Part 21: Female Reproducive Tract - Ovary, Oviduct, and Uterus
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Ovary with surface cuboidal epithelium. (Really a modified mesothelium.)
Cortex of ovary. A thick connective tissue capsule, the tunica albuginea underlies the surface epithelium. Somewhat deeper lie several small, primary (primordial) follicles. (All egg cells have reached the primary oocyte stage by birth and are held in this "suspended animation", in very early prophase, until such time as they may ovulate or undergo atresia.)
Primary follicles with one single layer of flat follicle cells surrounding an oocyte. Although an oocyte is a giant compared with its neighbors, this early stage is small for an oocyte, and the cell will grow considerably in size when it begins to mature, under the influence of FSH. The nucleus looks lightly granular, and the dark nucleolus is prominent. Cytoplasm is very pale. Note the "swirly" interstitial tissue of the ovarian stroma.
Early maturation stage of follicle with beginning proliferation of follicle cells around an enlarging oocyte. The nucleolus shows clearly inside the nucleus. As the oocyte enlarges, its chromosomes prepare further for the first meiotic division, which will occur at ovulation.
Further developed follicle
- a = with antrum beginning at arrows. The homogenous gray-blue line immediately surrounding the egg cell itself is the zona pellucida.
- b and c = primary follicles, containing oocytes which are still small.
A group of follicles in various stages of early development in the cortex of a rat ovary. Blood vessels of the ovarian medulla are seen in the center of the field. Development of follicles is regulated by FSH from the anterior pituitary.
Maturing follicle, so called because it contains a definite antrum (or fluid-filled space) and many layers of granulosa cells. The egg is still a primary oocyte and sits to one side of the follicle on a mound of cells called the egg hillock or cumulus oophorus. The cells closest to the oocyte will be expelled with it at ovulation as the corona radiata. Surrounding the granulosa cells of the follicle is the theca interna, a rather cellular and vascular connective tissue layer, which secretes estrogen. Outside of this is the theca externa a more fibrous connective tissue layer, not well defined here. Note that several follicles may start to develop in any one monthly cycle, but in the human only one will mature, unless there are to be multiple ovulations and therefore possible multiple births. All follicles that don't complete their maturation undergo atresia (i.e., degenerate). The egg dies, the granulosa layer breaks up, and the whole follicle collapses and undergoes fibrotic change.
Large ruptured follicle, just after ovulation.
- Arrow = stigma, the point of rupture where oocyte was expelled. The reduction division (or first meiotic division) takes place at the time of ovulation.
- a = granulosa cells that will now proliferate under the stimulus of pituitary LH and enlarge to become granulosa lutein cells, filling in the follicular cavity and becoming the major portion of the new corpus luteum.
- b = corpus albicans -- old scar of an earlier corpus luteum.
Detail of corpus luteum showing the rounded foldings of large, pale granulosa lutein cells in the lower half of the picture; these secrete progesterone. Pushing down between the folds is a wedge of smaller, darker theca lutein ; these secrete estrogen.
Detail of granulosa lutein cells with very large, pale steroid secreting cells. Their nuclei are round and granular looking, and each contains a dark, prominent nucleolus. Cell cytoplasm should be pale pink (overstained with hematoxylin here). With EM, the cytoplasm would show abundant smooth ER, as is typical of steroid secreting cells.
Corpus albicans, which is a scar of dense collagenous (white fibrous) tissue; the remnant of a degenerated corpus luteum.
Detail of corpus albicans. Nuclei represent fibroblasts.
Oviduct with highly labyrinthine mucosa. Each piece of folded, branching mucosa is lined with simple columnar epithelium. The rest of the wall is rather thin and shows interlaced smooth muscle bundles.
A higher power of the fimbriated (finger-like) end of the oviduct. The surface epithelium is high cuboidal or low columnar and has a ciliated surface. Arrows indicate non-ciliated "peg" cells which are secretory in function and stand up higher than the other cells. (a = lamina propria core of fimbria.)
A panoramic view of the uterus showing the whole thickness of the wall.
- a = endometrium (a proportionally thin layer, with a dark base as seen here.) This is a mucosa, with epithelium and lamina propria and glands.
- b = wide, dark myometrium (smooth muscle in irregular, spiralling layers). This is by far the widest layer in the wall.
- c = connective tissue perimetrium (adventitia).
- Arrows point to large blood vessels.
Dotted line represents the base of the endometrium. Menstruation is in progress, with breakdown of surface tissue.
Overview of uterine wall in the early post-menstrual stage. Only the basal layer of endometrium is present. Glands are sparse.
View of endometrium in an early proliferative stage (same magnification as the previous slide). The endometrium has grown thicker under the influence of estrogen. Glands are straight and thin.
View of a later proliferative stage. Glands are still quite straight and thin, but there is a noticeable difference between the darker, more compact basal and the paler, more edematous functional layer above.
Endometrium in the early secretory stage. Glands are becoming tortuous and sacculated under the influence of progesterone. Their glycogen-rich mucoid secretion is stored within the glands, pending a possible implantation of an embryo.
View of later secretory stage. Sacculation of glands has increased, and menstruation seems to have begun near the surface.
Endometrium in secretory (progestational) stage with sacculated glands. The thinner, non-sacculated bases of the glands will remain after menstruation, and their epithelial lining will undergo mitotic activity in order to provide the new surface epithelium for the uterine lumen.
Surface epithelium (simple cuboidal to columnar) of the uterine lining. Patches of cells are ciliated.
