(Transcribed from Dr. Kalliecharan’s lecture, 3 April 2000 by Brian Buschman)
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The oviduct is the muscular tube that has one end connected to the uterus and one end open near the ovary for the sake of moving the oocyte. The oviduct begins at it’s infundibulum which has fimbriae that catch the oocyte and direct it into the tube. It then continues as the ampulla, the isthmus and finally the intrauterine part. If you remember from January fertilization usually happens in the isthmus.
The oviduct has three layers:
1) The mucosa has longitudinal folds and two types of simple columnar cells.
a. Ciliated cells, most of which beat towards the uterus, but the cilia are not essential for oocyte transport. In the case of immotile cilia syndrome oocyte transport is not slowed.
b. Non-ciliated (peg) cells which secrete a fluid that nourished the sperm and encourages capacitation. The fluid also washes towards the uterus which slows the travel of microorganisms up the tube to help prevent them from entering the peritoneal cavity via the oviduct.
The epithelia hypertrophies in the follicular phase and atrophies in the luteal phase of the menstrual cycle.
The epithelia also has a lamina propria of loose connective tissue.
2) Muscularis externa with an inner circular and outer longitudinal muscle layers.
3) The outer layer is a serosa (i.e. has a mesothelium).
The uterus is made of three layers, the perimetrium (externally), myometrium (middle) and endometrium (internally).
1) The perimetrium is the external layer which is either a serosa or adventitia depending on location.
2) The myometrium is the muscular component of the uterus. It has four poorly defined layers. The inner and outer are longitudinal and the two middle layers are some degree of circular and/or oblique. The middle two layers contain the vascular supply.
Pregnancy leads to hypertrophy and hyperplasia of the myometrium to make more room for the developing baby. They also actively secrete collagen. After pregnancy it atrophies to get back to a normal size.
3) The endometrium has a simple columnar epithelia that has some cells that are ciliated and some secretory. The simple tubular glands are mostly lined by secretory cells. It has a lamina propria with lots of ground substance and lots of fibroblasts. It needs lots of fibroblasts to be able to make large amounts of connective tissue when it enlarges with pregnancy.
The endometrium has to parts, the functionalis, which is sloughed off monthly, and the basalis which is not. The roots of the glands are located inside the glands of the basalis so they are not lost every month.
The endometrial blood supply is by two types of arteries. Straight arteries that supply the basalis and coiled arteries that supply the functionalis.
The cervix is the lower part of the uterus that connects it to the vagina. It has an epithelium made of mucus secreting simple columnar cells. The mucosa has cervical glands that secrete mucus. During pregnancy and when the menstrual cycle is not near ovulation the cervical glands secrete a more viscous mucus that helps somewhat close the opening of the cervix. This helps prevent the spread of infection into the uterus. Near ovulation the secretions are more viscous to allow the sperm to pass.
The walls of the vagina have no glands and are made of non-keratinized stratified squamous epithelia. They have three layers:
1) The epithelium. It accumulates glycogen and releases it into the lumen. The glycogen feeds vaginal bacteria which produce lactic acid. The acid is what lowers the pH of the vagina and help protect the vagina.
2) A thin muscular layer. It has a few scattered inner bands of circular smooth muscle but the almost all of it appears longitudinally arranged.
3) An outer adventitia.
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