Uterus
About the Uterus
The uterus is a pear shaped muscular organ approximately 7.5 cm long in nonpregnant women, expanding to 30 cm during pregnancy. It has three layers: perimetrium outer, myometrium thick smooth muscle, and endometrium inner lining that thickens and sheds during menstruation. The fundus is the top, body is the main portion, and cervix connects to the vagina. Endometrial cycle: menstrual days 1 to 4, proliferative estrogen days 5 to 14, secretory progesterone days 15 to 28. Menstruation occurs when progesterone drops without pregnancy. Implantation occurs 6 to 7 days after fertilization. Fibroids, benign smooth muscle tumors, are very common, affecting a large proportion of women by age 50, though many cause no symptoms. Endometriosis is endometrial tissue outside the uterus causing pain and infertility.
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