The pregnant uterus was found to exert pressure upon the lumbar region with a maximum over the midline of the lordosis and diminishing laterally. Those parts of the arterial system formed by the aorta and its dorsal branches and displaceable at autopsy, were accordingly dislodged by the uterus, whereas the fixed parts were compressed. The pressure effects extended cranially during pregnancy. Symptoms of compression can be relieved by avoiding supine and prone positions.
To study in the human the conditions for the flow regimes inherent in urinary systems with a dependence of the contraction interval on urine flow rate (boluses-in-contact, leaky-bolus, and open-tube flow regimes), 50 urinary systems were examined at low and high flow rates. Morphometry and volumetry were applied to eight urinary systems. The bolus frequently contacted the preceding contraction ring but the mechanisms differed categorically from that conventionally postulated. Thus the contraction interval proved independent of flow rate, leading to boluses in contact not only at high but also at low flow rates, which is impossible in flow-dependent urinary systems. Likewise, contact proved possible with small as well as large boluses. Furthermore, the contact was invariably interrupted at the points of resistance to flow, the total contact period being only 4% of the ureteral transit. Leaky-bolus flow and open-tube flow were absent. The flow regimes as conventionally defined thus proved to be absent from and inconsistent with normal human urinary transport.
The recognition of certain anatomic relationships in the abdomen is a prerequisite for an analysis of the changes occurring there in pregnancy. These relationships have therefore been investigated by the roentgen examination of the ovarian vessels and the ureter, and by dissection of the organs and structures of the posterior abdominal wall with special reference to their mobility. Dissections were performed by LEONARDO DA VINCI in about 1510 and documented in a series of drawings that depict the ovarian vessels passing in a straight course medial to the ureter and in front of the external iliac vessels to the ovary where they turn inwards to the uterine horn; both vessels are single. HUNTER (1774, 1794) demonstrated the anastomoses of the ovarian, uterine and round ligament vessels in pregnancy and, in an investigation of the nerve supply of the uterus in non-pregnant subjects, dealt with the connective tissue sheath surrounding the ovarian vessels in the posterior abdominal region. SOULIGOUX ( 1894) described the ovarian artery as being tortuous along its entire course and the vein as consisting of several branches in the pelvis forming a single straight vessel at the pelvic inlet. The ovarian vessels in text-books of anatomy (CUN-
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