i 5 86 



HANDBOOK OF PHYSIOLOGY ^ CIRCULATION II 



tubes, and a cervix. These several types of uteri are 

 recognized as the uterus duplex, the uterus bicornis, 

 and uterus simplex; the latter representing, para- 

 doxically, the most complicated organization of all, 

 being, as it is, the fusion of paired simple ducts into a 

 single complex organ. Just as increasing degrees of 

 complexitv of organization may be seen throughout 

 the phyla so, in the development of the uterus simplex, 

 all the transitional stages of development from the 

 duplex to the simplex form are recognized. Persistence 

 of incompletely formed uteri as malformations 

 sometimes complicates the parturitional process. No 

 one has produced experimentally arrested fusion or 

 partial development of the uterus simplex, probably 

 for the simple reason that no studies of experimental 

 teratogenesis have been made in primates. 



Since the several classes of uteri have in common an 

 orderly and progressively more complex organiza- 

 tion, one might anticipate that there would be an 



FIG. I. Comparative types of uteri from the uterus duplex to 

 the uterus simplex found in various mammals: .-1, monotreme 

 [Echidna aculeala); B, marsupial (Didelphis virginiana); C, rodent 

 (rabbit); D, carnivore (dog); E, ungulate (mare); /•', primate 

 (Macacus rhesus). [After Rudolph and Ivy, taken from Reynolds 

 (198)-] 



orderly and progressively more complex organization 

 of the vasculature of the uterus among different 

 animals. So there is. 



ANGIOGENESIS IN THE LTERUS 



All organogeny takes place around a primary 

 \ ascular organizational pattern [Evans (71)]. Blood 

 vessels begin as a diffuse capillary network, some 

 channels of which become more and more prominent, 

 larger and structurally more complex as arterial and 

 venous pathways come into being [Thoma (233)]. 



Why this is so is not clear, although Thoma has 

 postulated that the process is governed in part by the 

 hemodynamic load imposed upon certain parts of the 

 delicate capillary system. As these pathways become 

 more defined, they give rise to still further differ- 

 entiation of more peripheral branches. The sizes and 

 angles of these branches are related to certain physical 

 relationships that were first laid down by Hess (105) 

 on thermodynamic grounds, and first given substance 

 experimentally by Reynolds (197) in the developed 

 vascular tree. However, more than simple hemody- 

 namics is involved, since Price (177) has shown that 

 organogenesis can take place in tissue culture only if 

 a semisolid medium is used, but not if a liquid medium 

 is employed. Thus the dependence or role of vascular 

 development as a contributory mechanism to or- 

 ganogenesis is seen to be unessential for primary 

 organization, but to be essential for subsequent devel- 

 opment. 



VASCULAR CONNECTIONS OF THE UTERUS 



The common vascular denominator for all uteri is 

 the pattern of vascular supply of blood to, and drain- 

 age of blood from, the uterus. This was certainly seen 

 by Aristotle, by Vesalius, and by Hunter. It was not 

 stressed as a vascular complex, apparently, until the 

 early part of this century by Byron Robinson (211). 

 This author compared in different species the vascular 

 circle that starts in the aorta by way of the anterior 

 division of the internal iliac arteries on each side, or 

 may arise in common with the vaginal, umbilical, or 

 middle rectal arteries. The uterine arteries descend 

 in the fat at the base of the broad ligament and, going 

 between the layers of that ligament, pass to the uterus, 

 following a tortuous course. They run along the 

 mesial sides of the uterus, giving off branches to the 

 bodv of the uterus along the way. At the cephalic end 



