BV, blood vessels CT, connective tissue FC, former follicular cavity GLC, granulosa lutein cells TC, granulosa cells transforming into corpus luteum cells TLC, theca lutein cells KEY 878 The uterine tubes (oviducts, Fallopian tubes) are joined to the uterus and extend to the ovaries, where they present an open flared end (abdominal ostium) for entry of the ovum at ovulation. The oviduct undergoes cyclical changes along with those of the uterus, but these are not nearly as pronounced. The epithelial cells increase in height during the middle of the cycle, just about the time the ovum will be passing through the tube, and become reduced during the premenstrual period. Some of the epithelial cells are ciliated. The epithelial cells depend on the ovaries for their viability. Not only does the number of ciliated cells increase during the follicular phase of the ovarian cycle, but also removal of the ovaries leads to atrophy of the epithelium and loss of ciliated cells. The uterine tube varies in size and degree of mucosal folding along its length. The mucosal folds are evident in its distal portion, the infundibulum, as it nears the open end. Near the opening, the tube flares outward and is called the infundibulum. It has fringed folded edges called fimbria. The infundibulum leads proximally to the ampulla, which constitutes about two thirds of the length of the oviduct, has the most numerous and complex mucosal folds, and is the site of fertilization. Mucosal folds are least numerous at the proximal end of the oviduct, near the uterus, where the tube is narrow and referred to as the isthmus. A uterine or intramural portion measures about 1 cm in length and passes through the uterine wall to empty into the uterine cavity. Fertilization of the ovum usually occurs in the distal portion of the ampulla. For the first several days of development, as it navigates the complex pathway created by the mucosal folds, the embryo is transported proximally by the beating of the cilia of the ciliated epithelial cells and by peristaltic contractions of the well-developed muscularis layer that underlies the mucosa.
Uterine tube, human, H&E ×40.
A cross section through the ampulla of the uterine tube is shown here. Many mucosal folds project into the lumen (L), and the complicated nature of the folds is evident by the variety of profiles that is seen. In addition to the mucosa (Muc), the remainder of the wall consists of a muscularis (Mus) and connective tissue.
The muscularis consists of smooth muscle that forms a relatively thick layer of circular fibers and a thinner outer layer of longitudinal fibers. The layers are not clearly delineated, and no sharp boundary separates them.
Mucosal fold, uterine tube, human, H&E ×160; inset ×320.