396 THE GENITO-URINARY SYSTEM 



funnel is a small opening, the ostium abdominale, through 

 which the lumen of the tube communicates directly with the 

 peritoneal cavity of the pelvis, and at the margin of the orifice 

 the endothelium of the peritoneum merges into the columnar 

 ciliated epithelium of the tube. 



When ovulation occurs and an ovum is discharged from the 

 ovary, it passes at once into the general peritoneal cavity. If it 

 does not come into contact with one of the fimbriae, it is 

 absorbed, but if it does do so, it may succeed in entering the 

 ostium abdominale and it is then carried medially towards 

 the uterus by the action of the ciliae lining the uterine tube. 

 According to current beliefs, the ovum, if it is destined to 

 become fertilised, undergoes that change within the tube and 

 is then carried onwards into the uterine cavity, which is ready 

 to receive it by the time it leaves the tube. 



Ectopic Gestation. Under abnormal conditions, the 

 impregnated ovum may fail to reach the uterus, and, in that 

 event, it goes on developing in the tube, giving rise to the 

 tubal type of ectopic gestation. As the ovum enlarges, the 

 wall of the tube becomes gradually thinned out, and between 

 the sixth and eighth week it ruptures. The seriousness of the 

 condition depends on the exact site of the rupture. If the 

 rupture involves the upper surface of the tube, the peritoneum 

 covering it is also affected, and an intra-peritoneal haemorrhage 

 occurs which calls for instant surgical interference. On the 

 other hand, the lower surface of the tube may rupture and, in 

 this case, the subsequent haemorrhage occurs between the two 

 layers of the broad ligament. As a result, it is more restricted 

 in amount and the condition, though by no means trivial, is 

 not so serious. 



Just as the ostium abdominale allows the passage of the 

 ovum from the peritoneal cavity into the uterine tube, so it 

 may permit septic infection to spread directly from the tube 

 to the peritoneal cavity and, indeed, by way of the vagina, 

 uterus and uterine tube, infection may ascend from the 

 exterior to the pelvic peritoneal cavity. The presence of 



