1604 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



_RPI _, 



fig. 16. Injected arteries of rabbit uterus on 12th day (/), 

 16th (2), 20th (3, side view; ,/, antimesometrial view), 22nd 

 (5 and 6) 24th (7 and <?) of gestation. Note diminishing in- 

 jectibility of blood vessels as uterus reaches maximum spheroidal 

 distention on day 22. [From Reynolds (199). 



part of a common vascular bed, flow to the other area 

 is favored, since the peripheral vascular resistance 

 there, while unchanged, is relatively less than in the 

 first area. Study of the vascular rearrangements in the 

 pregnant monkey uterus show that a comparable 

 pattern of vascular arrangements occur in the uterus 

 simplex [Gillespie et al. (83), Ramsey (187)]. 



Physiologists have long been concerned with uterine 

 blood flow. Barcroft and his associates measured 

 total uterus blood volumes and blood flows in the 

 uterus of the rabbit throughout pregnancy [Barcroft 

 et al. (20), Barcroft & Rothschild (21)]. It was found 

 that both increase but in dissimilar patterns. From a 

 content of about 2 ml at the outset of pregnancy in the 

 rabbit, the uterine blood volume increases to more 



than 30 ml by day 27, whereupon it declines 50 per 

 cent in the next 3 days. The blood flow increases to 

 two peaks of 30 ml per min on the 20th and 27th 

 days (gestation 31 days), with the decline in total 

 blood flow to less than 20 ml on day 24. It will be 

 seen that the local deprivation of blood in uterine 

 tissues described in the regional studies above were 

 reflected also in the total blood flow' [Reynolds (192)]. 

 Page (167), using an indirect method of reasoning 

 based on facts, shows that in the ninth month of 

 pregnancy in women there is a decline of nearly one- 

 half in uterine blood flow. 



The turnover of blood in the pregnant rabbit uterus 

 based on the flow divided by the volume, shows a 

 progressive increase from about 60 per cent turnover 

 on the 1 2th day of pregnancy to 1 75 per cent turnover 

 on day 20 with a sustained 75 to 85 per cent turnover 

 after uterine conversion. Comparing the turnover 

 characteristics with the factors of uterine growth and 

 distention, one sees how affected by or related to these 

 factors the uterine circulation is [Reynolds (192)]. 



Recent studies have been directed toward the meas- 

 urement of total uterine blood flow in sheep and 

 humans. These have been of three types. In the sheep 

 and humans, arterial and venous blood sampling and 

 application of the Fick principle have been used. In 



days 



fig. 17. A: blood flow (x) and blood volume (•) in rabbit 

 uterus during pregnancy. B: percentage turnover of blood (•) 

 related to uterine growth (stippled area) and intrauterine 

 pressure (x). [From Reynolds (192), based in part on Barcroft 

 et al. (20).] 



