Uterus -- site of implantation and growth of embryo.

Clinical note: Smooth muscle cells of the uterus commonly give rise to benign tumors called leiomyomas or fibroids, which usually do produce major medical problems but grow slowly and often attain diameters of several centimeters.

Examine a trichrome-stained section of uterus (slide 1) and identify the

• Endometrium,
• Myometrium,
• Perimetrium with serosa, and
• The attached connective tissue.

Examine the endometrial surface (Fig. 22-14) and note the simple columnar epithelium. Throughout the endometrium, identify endometrial glands and vascular sinuses in the stroma. You may be able to distinguish the basal layer and functional layer of the endometrium, but this is difficult on slide 1. In the myometrium, observe the interlacing bundles of smooth muscle fibers (Fig. 22-14).

How do the secretory, highly vascular, and muscular aspects of the uterus interact as this organ functions?

How does the endometrial stroma differ physiologically from other examples of connective tissue?

Clinical note: Endometriosis, a common medical problem of the female reproductive system, results when sloughed endometrial tissue is refluxed up the uterine tubes and surviving cells begin to grow on the surface of the ovary, mesenteries, or other organs in the peritoneal cavity. Cycles of growth and loss of this displaced endometrial tissue occur under the influence of estrogen and progesterone, which can eventually result in inflammation, pain, and scarring of the affected organs. Untreated, endometriosis can lead to infertility for several reasons.

Now let's look at the stages of endometrial deleopment.