Part 192

The =posterior mesenteric artery= arises near the termination of the aorta. It is small and is distributed like that of the ox.

Six pairs of =lumbar arteries= arise from the aorta. The seventh comes from the middle sacral.

The terminal branches of the aorta resemble those of the ox.

The arteries of the shoulder, arm, and forearm resemble in general those of the ox.

FIG. 482.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF PIG, ANTERIOR VIEW.

a, Anterior tibial artery, continued on tarsus as the dorsalis pedis; b, perforating tarsal artery; c, dorsal metatarsal arteries; d, common digital arteries; e, proper digital arteries. ]

FIG. 483.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF PIG, POSTERIOR VIEW.

f, Saphenous artery, continued as internal tarsal artery; g, external tarsal artery; h, internal plantar artery; h′, external plantar artery; i, perforating tarsal artery; j, deep plantar metatarsal arteries; k, common digital artery; l, proper digital arteries. ]

The main facts as to the =metacarpal= and =digital arteries= are as follows: The rete carpi dorsale is formed essentially by the terminals of the interosseous artery of the forearm. It gives rise to three =dorsal metacarpal arteries= which descend in the corresponding interosseous spaces and unite with branches of the volar metacarpals to form three =common digital arteries=. Each of these divides into two =proper digital arteries=, which descend along the interdigital surfaces of the digits. On the volar surface are two =volar arches=, superficial and deep, from which three =superficial= and three =deep volar metacarpal arteries= arise. The deep arteries unite near the distal end of the space between the principal metacarpal bones to form a stem which unites with the middle (third) superficial artery. The superficial arteries unite to form an arch from which =proper digital arteries= are given off to the axial aspect of the small digits, and a common digital which supplies two =volar proper digital arteries= to each of the chief digits.

The arteries of the hip, thigh, and leg are arranged much as in the ox. A few special features may be noted.

The =ilio-lumbar artery= gives off a branch to the quadriceps femoris. It may also supply the posterior abdominal artery, which otherwise arises from the deep femoral.

The =deep femoral artery= is given off above the level of the pubis. The posterior abdominal and external pudic arteries may arise from it by a short common trunk or separately. The =external pudic= gives branches to the prepuce but not to the penis. The =popliteal artery= gives off the peroneal.

The =femoral artery= gives off a short trunk which divides into anterior femoral and external circumflex arteries, the latter being much the larger.

The =saphenous artery= is large. It descends on the inner surface of the leg and hock and concurs with the perforating tarsal artery in forming the proximal plantar arch.

The =posterior tibial artery= is small, being replaced distally by the saphenous. It gives branches to the muscles on the posterior face of the tibia and supplies the nutrient artery of that bone.

The =anterior tibial artery= is continued as the dorsalis pedis on the flexion surface of the tarsus. This gives off the =perforating tarsal artery=, which passes back through the vascular canal of the tarsus and unites with the terminal branches of the saphenous to form the proximal plantar arch.

The =metatarsal= and =digital arteries= resemble in arrangement the corresponding vessels of the fore limb.

THE VEINS

The veins resemble in general those of the ox. Thus there is a hemiazygos vein and two jugular veins, the internal one being relatively larger than in the ox. A few differential features may be noted.

The =buccinator vein= resembles that of the horse, and unites with the =vena reflexa= to form a short common trunk which joins the facial.

The =facial vein= resembles in general that of the horse. The =dorsal nasal vein= is large, receives the veins from the snout, runs backward in the groove of the nasal bone and joins the frontal vein; it is connected with its fellow by a transverse branch, and anastomoses freely with the malar and facial.

The veins of the distal parts of the limbs naturally present differences which are correlated with those of the arteries.

THE LYMPH VESSELS AND GLANDS

The =thoracic duct= often divides near its termination into two branches which unite to form an ampulla. The latter suddenly contracts and opens into the terminal part of the left jugular vein.

The =submaxillary lymph glands= are situated in the space between the omo-hyoid and internal pterygoid muscles in relation to the lower part of the anterior border of the submaxillary salivary gland. There are commonly two on each side, one large, the other small.

The =parotid lymph glands= (Fig. 309) are reddish-brown in color. There are usually four of considerable size on either side. One is situated at the upper part of the posterior border of the masseter, partly covered by the parotid gland. Another large subparotid gland lies below the base of the ear. Ventral to this are two smaller glands, one above and one below the external jugular vein.

The =pharyngeal= (or retropharyngeal) =lymph glands= (Fig. 310) are situated on the dorsal wall of the pharynx above the external carotid artery and below and behind the paramastoid process. There are usually two of considerable size on either side.

The =middle cervical lymph glands= form a group on the mastoido-humeralis on the course of the external jugular vein.