UTERINE BLOOD FLOW 



1587 



fig. 2. Arrangements of arte- 

 rial and venous pathways to 

 uterus simplex (left) and uterus 

 duplex (right). The "circle" of 

 the arterial pathway is shown as a 

 continuous pathway from the 

 aorta, ovarian artery, uterine 

 artery, hypogastric artery (uterus 

 simplex), femoral artery, and 

 aorta. A similar circle exists in 

 the venous connections. [After 

 Byron Robinson (211).] 



of the uterus, the arteries anastomose with a branch of 

 the ovarian artery, one on each side. The uterine 

 arteries supply, therefore, part of the vagina, the 

 uterus, and fallopian tubes on each side. 



Since the ovarian arteries arise from the aorta just 

 below the renal arteries, it will be seen that there is, 

 indeed, a large communicating arterial circle supply- 

 ing the uterus on each side of the midline. In the case 

 of partial or complete uterine fusion during develop- 

 ment there is further connection of the finer arterial 

 branches from both sides in the body of the uterus 

 [Faulkner (77, 78)]. The arcuate arteries of the uterus 

 lie in the zona vascularis in the myometrium. Myomas 

 in the smooth muscle of the uterus are singularly 

 deficient in blood supply (see fig. 3) [Faulkner (77), 

 Holmgren (1 13)]. 



We observe in this arrangement that the uterus 

 simplex is supplied from two primary arterial sources, 

 on each side, and that where the form of the uterus 

 permits, there is free union between these. It is possible 

 to see that the uterus, which increases along with its 

 blood vessels many times over in size during gestation, 

 is assured of a reasonably large and constant head of 

 arterial pressure at all times. 



The morphology of the venous drainage of the 

 uterus is equally important for the physiological 

 changes that take place in the uterus and its circula- 

 tion. The uterine veins, without valves, arise from 

 within the tissues of the uterus and enter the broad 

 ligament at numerous points in increasingly large 



venous channels as smaller ones have united along 

 the way. However, there are four main venous paths 

 of exit from the uterus [Bieniarz (31)]. In the common 

 laboratory animals, the veins of the broad ligaments 

 unite and form rather uncomplicated plexuses in the 

 broad ligament [Reynolds ( 1 98)] receiving veins from 

 the uterus along the way. The parametrial veins join 

 with ovarian veins to drain blood toward their point of 

 entrance into the inferior vena cava on the right side 

 and the renal vein on the left side. 



As with many parts of the venous system, the 

 drainage connections are complex, rather than dia- 

 grammatically simple as is commonly believed. In 

 the primate, these relations are more complicated 

 than in the usual laboratory animals. For example, in 

 the broad ligament of primates, there is an extensive 

 pampiniform plexus, having multiple connections 

 with the pudendal veins, the several rectal plexuses, 

 the internal iliac veins, and inferior vena cava. Not 

 only may uterine blood move toward the heart 

 through the inferior vena cava, but through the 

 internal and superficial epigastric veins to the mam- 

 mary and internal costal veins as well. Blood may 

 also, if pressure within or upon the venous system 

 requires it, flow to the ascending lumbar veins, by 

 way of segmental connections, to the azygous and 

 hemiazygous veins. 



The ovarian vein enlarges greatly during pregnancy 

 [Borell & Fernstrom (38), Hodgkinson (no)]. There 

 is much current interest in this subject, first stressed 



