86 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



contraction of the tube muscle, caused by handling and cutting. 

 In the infundibular and ampullary segments of the tube, the 

 mucous membrane is thrown into long plicated folds shown in 



rd. lig. uter. 



'allopian tube 

 plicae 

 'olffian duct 

 mesosalpinx 

 mesouarium 

 ouaru 



Fig. 64.— Diagrammatic section of .the Broad Ligament and Fallopian Tube. 



section in Fig. 64. They are covered with ciliated epithelium, 

 which urge the ovum towards the uterus. Within the tube 

 impregnation usually takes place. If an obstruction arrests the 

 fertilized ovum in the tube, perhaps it may be a patch denuded 

 of epithelium and cilia by gonorrheal inflammation, a tubular 

 pregnancy is the result. The growing embryo, commonly about 

 the second month, bursts the tube and falls within the broad liga- 

 ment or into Douglas's pouch (Fig. 64). 



The History of the Ovum within the Fallopian Tube.— 

 When the ovum enters the Fallopian tube, it is a cell of very 

 considerable size ('2 mm. = -jhs in.) with a cell wall — the zona 

 radiata (Fig. 63), a nucleus — the germinal vesicle, and a nucleolus 

 — the germinal spot. Then, or before then, the ovum prepares 

 for fertilization by the extrusion from its nucleus of first one, 

 then another polar body, and, with the extrusion, the germinal 

 vesicle becomes the female pronucleus. The polar bodies, which 

 lie outside the protoplasm of the ovum, but within the zona 

 radiata, are parts of the germinal vesicle, which are extruded 

 with all the display of karyokinesis (Fig. 65 A). The meaning 

 of the process has been much guessed at ; the outstanding fact 

 is that two parts of the ovum are segregated and are not 

 involved in the subsequent developmental changes. What , 



