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Lab 17. Female Reproductive Tract 1

Objectives

Identify the components of the female reproductive tract (ovary, oviduct, uterus, vagina and breast) and recognize structural changes which occur during the menstrual cycle or pregnancy

Ovary

The ovaries (slide #79) are paired gametogenic and endocrine glands. Each ovary consists of a cortex containing follicles with oocytes and a medulla with prominent blood and lymph vessels. Examine both odd and even slides of the ovary. The flattened or cuboidal germinal epithelium (mesothelium) on the surface of the ovary is easily torn loose and is often missing (best seen on #79 even). Underlying the germinal epithelium is the tunica albuginea which consists of a thin layer of dense, circular connective tissue with fibers running roughly parallel to the surface. The deeper cortical area contains the follicles. The cortical stroma is highly cellular, and the elongated stromal cells are arranged in wavy patterns or whorls.

Examine the blood vessels in the medulla. The lymphatic vessels are particularly prominent on slide #79 odd, and can be distinguished on the basis of their fluid content (few leukocytes and no RBCs), their thin walls, and the presence of valves projecting into the lumen. Compare their walls with those of veins which are also present and contain RBCs.

A. Follicles

Follicles of all sizes are found in the ovary of a reproductively active woman. Slide #79 odd is the ovary from an older woman and contains some primordial follicles, a few secondary (vesicular) follicles and many late atretic follicles. The monkey ovary on slide #79 even contains follicles at various stages of development. It may contain several primary (growing) follicles with two or more oocytes. These are common in monkey ovary but very rare in human ovary. Many of the follicles are undergoing atresia. You may have to use atretic follicles for examples of different stages of follicular development. Using slides #79 odd and even find:

1. Primordial follicles

The small primordial follicles measure about 30 Ám ( the diameter of four to five RBCs) and have a single flattened layer of follicular cells around the oocyte.

2. Primary follicles (growing solid follicles)

When follicle growth begins, the flat follicular cells become cuboidal. The zona pellucida begins to form between the oocyte and the follicular cells. The follicular cells become multilayered, and the surrounding stromal cells begin to form the theca interna and the theca externa. The boundary between the two theca layers is indistinct and the theca externa blends into the surrounding stroma.

3. Secondary follicles (vesicular)

When follicles reach about 200 Ám in size, pools of fluid begin to accumulate between the follicular cells (granulosa cells) and these eventually coalesce into one central mass of follicular fluid in a space called the antrum. The oocyte then lies to one side of the follicle. Pick out a late secondary follicle, preferably one in which the oocyte has been included in the section. Starting with the oocyte, find the zona pellucida. The several layers of follicular cells forming a hillock and encompassing the oocyte constitute the cumulus oophorus. The follicular basement membrane separates the nonvascular follicular cells from the vascular theca cells. The theca cells closest to the follicular basement membrane have enlarged and differentiated into steroid secreting cells. These constitute the theca interna and may form more than one layer in some areas around the follicle and be absent in others. Further out, where the cells gradually appear more flattened but are still oriented around the follicle is the theca externa. The theca externa is often poorly developed and gradually blends with the multi-oriented interstitial cells of the ovarian stroma. Arterioles and venules may be seen primarily associated with the theca externa, while a capillary network is found in the theca interna.

 

4. Mature follicle (Graffian follicle)

In mature follicles antrum and follicle are maximally developed (2.5 cm). The follicle extends through the full thickness of the cortex and bulges from the surface of the ovary. There are no mature follicles on these slides.

B. Atretic Follicles

Few follicles, grow up to the point of ovulation. Most begin to grow and then degenerate. In young follicles the oocytes degenerate first. In secondary follicles, early changes include the presence of follicular cells floating in the antral fluid and the invasion of fine blood vessels and connective tissue into the granulosa cell layer. In these follicles the granulosa cells degenerate first, then the oocyte; the degenerating tissue is replaced by connective tissue, macrophages, and capillaries. The follicle collapses, and the follicular basement membrane becomes wavy and thickens into a mass of hyaline (i.e., refractile) material called the glassy membrane. Locate the glassy membrane, a wavy, refractile, pink-staining line, usually U-shaped or circular. This and its associated cells are terminal remnants of atretic follicles. The process of atresia can take several months.

C. Corpus Luteum

A mature follicle extends throughout the thickness of the cortex, pushes into the medulla and forms a bulge on the surface of the ovary. At ovulation the follicle ruptures and extrudes its oocyte surrounded by its zona pellucida and corona radiata cells. Bleeding into the antrum occurs and the follicle shrinks and collapses, throwing the theca and granulosa layers into folds. This structure, called the corpus hemorrhagicum, increases in size and the cells undergo mitosis and morphological changes (luteinization). It is then called a corpus luteum of ovulation (menstruation or spurium). If fertilization occurs, there is further enlargement to form a corpus luteum of pregnancy (graviditatis or verum).

The corpus luteum of slide #80 is a body about one inch in diameter with an angular cavity. With the reverse ocular or naked eye, examine its shape and size. With 10x, note that the granulosa lutein cells derived from the follicular (granulosa) cells are the predominant and largest cell type.

   

The theca lutein cells, derived from the theca interna, are smaller, fewer in number, and are located peripheral to the granulosa lutein cells. Groups of these cells may be seen where there are connective tissue infoldings. They appear as groups of crowded rounded nuclei with empty looking cytoplasm (best seen on #80 odd). Under higher magnification, compare the granulosa lutein cells with the theca lutein cells. Note the abundance of capillaries among both cell types. At the end of menstruation, the corpus luteum involutes, its cells degenerate, yellowish lipochrome pigment is seen, and the area is invaded by fibroblasts and macrophages. Over the succeeding months, these cells become pyknotic, and the area is eventually changed into a pale scarred mass called the corpus albicans (white body). This sinks deeper into the ovary over months or years. On slide #81, examine a large, fairly recent corpus albicans still reflecting the shape of the corpus luteum. On slide #79 odd (ovary), a small, shrunken, more fibrous, and hence, older corpus albicans may be found.

Oviduct (Fallopian or Uterine Tube)

The oviducts are paired tubes extending from the ovary to the uterus. They are enclosed within a fold of peritoneum. The oviduct consists of (a) an enlarged funnel-shaped region called the infundibulum, (b) a tubular portion called the ampulla, (c) a constricted portion called the isthmus, and (d) the intramural region which passes through the uterine wall. The oviduct undergoes gradual morphological changes from the infundibulum to the intramural portion. This includes a decrease in the size of the lumen a decrease in branched folds and a thickening of the muscle coats. The epithelium consists of ciliated columnar cells and non-ciliated secretory (peg) cells. The ciliated cells are most abundant at the infundibulum, and their relative number decreases gradually towards the uterus. The height of the epithelium varies during the menstrual cycle, being greatest during the proliferative phase.

Just prior to the extrusion of the oocyte from the ovary, it completes the first meiotic division and arrests at metaphase of the second meiotic division with the haploid number of chromosomes. It is now called a secondary oocyte and enters the oviduct. Fertilization usually occurs at the junction of the ampulla and isthmus.

A. Infundibulum and Ampulla

Slide #83 (even and odd) both contain sections of infundibulum and ampulla. It can be difficult to tell where the infundibulum ends and the ampulla begins. Slide #83 odd is a longitudinal section through the infundibulum and ampulla. Since the tube is twisted, portions of the tube may be in oblique or cross-section. With the reverse ocular or scanning lens, locate the infundibulum with its fimbria at the extreme end of the tissue. At the opposite end is the ampulla. Notice the gradual decrease in size of both the lumen and the mucosal folds and the gradual increase in the thickness of muscle coat. Examine the epithelium and notice the patches of ciliated cells.

On slide #83 (even) find the large, funnel-shaped infundibulum. The muscle wall may be present on only one side. On the other side are large, highly branched mucosal folds (fimbria). Locate the ampulla. The mucosal folds are branched and prominent. The epithelium has abundant patches of ciliated cells. The lamina propria and serosa are vascular and the muscle wall thin.

B. Isthmus

On slide #82 (odd and even), find the cross-section of the isthmus (round in outline) and note that the folds of the mucous membrane are relatively simple, and their lamina propria is very vascular. The mucosal folds are covered by columnar epithelium with only a few ciliated cells. The muscle wall is conspicuous with a thick inner circular and a thinner outer longitudinal component. At the outer edges of the oviduct, locate the covering serosal epithelium (may be absent), and note that the serosa is thick and contains abundant blood vessels.

C. Intramural

The intramural (interstitial) portion of the oviduct is found within the myometrium of the uterine wall. Using the scanning lens, find on slide #82 (even, up to box #186 only) the small lumen of the intramural duct, which is lined by columnar epithelium. There may be blood vessels nearby in the uterine tissue with a lumen as large or larger lined by squamous epithelium. Note the size of the oviduct lumen, the near absence of mucosal folds and under higher magnification, the scarcity of ciliated cells. The intramural oviduct is encircled by its own muscular coat which can be distinguished from the multi-oriented uterine muscle. This slide also contains a section through the isthmus.

Uterus

The uterus is a muscular, pear-shaped organ composed of the body, the isthmus and the cervix. The uterine mucosa is called the endometrium, the muscle layer is the myometrium, and the serosa (over the fundus and posterior surface) or the adventitia is the perimetrium.

A narrow portion of the endometrium adjacent to the myometrium is not shed at menstruation and is called the stratum basalis. Cells from the glandular epithelium, stroma and blood vessels of the stratum basalis proliferate and restore the endometrium after menstruation. The more superficial and thicker layer of the endometrium, which is formed after menstruation, is called the stratum functionalis.

The blood supply of the endometrium comes from the circumferentially oriented arcuate arteries of the myometrium. Branches from these arteries pass to the endometrium and form the straight arteries which supply the stratum basalis and the coiled (spiral) arteries which supply the stratum functionalis. The straight arteries do not undergo cyclic changes, and the constant blood supply to the stratum basalis contributes to its stability. Before the onset of menstruation the coil arteries constrict causing ischemia and destruction of the stratum functionalis. At menses the stratum functionalis is shed. At the end of menses the proliferative or follicular phase begins.

A. Menstral Cycle

1. Proliferative Phase

Examine a uterus in the proliferative or follicular phase on slide #85. (Slide #85 is late proliferative). With the reversed ocular, locate the endometrium and choose an area where the glands appear to be cut in longitudinal section. Examine the full thickness of the endometrium noting that the stroma is more compact towards the stratum basalis. Under higher magnification, note that a columnar epithelium (with a few scattered ciliated cells) lines the surface and the glands. The glands are straight or slightly wavy. The myometrium is composed of three indistinct layers of muscle.

2. Secretory Phase

Examine a uterus in the secretory or luteal phase (slide #86), both odd and even should be seen. With the reversed ocular and higher magnification, locate the endometrium, (on one side of the tissue block) with its characteristically dilated or sacculated glands. Under higher magnification notice that the stroma is edematous (increased interstitial fluid) in slide #86 odd, and shows large empty spaces. Immediately adjacent to the myometrium, the bases of the glands are located in the stratum basalis.

3. Menstrual Phase

Slide #87 even is a late menstrual uterus. The free surface of the endometrium has lost its epithelium, and the stroma and broken glands and blood vessels protrude. Little remains of the stratum functionalis. Most of the glands and stroma belong to the stratum basalis and will not be shed. There is no evidence of epithelialization of the denuded surface, so this section was taken before the end of the menstrual period. Slide #87 odd is of a menstrual uterus just after the beginning of menstruation. In some areas the epithelium is still intact though the underlying stroma is swollen with extravasated blood.

B. Cervix

Slide #88 (odd and even), is a section through one side of the cervix. The lumenal surface of the endocervix (region of the cervical canal) is lined with columnar epithelium. At or near where the tissue curves (region of the external os) the epithelium changes from simple columnar to stratified squamous (region of the ectocervix). The highest incidence of gynecological cancers occurs in the region of the external os. In the region of the endocervix, there are several cervical glands (these are best seen on slide #88 odd). Some glands project under the stratified squamous epithelium of the ectocervix and may show cystic dilations. The muscle of the cervix is relatively deficient compared to the rest of the uterus and arranged in irregular bundles and intermingled with dense connective tissue. Note the abundance of blood vessels.

C. Vagina

The vagina is a distensible fibromuscular tube continuous above with the cervix and opening into the vestibule of the female external genitalia. The wall of the vagina consists of three layers: mucosa, muscularis, and adventitia. Slide #89 has only the mucosa and part of the muscularis.

The mucosa consists of an epithelium and a lamina propria. A muscularis mucosa is absent. Examine the noncornified stratified squamous epithelium (note nuclei at all levels). The epithelial cells accumulate glycogen and in routine H & E sections they appear vacuolated since the glycogen is dissolved during slide preparation. The lamina propria consists of thick, dense connective tissue with varying numbers of leukocytes. Elastic fibers are plentiful beneath the epithelium but cannot be differentiated with H & E stains. Glands and gland openings are lacking. The lamina propria contains many blood vessels.

The smooth muscle of the muscularis is arranged in interlacing bundles, which do not occupy well defined layers. In a few slides, striated fibers are present in the outer muscle coat.

Mammary Gland

The fully developed mammary gland is a compound tubulo-alveolar gland which consists of 15 to 25 lobes. Each lobe is composed of the ducts and alveoli which drain into one lactiferous duct. The degree of glandular development depends on the sex, age, and the functional condition of the reproductive system. In the sexually mature, non-pregnant female, the glands consist primarily of a duct system embedded in a large amount of fat and connective tissue. When pregnancy occurs, the duct system undergoes proliferation and secretory alveoli develop from the ends of the duct branches. This growth continues throughout pregnancy so that much of the fat and connective tissue is replaced by secretory alveoli at parturition.

A. Non-lactating Mammary Gland

Slide #91 -(NOTE: on slide #91 odd, there is a large encapsulated area with loose connective tissue, degenerated glands, and enlarged cystic ducts and glands. This is a fibroadenoma. Study the rest of the tissue which is normal). The lobes of the mammary gland are further subdivided into lobules. On slide #91 locate the lobules which are separated by dense interlobular connective tissue and fat cells. The epithelial cells within the lobule are chiefly duct elements and are contained in a loose connective tissue which lacks fat cells. Interlobular ducts can be observed in the dense interlobular connective tissue.

B. Lactating Mammary Gland

On slide #92, (examine even and odd) notice a tremendous increase in the number of lobules. Within the lobules, secretory alveoli are seen in varying functional states. In some places the secretory portions are filled with milk (wide lumen and thin lining cells) and in other areas they are not (lumen narrow and epithelial height is increased). Some of the epithelium appears vacuolated due to lipid extraction during histological preparation. Try to find the nuclei of a myoepithelial cell (within the basement membrane). Note the presence of plasma cells within the intralobular connective tissue and the decrease in interlobular connective tissue. How can you differentiate the lactating mammary gland from the thyroid gland?

C. Nipple

Slide #93 with reverse ocular examine the general topography of the nipple. Note the dark staining epidermal covering, dense connective tissue stroma, and the lactiferous ducts. Under low power observe the highly folded stratified squamous epithelium, dermal papillae and sebaceous glands. At higher magnification observe the pigmentation in the basal cells of the epithelium. Bundles of smooth muscle run in various planes in the stroma, and the lactiferous ducts can be seen as large, elongated spaces lined with one or two layers of columnar epithelium.