small vessels, and sensory and autonomic nerves. These nerves are small and difficult to discern grossly; but this essential difference between the dermis, which is innervated, and the epidermis, which is not, is the basis for techniques of horse-shoeing, nail trimming in small animals, and the like. Epidermis and dermis constitute the skin or cutis. Beneath the dermis is the subcutis or subcutaneous tissue; it is what we designate superficial fascia and the terms may be used interchangeably. The subcutis is a loose connective tissue. It forms a continuous layer that is uniformly distributed under the skin and joins the skin to underlying tissues. The subcutis is the superficial fascia, which contains collagenous, elastic, and reticular fibers, intercellular substance, and bears varying amounts of fat, which make it possible to slide the skin over the underlying tissues: deep fascia, muscle and bone. The subcutaneous tissue is scant or absent in those places (hoof, muzzle of cattle, for example) that allow little or no sliding of the cutis on the underlying tissues. The large superficial veins and cutaneous nerves that we observe and palpate in the live animal all occupy the layer of superficial fascia. Fig. 11. Reflected skin of the ventral abdomen of a donkey. cutis = skin epidermis, thin epithelial layer, often pigmented; dermis, thicker connective tissue layer, unpigmented subcutis = subcutaneous tissue = superficial fascia = The deep fascia is different from the superficial fascia. It is always present as a welldefined sheet or as two or more sheets of collagenous connective tissue deep to the superficial fascia. Different from the superficial fascia, which is a single, uniform, continuous layer beneath the skin, the deep fascia is not a continuous layer beneath the superficial fascia. It is associated with, and in large part brought about by, the action of muscles in which the fascia forms compartments for the individual muscles and, with particular muscles, may form part or all of the muscle’s tendon/aponeurosis of action and attachment. In places as, for example, on the thigh and leg, the tension created by the action of several muscles results in the deep fascia’s being in several layers. In this case, there will be sufficient loose connective tissue between the layers to permit the sliding of the fascial sheets upon one another. For example, the tensor fasciae latae muscle and biceps femoris muscle insert in common on that part of the fascia lata (the deep fascia of the thigh) that attaches to the patella, patellar ligament(s), the tibial tuberosity and cranial margin of the tibia. This same deep fascia passes superficial to the deep fascia that forms compartments for the muscles of the leg and inserts on the tuber calcanei and other bony prominences at the tarsus. The deep fascia, and the fibers of the dermis, are not well developed at birth. Responding to the different tensions of movement and muscle contraction, they become stronger throughout life and, in the case of the deep fasciae, appear as a sheath around many muscles, particularly those of the limbs. When a muscle, which is basically a fluid suspension, shortens, its volume remains unchanged and the result is an increase in the girth of the muscle. It is this fact that, in the live animal, lets us observe the muscle acting in different phases of movement. This swelling of the muscle during contraction also puts tension on the surrounding connective tissue, which is gradually transformed from birth into a well-defined sheath around the muscle. These sheaths have the additional result that, in confining the space in which contraction and swelling take place, pressure is put on neighboring deep veins and arteries. Here the result of muscular contraction is chiefly on the thin-walled veins, which convey the blood at low pressure. The valves in the veins assure that the blood is directed heartward. With exercise and other muscular activity, the venous return to the heart is substantially increased and the heart responds by an increased rate and volume. The large veins in the superficial fascia are also affected this way, the contraction of neighboring muscles pressing them against the more moderate resistance of the skin and superficial fascia. Where bones are just beneath the skin, the superficial and deep fascia fuse with the periosteum. Fig. 12. Of the cross-sections of the forearm below, the figure on the right is taken from Sisson without change. The left figure is the same, modified slightly to emphasize with a yellow-green color the position of the superficial fascia. In the section, the deep fascia and the periosteum with which it fuses are deep to the superficial fascia. (haired) epidermis dermis periosteum superficial fascia deep fascia Fig. 13. A front view of the shoulder appears as shown in the photo below (this is one picture that is covered by copyright. You can probably use it for classroom and personal use, but not for publication or resale without contacting Dreamstime. com): The musculoskeletal and superficial venous anatomy of the shoulder, arm, and forearm are shown in the following 3 figures: the two biceps tendons of insertion: one on the radial tuberosity, one as the lacertus fibrosus joins the extensor carpi radialis tendon. tendon.d Fig. 14. This first figure is a deep dissection. Note that the biceps brachii arises from the supraglenoid tubercle and inserts distally on the radial tuberosity, which is medial on the proximal forearm. The biceps passes medial to the humeral crest. The tendons of the cleidobrachialis and descending superficial pectoral insert at the crest, which is palpable. The brachialis lies in the brachial groove (sulcus) lateral to the humeral crest. Distally, it inserts with the biceps on the proximal medial forearm. The supraspinatus splits above the supraglenoid tubercle to insert on the humerus at the cranial part of the greater and lesser tubercles. position of the thick part of the m. cutaneus colli m. omotransversarius m. brachialis m. cleidobrachialis m. pectoralis supf. descendens m. pectoralis supf. transversus m. ext. carpi radialis m. ext. digitalis com. Fig. 15. Fig. 16. Drawn by David Stewart Geary at the University of Saskatchewan m. cutaneus colli, thin part (cut away where it covers the ext.jugular vein) m. sternocephalicus m. pectoralis supf., pars descendens m. pectoralis supf., pars transversus m. omotransversarius m. brachiocephalicus, pars cleidobrachialis Fig. 17 Fig. 18 The left photograph, which is of an American Quarterhorse, is taken from Horse Illustrated, August 2012 issue; Bob Langrish is the photographer. The right figure is drawn by David Stewart Geary after a figure originally prepared by Hermann Dittrich and the anatomists W. Ellenberger and Hermann Baum. The thin part of the m. cutaneus colli is not shown in either drawing. Fig. 19 Fig. 20 The tendon of origin of the biceps is palpable, fibrocartilaginous where it passes over the intertubercular groove, and bears a deep sulcus that accommodates the intermediate tubercle. It is underlain here by a large bursa. The belly of the muscle is deep to the cleidobrachialis and palpable. It rests on the cranial surface of the humerus and the humeral attachment of the coracobrachialis. Inject the bursa by passing the needle upward, deep to the muscle belly. The bicipital bursa of the horse is large. It is separate from the shoulder joint capsule in this species and must be injected separately. (In the dog, it is an extension of the joint capsule so that injection of either reaches both.) Figure 21, below, shows the biceps tendon lifted off the cartilage covered cranial lip of the proximal end of the right humerus. The picture on the right is taken from The equine bicipital apparatus - review of anatomy, function, diagnostic investigative techniques and clinical condition, A. M. MCDIARMID; Equine Vet. Educ. (1999)11 (2) 63-68. It has been rotated; the original figure is of the left humerus. The photograph of the humerus is from Sisson. fibrocartilage of biceps tendon with deep sulcus accommodating the cranial lip intermediate tubercle greater tubercle lesser tubercle intermediate tubercle The synovial membrane with the cartilaginous bursal surfaces of the biceps tendon and of the cranial lip of the proximal end of the humerus enclose a space that normally is small and the synovial fluid is scant. With inflammation, bursitis, the synovia (synovial fluid) is increased. The bursal membrane stretches and outpouches distally. Blocking of the cutaneous nerves (shown in lateral view in Fig. 22), some of which are not palpable, may be accomplished by following the border of the muscle from which they emerge. The lateral cutaneous antebrachial nerve, a branch of the radial, emerges always in relation to the ventral border of the lateral head of triceps, cranial to the lateral collateral ligament of the elbow joint. The cranial cutaneous antebrachial nerve, a branch of the axillary, emerges behind the caudal border of the deltoideus. The caudal cutaneous antebrachial nerve, the only branch of the ulnar nerve in the arm, is large enough to palpate. In the horse, the transverse part of the superficial pectoral is scalloped where it attaches to the medial forearm fascia. The caudal cutaneous nerve of the antebrachium always emerges beneath the distal border of the muscle at the indentation of the scallop. This nerve has a large distribution on the caudal forearm and it may be helpful to block this nerve if the skin is to be sutured. The medial cutaneous antebrachial nerve, a branch of the musculocutaneous nerve, emerges between the distal parts of the biceps and brachialis deep to the superficial pectoral. It is large and readily palpable in the proximal medial forearm where it lies in relation to the cephalic vein. The nerve crosses the superficial aspect of the lacertus fibrosus tendon, which in the weight-bearing limb is firm and easily recognized on the craniomedial side of the upper (proximal) part of the extensor carpi radialis belly. The nerve can be identified and palpated here as well. lat. collateral ligament Fig. 22 Fig. 23, below, is from Handbuch der Vergleichenden Anatomie der Haustiere by Wilhelm Ellenberger and Hermann Baum; revised 1943, by Otto Zietzschmann, Ernst Ackerknecht, and Hugo Grau; Springer Verlag. The figure is cropped and modified to emphasize the scalloped appearance of the transverse superficial pectoral muscle at its attachment to the medial forearm fascia of the thoracic limb and the emergence of the caudal cutaneous antebrachial nerve at the indentation of the scallop (in this figure, the nerve has been added only for the left limb). This scalloped attachment of the transverse superficial pectoral does not appear in the donkeys that I have examined; but the nerve is palpable in both of these Equidae. Figure 24. The medial cutaneous antebrachial nerve is seen in this figure, which is from Reinhold Schmaltz’ Atlas der Anatomie des Pferdes (published by Richard Schoetz,1900). common trunk of musculocutaneous and median nerves m. biceps brachiilacertus fibrosus brachiibrachi m. brachialis, tendon musculocutaneous nerve cephalic vein medial cutaneous antebrachial nerve m. extensor carpi radialis In the distal arm, the musculocutaneous nerve departs from its common trunk with the median nerve. It gives off a muscular branch to the brachialis and sometimes to the lower biceps brachii (the muscular branch is concealed by the biceps in this figure) and, as the medial cutaneous antebrachial nerve, extends distally and forward lateral to the biceps brachii. The nerve emerges distally between the biceps and brachialis, deep to the superficial pectoral (removed in this dissection). The nerve passes always superficial to the lacertus fibrosus and can be palpated here upon the strong lacertus tendon. The nerve is large and supplies the skin of the medial limb distally to the level of the fetlock joint. The strong tendon of the superficial, main, part of the infraspinatus can be seen and palpated as it passes over the caudal part of the greater tubercle of the humerus. This surface of the greater tubercle is cartilaginous and forms a part of the wall of the infraspinatus bursa where the tendon rides upon it. cartilage-covered caudal part of greater tubercle supraspinatus attaches here intermediate tubercle Fig. 25, from Sisson. Modified only to show the cartilage covered part of the greater tubercle. point of the shoulder, cranial part of greater tubercle main part of infraspinatus muscle attaches here Fig. 26 Figs. 26 Fig. 27 and 27. The “bump” at the end of the arrow is the infraspinatus tendon as it rides over the cartilage-covered surface of the caudal part of the greater tubercle. The photo used here, Fig. 27, is a cropped part of the picture below, which is from www.freebigpicture.com. The picture is rotated from this original to correspond to the left lateral view of the drawing. The drawing, Fig. 26, is by David Stewart Geary, Medical Illustrator at the Western College of Veterinary Medicine, University of Saskatchewan. Fig. 28