The uterine tubes (also called Fallopian tubes or oviducts):
The uterine tubes can be divided into three major parts:
|The infundibulum (in-fun-DIB-u-lum) is the region most proximal to the ovary. It is funnel-shaped and has finger-like projections called fimbriae (FIM-bre-e) that extend into the pelvic cavity and make close contact with the ovaries. The tunica mucosa occupies most of the thickness of the wall of the organ.||The ampulla is the middle, one-third region in which fertilization usually occurs. Histologically it is very similar to the infundibulum having a very thick tunica mucosa and relatively thick tunica muscularis.||The thick-walled isthmus is the lower one-third region most proximal to the uterine horns. The smooth muscle in the wall of the isthmus helps propel (by peristalsis) the fertilized ovum toward the uterine horns and body of the uterus where implantation occurs. The tunica muscularis is the thickest part of the wall and the tunica submucosa is very thin as in the infundibulum and ampulla.|
About the time of ovulation, the infundibulum, closest to the ovary, moves to cover the site of rupture of the mature (Graafian) follicle.
The ovum moves down the infundibulum of the uterine tube toward the ampulla, assisted by peristaltic contractions of the smooth muscle in the wall of the tube as well as fluid moved by ciliated epithelial cells in the mucosa of the tube. The ampulla is usually the site of fertilization.
After fertilization, the embryo moves down through the isthmus which connects the uterine tube with the uterine horns or uterus. The thick muscular wall of the isthmus of the uterine tube helps propel the embryo into the uterus where it can be nourished during further development.
|The uterine tubes are paired tubular organs
with the typical organization of a tubular organ, i.e., four tunics consisting of:
The thickness and specific characteristics of these tunics varies with
the region of the uterine tube.
|The tunica mucosa of the infundibulum helps
capture the ovum from the surface of the ovary, bathes it in a supportive fluid and helps
move it toward the uterus.
The tunica mucosa of the ampulla provides the proper environment for fertilization.
Consequently, in the infundibulum and ampulla the tunica mucosa is thick and highly developed.
|It is the tunica muscularis of the isthmus
that provides the strong contractions that at the right time propel the ovum or embryo
into the uterine horns.
As a result, in the isthmus the tunica mucosa is reduced in thickness and the tunica muscularis is much thicker
|Light micrographs of uterine
The lamina epithelialis of the tunica mucosa of the uterine tubes is an intermittently ciliated columnar epithelium that contains two types of cells: a ciliated cell and a non-ciliated, secretory cell. In the cow and sow the lamina epithelialis may be pseudostratified intermittently ciliated columnar. The secretory product of the non-ciliated, secretory cells is moved toward the uterine horns by the movement of the cilia on the ciliated cells. This secretion probably also protects and nourishes the ovum.
The lamina propria consists of a typical loose areolar connective tissue without glands, and it blends with the underlying, thin tunica submucosa. There is no lamina muscularis mucosae in the entire female reproductive tract. The tunica muscularis is sparse in the infundibulum and the ampulla but thick in the isthmus consisting of an inner circular and an outer longitudinal layer of smooth muscle. The tunica serosa is typical containing many blood vessels in a distinct vascular layer.
here to see the Uterine tube Histology slides.
|Scanning electron micrographs of a
uterine tube from a sow.
|Click here to see more SEM images of a uterine tube from a sow.||More scanning electron micrographs of a
uterine tube from a sow.
Cyclic Changes in the Epithelium : Under the influence of estrogen, the ciliated epithelial cells increase in height and in the number of cilia. Under the influence of progesterone, these cells decrease in height and in the number of cilia. These cells are at their tallest with the most numerous cilia at the time of ovulation. Their main function is to assist in the movement of the ovum toward the site of fertilization and the embryo toward the uterus. This action is secondary to the peristaltic movement of the isthmus region.
Clinical: The uterine tubes are the site of tubal ectopic pregnancies. They can also be the site of bacterial infection which can lead to Pelvic Inflammatory Disease, a major cause of infertility in women.