STUDIES ON THE VASCULAR SUPPLY OF THE UTERUS OF A COW : II. MORPHOLOGICAL INVESTIGATION OF ARTERIES ON THE UTERINE WALL WITH SPECIAL REFERENCE TO THOSE IN THE CARUNCULAR REGION

The arterial system of the bovine uterus has been studied by Ellenbogen, Hanseland Asdell, Hilliger, Reuber and Emmerson, and Tsutsumi. Nevertheless, there havebeen only a few accounts on comparative studies regarding the caruncular region ofnulliparous heifer, multiparous cow, and pregnant cow. In the present investigation, atotal of 61 uteri from l 1 nulliparous heifers, 12 multiparous cows, and 38 pregnant cowswere used. Casts of arteries were prepared for this purpose by means of the intra-vascular injection of acrylic resin. Apart from the casts just mentioned above, tissueblocks were obtained from some uteri injected with resin. Transparent slices andcelloidin sections were also made. In addition to resin-injected materials, those injectedwith gelatine were also used. Paraffin sections of the caruncle were prepared fromnon-injected materials fixed in 10% formalin, Carnoys, Zenkers, or Bouins fluid, andstained with hematoxylin and eosin.The arcuate artery proceeded toward the antimesometrial margin within the stratumvasculare of the uterine wall. Many of them anastomosed with adjacent ones in arxarchfasluion at about 1/2 to 2/3 of the circumference of the horn from the mesometrialmargin. Finally, they terminated in an anastomosis with those of the contralateral rowon the antimesometrial margin. Meanwhile, many smaller arcuate arteries joined thearchfashioned anastomoses described just above. The arcuate arteries in a nulliparousheifer were nearly straight until they formed an anastomosing net, and thereafter theybecame strongly tortuous. On the other hand, those in multiparous cows were stronglytortuous throughout their course. Meanwhile, those arteries were almost straight ina cow which was in the second half of pregnancy.The arcuate artery gave ofl a radial artery to the caruncle and a branch to thecircular muscle. The radial artery usually give origin to a basal artery within thestratum vasculare, which supplied inner one-third of the circular muscle and stratum basale of the endometrium. The main trunk of the radial artery usually bifurcatedonce or twice in the endometrium and finally divided into many arterioles at the baseof the caruncle. These arterioles gave off many pre-capillary vessels which, in turn, continued to the subepithelial capillary net. TIIC radial arteries, especially those inthe caruncular region, were much more tortuous in the multiparous cow than in thenulliparous lueifer. Well-developed capillary networks were also present in the circularmuscle.In tlne second half of pregnancy, the arteries became adapted to the expansion ofthe uterus witlt the following modifications. The radial artery proceeded toward thetop of the peduncle, taking a course almost perpendicular to the base of it. Then, it divided into many arterioles, which proceeded to the bottom of the placentome, takinga fan-fashioned course. At the base of the placentome, these arterioles gave origin tocaruncular radial arteries, which were found to be rather thin at tlaeir origin and whichbecame thicker on their way to the surface of the placentome. The caruncular radialarteries in t[te placentome seemed to be an extension of the pre-capillary vessels whichwere invariably found near the surface of a caruncle in the nulliparous heifer, as wellas in the mu[tiparous cow.