Female Reproductive Tract - Cervix, Vagina, Umbilical Cord, Placenta, and Mammary Gland
Mucosa of the cervix with its lumen to the left. (The uterus would lie above this region and the vagina below.) Notice how the mucosal glands slant upwards. They produce a mucoid secretion. Arrows = small blood vessels.
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Sharp transition from simple columnar epithelium of the endocervix to non-cornified stratified squamous epithelium of the ectocervix and vagina.
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Vagina with stratified squamous epithelial lining and a wide lamina propria (some people would call the deeper portion of this layer the submucosa. The two connective tissue Iayers merge because there is no muscularis mucosae to separate them.) Notice distended venules in the connective tissue and the way the smooth muscle of the muscularis externa lies in loose strands. How would you distinguish this slide from a slide of esophagus?
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Vaginal smear taken during the reproductive years when the epithelium is thickest. Specifically, this smear was taken on day nine of the menstrual cycle. The large squames were removed from the surface of mature stratified squamous epithelium.
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This smear was taken on day 25 of the menstrual cycle and also shows the squames of mature stratified squamous epithelium. The numerous rod- like structures in the field are lactobacilli.
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Vaginal smear characteristically seen before puberty and after menopause, when the surface epithelium is relatively thin, either immature or atrophic. Since there are no surface squamous cells, the smear contains primarily rounded parabasal cells. Notice the presence of numerous small neutrophils with their "beady", dense, lobulated nuclei. The vagina is more prone to infections when the epithelial lining is thin.
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Both of these smears contain endocervical epithelial cells of a simple columnar, mucus-secreting type.
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Again, these are endocervical cells, but this time they are a twisted strand of ciliated epithelium.
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One of the umbilical arteries with its typically thick coat of smooth muscle. The lumen is filled with blood. Surrounding the vessel is the pale gelatinous Wharton's jelly, a specialized connective tissue with very few cells and hardly any fibers, but lots of viscous ground substance. This "jelly" contributes to the "rubberiness" of the umbilical cord, making it quite turgid and therefore unlikely to tie itself into hard knots or strangle the fetus. The umbilical cord contains two arteries and one vein.
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Low power view of the "fetal" surface of the placenta. The right-hand surface is the thick, pale pink chorionic plate. Extending to the left, from the plate, are some large, pale pink, chorionic stem villi which are seen giving off branches along their edges. All the fine pieces of tissue making up the bulk of the placenta are actually the smallest branches of the chorionic villi. What looks like empty space around them is really the intervillous space normally filled with maternal blood. The placenta, therefore, is primarily composed of fetal (chorionic) tissue (chorion frondosum) lying in a bath of maternal blood. The fetal blood flows in the vessels that you see lying in the substance of the chorionic plate and the chorionic villi, right out into the finest branchings. Such a placenta is termed hemochorial because the maternal blood (hemo-) is in direct contact with the fetal chorionic tissue (-chorial).
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Detail of thin wall of amnion, slightly detached from the chorionic plate below. The simple cuboidal epithelium of the amnion makes a smooth surface facing the fetus, which is lying in the fluid contained in the amnionic sac.
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Detail of the opposite surface of the placenta, that is, the maternal side that is eroding the endometrium of the uterus. Chorionic villi at the right are seen attaching to the thick decidual plate to the left. Large decidual cells are characteristic of this plate. They represent modified endometrial stromal cells undergoing the so-called decidual reaction during pregnancy. This plate will be sloughed off as part of the "afterbirth" at the time of parturition (expulsion of the fetus). Only the basal layer of the endometrium will remain intact after birth; it will then begin rebuilding under hormonal influences.
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Low power view of the nipple of a lactating cat, showing lobules of the mammary gland below and several narrow lactiferous ducts exiting upwards toward the surface of the nipple. The mammary gland is a compound alveolar gland derived originally as multiple epithelial ingrowths from the skin. The epithelium of its ducts and secretory units is directly continuous with the epidermis of the nipple area.
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Mammary gland (inactive): composed mostly of pale, wide, connective tissue interlobular septa with scattered lobules containing small dark cross-cuts of many intralobular ducts. There are very few, if any, secretory alveoli in the inactive gland. Much of the interlobular tissue is adipose tissue. There is one, large, interlobular duct toward the lower right corner of the field.
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Detail of one lobule of an inactive mammary gland. Note that the intralobular ducts branch frequently but have no secretory acini at their endings.
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Another view of intralobular ducts of an inactive gland. Dense connective tissue and fat cells lie in the surrounding interlobular septa. The connective tissue stroma within the lobule is more cellular than the interlobular connective tissue outside.
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Mammary gland (proliferating in pregnancy) with the lobules now enlarging as secretory acini sprouts from the intralobular duct systems. The septa (pale pink) are becoming compressed. Note large interlobular ducts lying in the septa. Lobules now seem more comparable to the kind of thing seen in the salivary gland. Secretion of watery cholostrum precedes the secretion of true milk, which does not come until after the birth of the child.
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Diagram of inter-relationships between the anterior pituitary, ovary and uterus during the menstrual cycle. Beginning at the upper left, the ovarian follicle enlarges under the influence of high titers of FSH from the pituitary. As the follicle grows, its theca interna produces increased amounts of estrogen which causes the endometrium below to thicken. During this proliferative phase, the endometrial glands are thin and straight and the coiled arteries increase in length. At mid-cycle (about 14 days) there is a great surge of LH from the pituitary, coinciding with the time of ovulation. The follicular epithelium that remains behind undergoes a marked hyperplasia and differentiates into granulosa lutein cells, which form the bulk of the new corpus luteum. Under the influence of pituitary LH, these cells now produce progesterone which, in turn, causes the endometrium to thicken somewhat further and develop very wide, tortuous, sacculated glands, ready for implantation by an ovum. Estrogen is still being produced by the theca interna. At about 28 days, if there is no implantation, the titers of estrogen and progesterone fall off as the corpus luteum degenerates, and, at the same time, the coiled arteries of the endometrium clamp down. Thus deprived of nourishment, the endometrium begins to break up and slough off in menstruation. Only the basal layer of the endometrium will remain. Hormonal feedback now tells the pituitary to increase its secretion of FSH, thus starting the cycle all over again. In the event of pregnancy, of course, the corpus luteum is preserved, the production of estrogen and progesterone remains high, and the glandular endometrium is maintained. In time, the developing placenta itself produces an LH-like chorionic gonadotropin and, later, both estrogen and progesterone, in order to maintain the appropriate hormonal environment for the developing fetus and its needs.
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Detail of secretory acini of the proliferating mammary gland. An intrabular blood vessel is evident in the upper left quadrant of the field.
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Lactating mammary gland with alveoli (acini) very distended with milk secretion, which stains bright pink here. Notice the branching, tubular shapes to some of the secretory units. The lobule to the right has emptied its contents. Notice how thin and compressed the interlobular connective tissue septa are now (very thin, pink strands around groups of the empty alveoli).
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