Part 188

The =spermatic arteries= resemble those of the horse.

The =utero-ovarian arteries= are small.

The five pairs of =lumbar arteries= derived from the aorta are distributed much as in the horse. The sixth usually comes from the internal iliac artery.

FIG. 475.—PELVIC ARTERIES OF COW.

Part of the right wall of the uterus and vagina is removed and the cervix uteri is shown in sagittal section. a, Aorta; b, utero-ovarian artery; b′, ovarian, and b″, uterine branch of b; c, external iliac artery; d, right internal iliac artery; e, common trunk of umbilical artery (e′) and middle uterine artery (f); g, ilio-lumbar artery; h, anterior gluteal arteries; i, middle hæmorrhoidal artery; k, posterior uterine artery; l, perineal artery; m, posterior gluteal artery; n, obturator arteries; o, artery of clitoris; p, posterior mesenteric artery; r, anterior hæmorrhoidal artery; s, middle sacral artery; 1, ovary; 2, apparent body of uterus, really apposed horns; 2′, cornu; 3, vagina; 4, cervix uteri; 4′, vaginal part of uterus (os uteri); 5, 5′, broad ligaments, large part of right one removed; 6, urinary bladder; 7, rectum; 8, sacrum; 9, symphysis pelvis. (After Zieger.) ]

The =middle sacral artery= is a vessel about 5 mm. in diameter which continues the aorta. It arises from the dorsal face of the aorta at the angle of divergence of the internal iliacs, runs backward on the pelvic surface of the sacrum a little to the left of the median line, and is continued as the middle coccygeal artery. It gives off small collateral branches to the spinal cord and the muscles of the tail and the =lateral coccygeal arteries=. The latter may have a common trunk of origin, and each divides into dorsal and ventral branches. The =middle coccygeal artery= runs through the ventral (hæmal) arches of the coccygeal vertebræ. The coccygeal arteries are connected at pretty regular intervals by segmental anastomoses.

The =internal iliac arteries= are much longer than in the horse. Each passes backward on the sacro-sciatic ligament and divides about the middle of the pelvic wall into posterior gluteal and internal pudic branches. The chief differences in its distribution are: (1) A large trunk gives origin to the umbilical and middle uterine arteries. The =umbilical artery= is usually largely obliterated and its terminal branches receive their blood through anastomoses with the internal pudic. It gives off near its origin two small vessels, the ureteral artery (A. ureterica) and the deferential artery (A. deferentialis), which accompany the ureter and the vas deferens respectively. The =middle uterine artery= (A. uterina media) is very large. It is distributed chiefly to the cornu of the uterus, and compensates for the small size of the utero-ovarian artery. (2) The =ilio-lumbar= artery is relatively small and is distributed chiefly to the sublumbar muscles. It is sometimes replaced by branches of the circumflex iliac and gluteal arteries. (3) The =anterior gluteal artery= is commonly represented by several vessels. (4) The =obturator artery= is represented by several small branches which supply the obturator and adductor muscles. (5) The =iliaco-femoral= and =lateral sacral arteries= are absent. The absence of the latter is compensated by the middle sacral and gluteal arteries. (6) The =posterior gluteal= (or ischiatic) artery is large. It emerges through the lesser sciatic notch and ramifies in the biceps femoris and adjacent muscles. (7) The =internal pudic artery= (A. urethro-genitalis) is the direct continuation of the internal iliac. It gives off branches to the rectum, bladder, urethra, and genital organs. In the male it supplies the accessory genital glands and divides into dorsal and deep arteries of the penis; the a. dorsalis penis runs along the dorsum penis to the glans and gives twigs to the prepuce; the a. profunda penis gives off a perineal branch and enters the corpus cavernosum penis. In the female it gives off a large posterior uterine artery, which supplies the posterior part of the uterus and gives branches to the vagina and bladder. It ends as the a. clitoridis, which supplies the clitoris and adjacent parts.

ARTERIES OF THE PELVIC LIMB

The =external iliac artery= has the same course as in the horse. The circumflex iliac artery is large. A branch from it emerges between the abdominal and lumbar muscles near the external angle of the ilium and ramifies like the terminals of the ilio-lumbar artery of the horse.

The =femoral= and =popliteal arteries= pursue a similar course to those of the horse. The chief differences in their branches are as follows:

1. The =external pudic artery= is distributed chiefly to the scrotum in the male. In the cow it is usually termed the =mammary= and is very large, especially during lactation. Each divides at the base of the mammary gland into two branches which are distributed to the anterior and posterior parts (“quarters”) of the gland. A small branch accompanies the subcutaneous abdominal vein to the xiphoid region.

2. The =deep femoral artery= gives off an obturator branch which passes up through the obturator foramen to supply the obturator internus and compensates otherwise for the absence of the obturator artery.

3. The =anterior femoral artery= is large. It often gives off the =external circumflex artery= of the thigh, which perforates the proximal end of the quadriceps, gives branches to that muscle, the iliacus, glutei, and tensor fasciæ latæ.

4. The =saphenous artery= is large. It descends in front of the homonymous vein to the postero-internal surface of the hock, where it divides into two plantar branches. The =internal plantar artery= (A. plantaris medialis) is the direct continuation of the saphenous. It descends at first along the inner border of the superficial flexor tendon and is continued as the =internal superficial plantar metatarsal artery= along the inner side of the deep flexor tendon with the internal plantar nerve. It anastomoses at the proximal end of the metatarsus with the perforating metatarsal artery, assisting in the formation of the proximal plantar arch. Near the fetlock it concurs with the perforating branch of the dorsal metatarsal artery in the formation of the distal plantar arch. Below this it is continued as the =internal digital artery=. The =external plantar artery= (A. plantaris lateralis) is small. It descends along the outer border of the deep flexor tendon with the external plantar nerve, concurs with the perforating tarsal and the internal plantar arteries in the formation of the proximal plantar arch, and gives branches to the rete tarsi dorsale. Continuing downward along the deep flexor tendon as the =external superficial plantar metatarsal artery=, it assists in forming the distal plantar arch and becomes the =external digital artery=.

FIG. 476.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF OX, ANTERIOR VIEW.

a, Anterior tibial artery; b, proximal perforating metatarsal artery; c, dorsal metatarsal artery; d, dorsal common digital artery; e, e′, dorsal proper digital arteries. ]

FIG. 477.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF OX, POSTERIOR VIEW.

e, Saphenous artery; f, f′, internal and external plantar arteries; g, g′, internal and external superficial plantar metatarsal arteries; h, deep plantar metatarsal artery; i, j, internal and external plantar digital arteries; k, plantar common digital artery; l, l′, internal and external plantar digital arteries. ]

The =posterior tibial artery= is relatively small and is distributed chiefly to the muscles on the posterior surface of the tibia. Lower down it is replaced by the saphenous artery as described above.

The =anterior tibial artery= has the same course as in the horse. It is continued down the groove on the front of the metatarsal bone as the =dorsal metatarsal artery=. This is the chief artery of the region and is accompanied by two veins. It detaches the proximal perforating metatarsal artery, which passes through the proximal foramen of the metatarsal bone and concurs with the superficial plantar arteries in forming the proximal plantar arch. Near the distal end of the metatarsal bone it gives off the distal perforating metatarsal artery which passes back through the distal metatarsal foramen and assists in forming the distal plantar arch. The two arches are connected by the small =deep plantar metatarsal artery= which lies in the groove on the posterior face of the large metatarsal bone.

The =dorsal common digital artery= is the direct continuation of the dorsal metatarsal. It divides into two branches which unite in the interdigital space with the corresponding branches of the plantar common digital to form the proper digital arteries.

The =plantar common digital artery= descends from the distal plantar arch, anastomoses in the interdigital space with the internal and external digitals, and divides into two branches which join those of the dorsal common digital artery as before mentioned.

The foregoing is a brief statement of the more common arrangement of the vessels in the distal part of the limb, but minor variations are very common.

THE VEINS

The =vena hemiazygos= usually takes the place of the vena azygos. It lies along the left side of the aorta and the bodies of the thoracic vertebræ, turns down across the left face of the aorta and left pulmonary artery, runs back over the left auricle and opens into the great coronary vein or the right atrium. It receives the intercostal veins.

Two =jugular veins= occur on either side. The =internal jugular vein= (V. jugularis interna) is a relatively small vessel which accompanies the carotid artery. It arises by occipital, laryngeal, and thyroid radicles, receives tracheal, œsophageal, and muscular branches, and joins the external jugular near its termination. It is sometimes absent, but in some cases it appears, on the other hand, to be large enough to interfere with venesection practised on the external jugular. The =external jugular vein= (V. jugularis externa) is very large and corresponds to the single jugular of the horse. It is separated from the carotid artery in the greater part of its course by the sterno-cephalicus and omo-hyoideus muscles.

The =inferior cerebral vein= usually does not unite with the occipital; the latter is continued by the internal jugular vein.

The =orbital veins= form a network between the periorbita and the muscles of the eyeball. This plexus communicates with the cavernous sinus and with the superior cerebral vein. It is also drained by the =frontal vein= which runs in the supraorbital canal and groove and joins the angular vein of the eye.