1122 



SUBMAMMALIAX VERTEBRATES 



4. The Oviduct 



A discussion of the effects of the ovarian 

 hormones on the development and function 

 of the avian oviduct requires a brief ana- 

 tomic description of this organ. The second- 

 ary sex organ of female birds usually con- 

 sists of a single fully developed, left oviduct 

 which has developed from the Miillerian 

 ducts. Even in species in which the inci- 

 dence of two ovaries is high, only one ovi- 

 duct is developed (Witschi and Fugo, 1940; 

 Nelson and Stabler, 1940; von Faber, 1958 j. 

 In chickens the incidence of right oviducts 

 varies between different strains, but, in a 

 large number (80 to 85 per cent), some 

 evidence of a right oviduct is encountered 

 (Winter, 1958). Morgan and Kohlmeyer 

 (1957) reported that the incidence of fully 

 developed right oviducts was quite high in 

 one inbred strain of chickens. Usually, how- 

 ever, the right oviducts are thin mem- 

 branous cysts or short tubes (Winter, 1958). 

 Development of right oviducts can be in- 

 duced by estrogen treatment of the embryo, 

 a topic discussed in the chapter by Burns. 

 It is, thus, possible that the higher incidence 

 of fully developed right oviducts in certain 

 strains is the result of a higher estrogen 

 deposition in the yolk and the consequent 

 presence of abnormal quantities of estrogen 

 in the developing embryo. This explanation 

 is speculative, but may be worth further 

 investigation. 



The left o\'iduct is suspended from the 

 body wall by the dorsal and ventral liga- 

 ments. The ventral ligament, at its caudal 

 end, consists of muscle fibers radiating to- 

 wards the vagina. The left dorsal oviducal 

 ligament, the left abdominal air sac, and 

 the body wall together form the "ovarian 

 pocket" (Surface, 1912) into which the 

 yolk falls after ovulation. The oviduct 

 subsequently engulfs the yolk and trans- 

 ports it to the cloaca. 



The oviduct can be divided into 5 ana- 

 tomically distinct regions which will be de- 

 scribed from an anatomic and functional 

 point of view. 



1. The injundibuhim is about 7 cm. long 

 and consists of a thin funnel. Its lips are 

 continuous with the ventral and dorsal 

 ligaments (Surface, 1912) ; the chalaziferous 



region if^ tubular in shape (Richardson, 

 1935; Winter, 1958j. The infundibular walls 

 are comjjosed of the peritoneum, a thin layer 

 of longitudinal muscles, and a nonciliated 

 columnar epithelium. In the funnel the epi- 

 thelium consists of nonciliated and ciliated 

 cells; in the chalaziferous region goblet cells 

 filled with mucin are also present (Richard- 

 son, 1935; Winter, 1958). The mucin cells 

 stain with mucicarmine, thionin, hematoxy- 

 lin, and Bismarck brown. Although the main 

 function of the funnel is to engulf the egg, 

 some mucin is deposited around the yolk 

 while it descends the oviduct. Van Drim- 

 melen (1951) identified the "sperm nests" 

 in the infundibulum. Although a part of the 

 infundibulum has been named the chalazi- 

 ferous region, the chalazae are not formed 

 there nor is the material from which they 

 are formed secreted there. Burmester and 

 Card (1939) resected this region of the 

 oviduct and found no significant decrease 

 in chalazae weight as a result of the re- 

 section. 



2. The infundibulum gradually changes 

 into the iiKigninn which is about 34 cm. long 

 in an active oviduct. It has thicker walls 

 than the infundibulum, mainly because of 

 enormously developed tubular glands which 

 secrete albumen. The magnum is character- 

 ized by nuicosal ridges with secondary and 

 tertiary folds, and by an epithelium consist- 

 ing of ciliated cells and of nonciliated goblet 

 cells filled with mucin. The staining af- 

 finities of the goblet cells are similar to those 

 of the infundibulum. The function of the 

 magnum is mainly the secretion of the 

 thick albumen around the yolk. This proc- 

 ess is completed in the relatively short time 

 of 3 to 4 hours (Warren and Scott, 1935). 



3. The transition of magnum to isthmus 

 is marked by a sharp band visible to the 

 naked eye. This band is free of tubular 

 glands and is covered by a cuboidal epi- 

 thelium. The isthmus is about 8 cm. long 

 and has a thin tubular gland layer result- 

 ing in a thinner wall than the magnum. 

 These glands of the isthmus secrete ovokera- 

 tin for the formation of the shell mem- 

 branes, a process which occurs during the 

 1-hour sojourn of the egg in the oviduct 

 (Warren and Scott, 1935). Histologic ex- 

 amination reveals a circular muscle layer 



