Abstract
The region connecting the uterus and the vagina of the fowl oviduct was studied histologically and histochemically. It was found that there were a special mucosal zone at the caudal end of the uterus and another at the beginning of the vagina. Each zone was characterized by the following structures.
1. The caudal end of the uterus forms a ring shaped zone, about 0.5-1cm wide, immediately before the vaginal orifice. It is covered with a grayish-white mucous membrane and has low, somewhat longitudinally arranged mucosal folds. These folds differ from those of the main portion of the uterus, which are leaf-like and faintly pinkish in color. This zone is usually distinguished by the mucosal color, which is variable according to the functional activity of the oviduct. The histological feature of this zone is the presence of small tubular glands which are different from the uterine glands and which are scattered in the stroma of loose connective tissue of the mucosal lamina propria. The histochemical feature of the zone consists in the deposition of cholesterin ester lipid in its covering epithelium. The deposited lipid varies in quantity according to the activity of the oviduct. Generally, it is abundant in a stage when there is no egg in the oviduct, but it is quite scanty immediately after the expulsion of an egg.
2. The beginning of the vagina forms an area, about 1cm far from the vaginal orifice, which is greater in diameter and which has lower and wider mucosal folds than the other portions of the vagina, the most striking histological feature of this zone is the presence of large tubular glands, which are called the vaginal glands. Histochemically, the glandular cells of the vaginal gland is characterized by the presence of a large amount of cholesterin ester lipid. The functional change in the amount of this substance in the vaginal gland cells is the same as in the preceding uterine covering epithelium.
3. The function of the glands at the caudal end of the uterus and at the beginning of the vagina could not be clarified. Judging from their position and functional activity, these glands seem to contribute to the formation of the cuticle layer of egg shell.
4. The deposition of cholesterin ester lipid in the two parts mentioned above is the most outstanding feature of the region of the uterovaginal juncture. This substance seems to play some role in the formation of the cuticle layer, since it is discharged when the egg is laid.
