Part 194

The great coronary vein ascends in the left longitudinal groove to the coronary groove, in which it winds around the posterior face of the heart to the right side and opens into the right atrium below the posterior vena cava. Near its termination it receives one or two veins which ascend along the right longitudinal furrow. Several small veins from the wall of the right ventricle open into the right atrium separately or by a common trunk.

THE ARTERIES

There is no common brachiocephalic trunk (anterior aorta). Two large vessels arise from the convexity of the aortic arch; these are the =brachiocephalic= and =left brachial arteries=. The =brachiocephalic= gives off the two =carotid arteries=, no common trunk being present. It frequently also supplies the posterior thyroid artery. The intrathoracic branches of the brachial arteries are as follows:

A common trunk gives off the =dorsal=, =subcostal=, and =superior cervical arteries=. The dorsal artery passes out in front of the first rib, and the superior cervical through the first intercostal space. The latter is relatively small.

FIG. 485.—ARTERIES OF THORACIC CAVITY AND PART OF NECK OF DOG.

a, Aortic arch; a′, thoracic aorta; b, brachiocephalic artery; c, left brachial artery; d, d, common carotid arteries; e, vertebral artery; f, dorsal artery; g, deep or superior cervical artery (usually given off from a common trunk with f); h, extrathoracic part of f; i, subcostal artery; k, inferior cervical artery; l, descending branch of k; m, ascending branch of k; n, internal scapular; o, acromial; p, superficial cervical; q, s, extrathoracic part of left brachial; r, external thoracic; t, internal thoracic; t′, asternal; t″, anterior abdominal; u, perforating branch of t; v, anterior mediastinal (thymic); w, ventral intercostals; x, bronchial; y, œsophageal; y′, dorsal intercostals; z, descending branch of left coronary artery; z′, circumflex branch of same; 1, œsophagus; 2, trachea; 2′, bronchi; 3, first rib (sawn off); 4, right ventricle; 5, left ventricle; 5′, left auricle; 5″, pulmonary artery (cut off); 6, diaphragm; 7, 8, 9, last three cervical vertebræ; 10, thymus. (After Ellenberger, in Leisering’s Atlas.) ]

The =vertebral artery= may arise either in front of or behind the trunk above mentioned; in the latter case it crosses the inner face of the trunk. It passes along the neck in typical fashion to the third cervical vertebra and divides into three branches. The largest of these supplies the muscles in this region, compensating for the absence of branches of the superior cervical artery. The second passes between the second and third cervical vertebræ into the vertebral canal and unites with the opposite artery and a branch of the occipital artery to form the basilar. The third branch is the small continuation of the parent trunk; it passes to the wing of the atlas and anastomoses with the occipital.

The =inferior cervical artery= gives off the superficial cervical which ascends in front of the supraspinatus.

The =internal thoracic artery= is large and sends perforating branches to the pectoral mammary glands.

The =external thoracic artery= arises outside of the thorax and sends branches to the mammary glands.

The =common carotid arteries=, left and right, arise in that order from the brachiocephalic. In the neck the right one lies on the trachea, the left on the œsophagus. Collateral branches are the posterior thyroid (which may, however, arise from the right or left brachial or the inferior cervical), pharyngeal, thyro-laryngeal muscular, tracheal, and glandular (to the submaxillary gland). Each carotid divides under the wing of the atlas into occipital and internal and external carotid branches.

FIG. 486.—SUPERFICIAL VESSELS OF HEAD OF DOG.

1, Facial artery; 2, inferior labial artery; 3, artery of angle of mouth; 4, superior labial artery; 5, lateral nasal artery; 6, dorsal nasal artery; 7, superficial temporal artery; 8, transverse facial artery; 9, anterior auricular artery; 10, zygomatico-orbital artery; 11, satellite vein of 10; 12, ant. auricular vein; 13, superficial temporal vein; 14, internal maxillary vein; 15, post. auricular vein; 16, 17, external jugular vein; 18, external maxillary vein; 19, 23, facial vein; 20, inf. labial vein; 21, buccinator vein; 22, vena reflexa; 24, superior labial vein; 25, vena angularis oculi; 26, dorsal nasal vein; a, concha; b, parotid gland; c, submaxillary gland; d, submaxillary lymph glands; e, mylo-hyoideus; f, digastricus; g, masseter; h, zygomaticus; i, scutularis; k, temporalis; l, orbicularis oculi; m, zygomatic arch; n, retractor anguli oris; o, buccinator. (Ellenberger-Baum, Anat. d. Hundes.) ]

The =occipital artery= is small. It gives off =condyloid= and =posterior meningeal= branches, passes up through the notch on the anterior margin of the wing of the atlas, and is distributed to the muscles of this region. Its =cerebrospinal= branch passes through the intervertebral foramen, and unites in the vertebral canal with its fellow and a branch from the vertebral artery to form the basilar. A retrograde branch anastomoses with the vertebral as in the horse.

The =internal carotid artery=, also small, passes to the foramen lacerum posterius, enters the carotid canal and forms a bend before entering the cranium through the carotid foramen. It forms a plexus which is connected by branches with the middle meningeal and ophthalmic arteries. It then perforates the dura mater and enters into the formation of the arterial circle (of Willis).

The =external carotid artery= is the direct continuation of the common carotid. It passes along the lateral wall of the pharynx, emerges from beneath the digastricus, and divides into superficial temporal and internal maxillary arteries. It gives off the large flexuous =lingual artery= which has a course similar to that of the horse. The =external maxillary=, smaller than the lingual, passes along the upper border of the digastricus, gives off the sublingual, gains the anterior border of the masseter, and divides into superior and inferior labial and the angularis oris. The last-named vessel passes forward on the cheek between the labials to the angle of the mouth. The =sublingual artery= passes at first along the upper border of the digastricus and continues between the mylo-hyoideus and the ramus of the mandible. The =posterior auricular artery= arises at the anterior border of the digastricus, gives branches to the salivary glands and the adjacent muscles, and ascends on the convex face of the concha. It divides into two branches which return along the borders of the external ear.

The =superficial temporal artery=, after giving off the =anterior auricular artery= and a small =transverse facial artery=, turns forward under the temporal fascia toward the eye, and divides into upper and lower branches which supply the frontal region and the eyelids. It also supplies branches to the parotid gland and the masseter and temporalis muscles.

The =internal maxillary artery= pursues a course similar to that of the horse. The mental branches of the =inferior alveolar= (or dental) =artery= are of considerable size and are distributed in the lower lip and gums. Two or three =deep temporal arteries= are present. The anterior one may arise from the buccinator; it gives off the middle meningeal, which sends a branch to the carotid plexus. The =ophthalmic artery= gives off a branch which enters the cranium through the foramen lacerum orbitale and connects with the internal carotid; this is termed the internal ophthalmic and gives off the arteria centralis retinæ. The superficial branches of the =infraorbital artery= replace the dorsal and lateral nasal arteries, and compensate for the small size of the superior labial.

The =brachial artery= in its course in the arm presents no special features. At the elbow it passes between the biceps and the pronator teres, descends (as the median) under the flexor carpi radialis about a third of the way down the forearm, and divides into radial and ulnar arteries. Among its collateral branches are: (1) The =subscapular artery=, which passes up between the subscapularis and teres major, turns around the posterior angle of the scapula and terminates in the supraspinatus, deltoid, trapezius, and mastoido-humeralis. In about half the cases it gives off the =anterior circumflex=, which often arises with the =posterior circumflex=. Its other branches resemble those of the horse. (2) The =anterior circumflex artery= (in about half the cases). (3) The =deep brachial= arises about a third of the way down the arm. (4) The =bicipital artery= (for the biceps) is given off at the lower part of the arm. (5) The =proximal collateral radial artery= (not present in the horse) arises at the lower fourth of the arm, crosses over the terminal part of the biceps, descends on the extensor carpi radialis, and concurs with a branch of the volar interosseous in forming the rete carpi dorsale. It often supplies the bicipital artery. (6) The =anterior radial artery= (A. collateralis radialis distalis) is very small. (7) The =common interosseous artery= is given off a little below the elbow. It supplies branches to the flexor muscles and the =dorsal interosseous artery=, which passes through the interosseous space, gives branches to the extensor muscles, and by its terminal twigs concurs in the formation of the rete carpi dorsale. The direct continuation of the trunk is the =volar interosseous artery=, which descends under cover of the pronator quadratus, gives off a branch to the rete carpi dorsale and the =fifth volar metacarpal artery=, and terminates by joining the volar branch of the radial artery to form the deep volar arch. (8) The =volar antibrachial artery= (Ramus volaris antibrachii) arises below the interosseous and descends at first under the flexor carpi radialis, then between the heads of the deep flexor, and divides into ascending and descending branches.

The =radial artery=, the smaller terminal of the brachial, descends along the inner border of the radius, and divides near the carpus into dorsal and volar branches. The =dorsal branch= assists in forming the rete carpi dorsale. The larger =volar branch= descends behind the inner border of the carpus and joins the end of the volar interosseous in forming the =deep volar arch=. From this arch three =deep volar metacarpal arteries= descend in the second, third, and fourth intermetacarpal spaces and concur with the corresponding superficial volar and the dorsal arteries to form the common digitals.

FIG. 487.—VESSELS AND NERVES OF INNER SURFACE OF SHOULDER AND ARM OF DOG.

a, b, Brachial artery; c, subscapular vessels; d, thoracico-dorsal vessels; e, deep brachial vessels; f, superior collateral ulnar vessels; g, brachial vein; h, h″, cephalic vein; h′, mediano-radial vein; i, anterior thoracic nerves; k, musculo-cutaneous nerve; l, median nerve; m, ulnar nerve; n, radial nerve; o, thoracico-dorsal nerve; 1, subscapularis muscle; 2, supraspinatus muscle; 3, teres major; 4, latissimus dorsi; 5, deep pectoral muscle; 6, biceps brachii; 7, long head of triceps; 8, tensor fasciæ antibrachii; 9, internal head of triceps; 10, pronator teres. (Ellenberger-Baum, Anat. d. Hundes.) ]

FIG. 488.—ARTERIES OF FOREARM OF DOG, INNER VIEW.

a, Brachial; a′, median; c, common interosseous; d, volar antibrachial; e, radial; e′, e″, dorsal and volar branches of e; f, f′, cutaneous branches of e; g, ulnar; 1, biceps brachii; 2, extensor carpi radialis; 3, pronator teres; 4, deep digital flexor; 5, radius; 6, superficial digital flexor; 7, flexor carpi radialis; 8, flexor carpi medius; 9, humerus. (Ellenberger-Baum, Anat. d. Hundes.) ]

The =ulnar artery= descends on the deep flexor of the digit, and sends a connecting branch to the radial above the carpus. Near the middle of the metacarpus it gives off the =first volar metacarpal artery= and divides into the =second=, =third=, and =fourth superficial volar metacarpal arteries=. The first volar artery unites with the corresponding dorsal artery to form the =first common digital artery=, which supplies proper digital arteries for the opposed surfaces of the first and second digits. The superficial volar arteries descend in the spaces between the other metacarpal bones, unite near the metacarpo-phalangeal joints with the corresponding deep volar and dorsal metacarpal arteries to form three =common digital arteries=. Each of the latter divides after a short course into two =proper digital arteries=, which run along the opposed surfaces of the second to the fifth digits. The external digital artery of the fifth digit comes from the =superficial volar arch= formed by the union of a branch of the volar interosseous with the fourth superficial volar metacarpal artery.

FIG. 489.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF DOG, ANTERIOR VIEW.

a, Branch of volar interosseous artery; b, proximal collateral radial artery (external branch); c, radial artery (dorsal branch); d, rete carpi dorsale; e, deep dorsal metacarpal arteries; f, superficial dorsal metacarpal arteries; g, common digital arteries; h, proper digital arteries. ]

FIG. 490.