Female Reproductive System (Ii)

FEMALE REPRODUCTIVE SYSTEM (II) Marylee M Kott, MD

Learning Objectives: As Female Reproductive System I but in addition  Identify the components of the ovary.  Learn the stages of developing follicles and the corresponding morphologic features.  Identify the major types of trophoblastic cells.  Identify the components of the placenta at its various developmental stages.  Identify the duct system and lobules of the breast.  Learn the changes affecting the breast in pregnancy and lactation. Key Words: amnion, anchoring villus, antrum, areolar, sebaceous gland, atretic follicle, cervical canal, cervix, chorionic plate, chorionic villi, ciliated cells of the oviduct, corona radiata, corpus albicans, corpus luteum, cortex of ovary, cumulus oophorus, cytotrophoblast, decidua basalis, decidual cells, endocervix, endometrial glands, endometrium, menstruating stage endometrium: proliferative stage endometrium: secretory stage, follicular cell, germinal epithelium, granulosa cell, granulosa lutein cells, interlobular ducts, intralobular (alveolar) ducts, lactiferous duct and sinus, mammary gland, maternal blood supply, medulla of ovary, membrane granulosa, myometrium, nipple, oocyte, ovary, oviduct, ampulla oviduct, fimbriae oviduct, infundibulum oviduct, isthmus, peg cells, placenta, plicae, primary follicle, primordial follicle, secondary follicle, secretory alveolus, stem villus, stratum basalis, stratum functionalis, syncytiotrophoblast, theca externa, theca folliculi, theca interna, theca lutein cells, uterus, vagina, zona pellucida

B. THE OVARY :  Anatomy; Pay attention to the emboldened facts; the rest is devo/anatomy for introduction)  Paired pelvic organs which lie on either side of the uterus close to the lateral pelvic wall  Lie behind the broad ligament and anterior to the rectum.  Attach along their anterior margin (or hilus) by a double fold of peritoneum, the mesovarium, to the posterior aspect of the broad ligament.  Attach at their medial pole to the ipsilateral uterine cornu by the ovarian (utero-ovarian) ligament.  Attach at the superior aspect of their lateral pole to the lateral pelvic wall by the infundibulo- pelvic or suspensory ligament.  Throughout infancy and childhood, the ovary enlarges, increases in weight 30-fold, and changes in shape.  Reaches the size, weight, and shape of the adult ovary, and lies within the true pelvis by the time of puberty.  Three ill-defined zones are discernible on the cut surface: an outer cortex, an inner medulla, and the hilus.  Follicular structures (cystic follicles, corpora lutea, corpora albicantia) are typically visible in the cortex and the medulla.

 Surface Epithelium:  Single, pseudostratified layer of modified mesothelial cells, varying from flat to cuboidal to columnar. They are separated from the underlying stroma by a distinct basement membrane.  Surface inclusion cysts arise from cortical invaginations of the surface epithelium that have lost their connection with the surface.  Stroma:  Stroma of the ovarian cortex and medulla are continuous and similar (boundary between these two zones is ill-defined and arbitrary).  Spindle-shaped cells with a scant cytoplasm, resembling fibroblasts, arranged in whorls or a storiform pattern.  Cells are separated by a dense reticulum network and various amounts of collagen, most abundant in the superficial cortex.  Although frequently referred to as the tunica albuginea, the superficial cortex lacks the dense collagenous, almost acellular appearance and sharp delineation of the tunica albuginea of the testis.  Some of the stromal cells may become luteinized, with a polygonal shape, containing abundant eosinophilic/clear cytoplasm with variable amounts of lipid. Found singly or in small nests, usually in the medulla.  The number increases during pregnancy and after menopause, secondary to elevated levels of circulating gonadotrophins.  Decidual cells may occur singly, as small nodules or confluent sheets within the stroma of the superficial cortex. They represent a response of the ovarian stromal cells to elevated levels of progesterone.  Primordial Follicles:  Approximately 400,000 primordial follicles are present at birth and fill the ovarian cortex.  After birth, their numbers decrease progressively through the process of atresia and folliculogenesis until they eventually disappear, marking the end of menopause.  They consist of a primary oocyte surrounded by a single layer of flattened, mitotically inactive, granulosa cells, resting on a thin basal lamina.  The large spherical nucleus of the oocyte has finely granular, uniformly dispersed chromatin and one or more dense nucleoli.  The oocyte is arrested in prophase of the first meiotic division at the time of birth, entering a resting period until follicular maturation prior to ovulation or degeneration of the oocyte during atresia.

Primordial follicles  Maturing Follicles- Folliculogenesis:  Maturation begins during the luteal phase (equivalent to the secretory phase of endometrium) of the preceding cycle and continues throughout the follicular phase.  During each cycle only one such follicle, the preovulatory or dominant follicle, achieves complete maturation, culminating in the release of the oocyte, i.e., ovulation.  The other follicles that have begun the maturational process undergo atresia at earlier stages of their development.  Folliculogenesis and atresia also occur prenatally, throughout childhood, and during pregnancy, although maturing follicles do not reach the preovulatory follicle stage during these periods.

 Primary follicle (Stage 2) - the surrounding layer of granulosa cells assume a cuboidal to columnar shape accompanied by enlargement of the oocyte; First morphologic evidence of follicular maturation.  Multi-lamellar primary (pre-antral follicle; stage 3) - mitotic activity in the granulosa cells results in their stratification producing three to five concentric layers around the oocyte).  At this stage an eosinophilic, homogenous, acellular layer, the zona pellucida, appears, encasing the oocyte. (Its formation is usually attributed to the granulosa cells, but the oocyte may also play a role).  The zona pellucida is rich in acid mucopolysaccharides and glycoproteins.  Pre-antral follicles measure approximately 50-400 micra in diameter, and as they increase in size, they migrate into the deeper cortex and medulla.  Simultaneously, the surrounding ovarian stromal cells become specialized into  Several layers of theca interna cells.  An outer, ill-defined layer of theca externa cells. 

Primary follicles (Stage 2 – Stage 3).

 Secondary - antral (vesicular follicle; stage 4) - Secretion of mucopolysaccharide-rich fluid by the granulosa cells results in their separation by fluid-filled clefts which eventually coalesce to form a single large cavity or antrum lined by several layers of granulosa cells. Concurrently the oocyte enlarges to its definitive size and assumes an eccentric position at one pole of the follicle.

Secondary follicle

 M ature or Graafian follicle (Stage 5) - the granulosa cells proliferate at this eccentric position to form the cumulus oophorus which contains the oocyte in its center and protrudes into the antrum.

Graafian follicle.

 Ovulation - follicle:  Normally only one or two mature follicles will continue to grow after reaching a diameter of 4 mm, a size at the onset of the follicular phase (proliferative phase of endometrium). Only one of them will become the preovulatory follicle.  Late in follicular growth, the oocyte with its surrounding zona pellucida and a single layer of radially oriented, columnar granulosa cells, the corona radiata, detach from the cumulus oophorus and float in the antral fluid.  The preovulatory follicle protrudes partially from the ovarian surface at a point that represents the eventual rupture point, the stigma.  The follicle then ruptures, possibly secondary to contraction of the perifollicular smooth muscle cells, liberating the follicular fluid and oocyte with its surrounding layers into the peritoneal cavity.  Following ovulation the stigma is occluded by a mass of coagulated follicular fluid, fibrin, blood, granulosa and connective tissue cells and is eventually converted to scar tissue.

 Ovulation – oocyte: The mitotic and meiotic consequences of ovulation are NOT on the histology exam.  The oocyte within the ovulatory follicle enters telophase of the first meiotic division shortly before ovulation and chromosomal reduction occurs by migration of one-half of the oocyte chromosomes into a portion of the oocyte cytoplasm, separating the cell as the first polar body. The first meiotic division which began in fetal life is now complete

 The oocyte is now called the secondary oocyte.  Immediately after expulsion of the first polar body, the secondary oocyte enters the second meiotic division, arresting at metaphase until fertilization occurs.

 Granulosa Layer:  The granulosa cells within the maturing and graafian follicles are polyhedral and their cytoplasm does not have lipid until the onset of luteinization (several hours prior to ovulation).  Cells typically surround small cavities called Call-Exner bodies, which have a distinctive appearance and represent one of the most specific features of granulosa cells, both normal and neoplastic.  They are delimited from the granulosa cells by a basal lamina containing a deeply eosinophilic filamentous material consisting of excess basal lamina.  This layer is avascular, and without a reticulum framework. Cells produce estradiol, progesterone and inhibin.

 Theca Layers differ from granulosa cells in that they differentiate continuously from stromal cells at the periphery of developing follicles the process beginning during fetal life and ending at the end of the menopause.  The thecal component of the antral follicle is characterized by two layers: o A well-developed theca interna (produces hormones). o A less well-defined theca externa (does not produce hormones).  Theca interna cells have a rich vascular plexus and produce estradiol and androstenedione.

 Corpus Luteum of Menstruation (CLM):  Produced by the collapsed ovulatory follicle following ovulation in the absence of fertilization (14th day of the typical 28-day menstrual cycle) and is a round, yellow structure with many contours and a cystic center filled with a gray, focally hemorrhagic coagulum when mature.  The luteinized granulosa cells of the mature CLM (granulosa-lutein cells) are large, polygonal cells with abundant pale eosinophilic cytoplasm containing lipid droplets.  Theca interna cells become luteinized and they are approximately half the size of the granulosa- lutein cells.  During the maturation of the CLM, capillaries originating from the theca interna layer penetrate the granulosa layer and reach the central cavity, and involution changes begin on the 8th or 9th day following ovulation. There is progressive fibrosis and shrinkage over a period of several months and eventual conversion to a corpus albica ns.

Corpus luteum. Corpus albicans.

 Corpus Luteum of Pregnancy (CLP) Is usually larger than CLM due to the presence of a central cystic cavity filled with fluid and coagulum of fibrin and blood. The first morphologic evidence within the corpus luteum that conception has occurred is the absence of the regressive changes that normally appear in CLM.  The granulosa-lutein cells enlarge and their cytoplasm becomes vacuolated.  Eosinophilic colloid or hyaline droplets within the granulosa cells of CLP are almost diagnostic of pregnancy and become more numerous as gestation progresses, although by term their numbers decrease as they undergo calcification.  During puerperium (return to normal uterus state), the CLP undergoes involution and conversion to a corpus albicans in a similar fashion to that seen with CLM.

 Atretic Follicles:  Approximately 400 of the original 400,000 primordial follicles present at birth mature to the point of ovulation. The remaining 99.9% undergo atresia, a process that begins before birth and continues throughout reproductive life. Is most intense after birth, during puberty, and during pregnancy. . Factors which initiate atresia and determine which follicles will ultimately undergo atresia are unknown. Atretic process varies with the stage of follicular maturation that has been reached. Atresia of early follicles begins with degeneration of the oocyte then the granulosa layer. Follicles disappear without a trace. . Atresia of follicles that have reached the antral stage of development is more complex and variable and the earliest evidence of atresia is mitotic inactivity of the granulosa cells and a decrease in their number. . Thinning and focal exfoliation of the granulosa layer ultimately leads to obliterative atresia and the formation of a scar, the corpus fibrosum (or corpus atreticum). Some of the follicles may persist for an indefinite period of time at this stage as atretic cystic follicles.

 Hilus Cells: . Morphologically identical to testicular Leydig cells (except for a female chromatin pattern). . They may ensheathe nerve bundles and do ie as nests within loose connective tissue. Produce androstenedione. . Contain specific crystals of Reinke, which are homogenous, eosinophilic non-refractile, rod- shaped structures, with blunt, but occasionally tapered end.

 Rete Ovarii: . Ovarian analogue to the rete testis, it is a remnant of the mesonephric (Wolffian) duct which is present in the hilus of all ovaries. It consists of a network of irregular clefts, tubules and small cysts lined by epithelium that varies from flat to cuboidal to columnar.

THE PLACENTA: MUCH OF THE FOLLOWING YOU WILL GET IN DEVO, SO IT WILL NOT BE PART OF THE HISTOLOGY EXAM. THOSE PORTIONS ARE HERE TO ENLIGHTEN YOU AS TO THE PROCESS THAT OCCURS AND SO ARE IN RED. READ BUT DON’T STUDY FOR EXAMS

However, follicle development you do have to know, primordial through to graafian, as well as villus development and recognition of synciotrophoblasts, cytotrophoblasts, villus stage by tissue content, decidual and leutin cells because, they are component cells.

Development:  The placenta undergoes a series of profound morphologic changes during its short life span. It is of fetal origin except for a small amount of decidua adherent to the fetal membranes and the basal plate. Fully developed measures approximately 18 x 16 x 2.3 cm and weighs 400-600 grams and at the time of birth it occupies almost one third of the internal surface of the expanded uterus.  Fertilization of the ovum precedes implantation and development of the placenta.  The ovum is fertilized in the ampullar-isthmic junction of the fallopian tube and takes about 4 days to reach the uterus. By this time several cell divisions have occurred and a compact clump of cells, the morula, surrounded by the zona pellucida is formed.  A cavity appears in this solid mass of cells, after which it is called a blastocyst, a thin-walled, consisting of a single layer of cells, the trophoblast. There is an aggregation of cells called the inner cell mass, which bulges inward from the wall of the blastocyst into its cavity and gives rise to the embryo. It remains free in the uterine cavity for only 2 or 3 days after which it becomes implanted in the endometrium. The site of implantation may be anywhere on the wall of the uterus, most commonly it is high up on the posterior wall. Implantation usually begins about the seventh day after fertilization and is complete about the tenth day.

 Trophoblast cells Differentiate into two distinct cell layers;  Uniform Inner layer of cytotrophoblast cells with clear cytoplasm, distinct cell membranes, and vesicular nuclei.  Outer layer of syncytiotrophoblast, Multinucleated cells with dense nuclei suspended in abundant amphophilic (stains with both acidic and basic stains) cytoplasm.  Between these two layers are large mononuclear cells designated intermediate trophoblast with abundant amphophilic cytoplasm, sometimes more than one nucleus.  They emanate from the cytotrophoblast and display a gradient of increasing size proportional to their distance from the cytotrophoblastic stem cells. They fuse, particularly at the advancing margin, to form the syncytiotrophoblast.  Between the 9th and 13th post-fertilization days, blood-filled lacunae form within the rapidly growing trophoblastic mass and separate it into trabecular columns. As the lacunae enlarge, extensions of trophoblast left between them are called primary or trophoblastic stem villa. By day 15 the different germ layers are forming in the embryo and mesoderm has grown out from the developing embryo to form a lining for the shell of the trophoblast that surrounds the blastocyst. At this point the trophoblast is called the chorion. Mesoderm then extends into the villi to provide them with a mesodermal core. When this happens, the villi are called secondary villi. These grow and branch. Fetal blood vessels develop in the mesoderm in their cores and later become connected to the fetal circulation. The villus is now known as the tertiary stem villus.

Placental Hormones; Three main hormones produced human chorionic gonadotropin (hCG), Human placental lactogen (hPL), Pregnancy-specific beta 1-glycoprotein (SP1). The intermediate trophoblast contains a considerable amount of both hPL and SP 1 throughout pregnancy as well as small amount of hCG early in gestation. None of these hormones is localized in the cytotrophoblast. The Decidua is everything but the deepest layer of endometrium which is destined to be shed when a baby is born and lies between the chorionic sac and the basal layer of the endometrium is called the decidua basalis. The decidua basalis becomes the maternal part of the placenta, The only part that is of maternal origin. The endometrium that lies between the chorionic sac and the myometrium is called the basal plate and consists of decidua basalis plus the basal layer of the endometrium. The decidua parietalis lines the entire pregnant uterus except where the placenta is forming. The decidua capsularis is the portion of endometrium superficial to the developing embryo. Has to cover a larger and larger area and becomes very thin and atrophic as the embryo grows. After 3-4 months the size of the chorionic sac that contains the embryo has become so large that decidua capsularis comes in contact with the decidua parietalis at the opposite surface of the uterus; hence the uterine cavity is obliterated. The decidua capsularis then blends with the decidua parietalis and disappears as a separate layer.

Immature first trimester villi – KNOW THIS; Covered by two distinct layers of trophoblast, Inner layer of cytotrophoblast, Outer layer of syncytiotrophoblast.  Stroma is very loose and mucoid in appearance.  Hofbauer cells, the fetal tissue macrophages of the placenta, are numerous.  Vessels are small.

Second trimester villi  The syncytiotrophoblastic layer is thinner; The nuclei are less evenly dispersed.  The cytotrophoblast does not form a continuous layer and is difficult to find after 16 weeks.  The villous stroma is more compact and contains collagen.  Hofbauer cells are less conspicuous.  Villous capillaries are larger and more numerous.

Mature villi  Smaller still, and the syncytiotrophoblastic nuclei are irregularly aggregated to form syncytial knots which are found in about 30% of mature terminal villi.  The stroma is reduced to thin strands compressed between the numerous dilated capillaries, which constitute almost the entire surface of such villi.  The intervillous space develops rapidly to become an enormous blood sinus…  Bounded on one side by the chorion (chorionic plate) and on the other side by the deciduas basalis, it is filled with maternal blood, though fibrin deposits are also present.  Septa appear in the placenta at about 3 months and are composed of irregular folds of the decidua basalis that are drawn into the intervillous space by the relatively slowly growing anchoring villi. The cell islands that occur in the septa-folds are intermediate trophoblasts.

MEMBRANES: Amnion is the innermost aspect of the embryonic cavity. By 12 weeks the amniotic cavity completely occupies the chorionic sac. The cavity remains filled with amniotic fluid, which by the end of gestation amount to approximately one liter and is lined by a single layer of flat to cuboidal epithelial cells that reside on a basement membrane. The basement membrane is attached to an underlying thin layer of connective tissue. Although the amnion is adjacent to the chorion, is not truly fused to it, and is avascular. The chorion forms the base for peripherally radiating villi and to encapsulate the early embryo and developing amnion and is composed of a connective tissue membrane that carries the fetal vasculature, with Its inner aspect is bounded by the outer layer of amnion and its outer aspect is directly associated with the trophoblastic villi that sprout from the surface. THE UMBILICAL CORD: Surface is lined by a single layer of amniotic epithelium, Squamous to cuboidal which often becomes stratified and closely resembles its epidermal contiguity in the region of fetal cord insertion.  Parenchyma is composed of Wharton's jelly, made up mostly of mucopolysaccharides, and is derived from the extra-embryonic mesoblast and contains evenly distributed spindle-shaped fibroblasts with long extensions and numerous mast cells.  Two arteries and one vein are present in the normal umbilical cord embedded in the Wharton's jelly, the arteries spiralling in parallel around the vein. The arteries possess no internal elastic lamina and have a double-layered muscular wall composed of interlacing smooth muscle bundles while he umbilical vein has an elastic subintimal layer. Compared to the arteries, the vein has a larger diameter and a thinner muscular coat consisting of a single layer of circular smooth muscle.  Fetuses beyond 20 weeks of gestation have a vasa vasorum in the intra-abdominal portions of their umbilical arteries. The umbilical vessels divide within the chorionic plate , then dive beneath this layer to establish the circulation of primary vascular ramification and end in the terminal villi.  Using histologic criteria it is different to distinguish between the branches of the umbilical vein and umbilical arteries, while the e gross anatomic distribution is very distinctive.  Arteries always cross over veins when observed on the fetal surface of the placenta.

THE BREAST  Mammary glands are modified sweat glands with the specialized function of providing nutrients for the newborn infant. They also serve as target organs for a variety of hormones. Hormones that actively influence breast physiology are prolactin, estrogen and progesterone.  Estrogen promotes the growth and development of the duct system, Progesterone stimulates lobular development. The presence of prolactin is necessary for estrogen and progesterone to exert their effect.  The milk-producing lobular units are the functional components of the mature breast. A system of branching ducts connect them with the nipple-areolar complex, and they are surrounded by variable amounts of fat and connective tissue which make up most of the bulk of the breast.  Cooper's ligaments - Dense connective tissue which extends from the underlying pectoralis fascia to the skin of the breast, old the breast upward. Their lengthening is responsible for drooping of the breast with advanced age.

 Nipple and areola:  The tip of the nipple usually possesses 15-20 orifices (galactophores), which lead into the collecting ducts which deliver the milk to the exterior.  Are covered by a keratinizing stratified squamous epithelium.  Contain sebaceous and sweat glands.  Hair follicles are found only in the periphery of the areola.  The areolar surface is punctated by rounded elevations known as the tubercles of Montgomery. Contain the openings of the ducts of large sebaceous glands known as the glands of Montgomery.  Connective tissues ridged with bundles of smooth muscle and elastic tissue lie deep to the dermis in the nipple and areola. Most of the smooth muscle bundles seem to converge towards the region of the nipple.

 Duct System is arranged in a segmental, roughly radial pattern.  Different regions of the breast, both directly deep to the nipple and extending outward from the nipple, are drained by their own collecting system whose duct opens at the nipple. This arrangement divides the breast into poorly defined segments or lobes, which overlap and have no macroscopic or anatomic delineation.  Just deep to the nipple a collecting duct widens for a distance, defining an area termed the lactiferous sinus . The ducts, and particularly the sinuses, have longitudinal ridges which appear as prominent infoldings on cross-section.

 Stratified squamous epithelium extends a short distance into the openings of the major ducts, and transition to the columnar or cuboidal epithelium which characterizes the entire duct system occurs abruptly.  A continuous layer of luminal epithelial cells with oval nuclei perpendicular to the surface lines the lactiferous ducts. A discontinuous layer of myoepithelial cells exists between the basement membrane and the luminal epithelial cells. The long axis of the epithelial cell is perpendicular to that of the myoepithelial cell.  Ducts are surrounded by a loose fibrous tissue with a capillary network richer than that seen in the surrounding connective tissue and fat beyond this area.

 Glandular Area: The acini (alveoli) - a cluster of blind-ending glandular spaces which are the milk-producing units of the breast. They are entered by the terminal element of the ductal system (terminal ducts), set within a rich and specialized stroma which defines the lobular unit.  The Connective tissue:  Is usually loose; Possesses many capillaries.  Often contains lymphocytes, histiocytes, plasma cells and mast cells.  Is sharply demarcated from the surrounding fat and from the more dense fibrous tissue of the structural rather than functional portion of the breast.  The rounded acini have a luminal epithelium which is either cuboidal or columnar.  The cells of different lobular units vary greatly in their cytoplasmic features, but the cells within an individual lobular unit are usually similar to one another.  Beneath the luminal epithelium is a discontinuous layer of myoepithelial cells which tend to have smaller nuclei and clearer cytoplasm when compared to the luminal cells.  A basement membrane surrounds each acinus.

FEMALE REPRODUCTIVE SYSTEM II LABORATORY SLIDE 80, FALLOPIAN TUBE: Some slides may have two lumens in one section due to the tortuous course of some portions of the oviduct. The mucosal layer lies directly on the muscularis. It is composed of luminal epithelial cells and scanty lamina propria. The lining is simple columnar. Many of the lining cells have prominent cilia. A few slender and darkly stained intercalary, or peg cells are present among the other cells. A few lymphocytes may be present within the lining. The muscularis is composed of smooth muscle fibers that are poorly organized into outer longitudinal and inner circular layers. The serosa has a smooth flat mesothelial lining. Some slides may contain a few cystically dilated structures beneath the serosa called Walthard rests, which are lined by a transitional-type epithelium, often attenuated.

, OVARY: The ovary has 3 ill-defined zones, an outer cortex, an inner medulla, and the hilum. All slides have an ovary with a cortex and medulla, and some sections may contain a hilum having numerous blood vessels and rete ovarii. The surface epithelium is a single layer of flat to cuboidal to columnar cells (modified mesothelial cells. Focally in some sections the surface epithelium may invaginate into the underlying cortex and form glandular inclusions. Just beneath the surface epithelium is a palely stained layer, the tunica albuginea (the superficial portion of the cortex), composed of stromal cells and collagen fibers. Deeper, the stroma of the ovarian cortex and the medulla are continuous and similar and he boundary between cortex and medulla is ill-defined. Stromal cells are spindle-shaped and the nuclei stain darkly and have very little cytoplasm. Numerous primordial follicles are present in the superficial cortex, and are composed of a primary oocyte surrounded by a single layer of flattened, granulosa cells on a thin basal lamina. Secondary or pre-antral follicles may be present, consisting of an oocyte surrounded by 3-5 concentric layers of granulosa cells. Five to nine cystic structures are present in the cortex-medulla, representing various stages of the antral follicle, most of which are atretic cystic follicles. The atresia is manifested by a decrease in number of granulosa cells, and thinning and focal exfoliation of the granulosa layer. Some of the antral follicles contain fluid (follicular liquor), stained pink. The largest antrum is in the Graafian follicle that may be present in your slide. The Graafian follicle contains the oocyte surrounded by the zona pellucida, corona radiata (a single layer of radially oriented columnar granulosa cells) and the cumulus oophorus (a heaped-up area of granulosa cells containing the oocyte). Many corpora albicancia (white-pink hyalinized areas in the deep cortex or medulla containing a few hemosiderin-laden macrophages. These are the end result of the corpus luteum) and some corpora fibrosa (small, pink fibrous ribbon-like deposits in the deep cortex and medulla which are the end stage of the atretic follicles) are also present.

, OVARY (Pregnancy); Most of the slides contain a cortex, a medulla, and a hilus. All the structures described in the previous slide are present in #82. Many slides may contain a corpus luteum of pregnancy which is a well-delineated nodule composed of large polygonal cells (luteinized granulosa cells) with eosinophilic and slightly vacuolated cytoplasm. Eosinophilic colloid or hyaline droplets are present in some cells. A very rich capillary network runs among the cells and a thin layer of theca interna cells surrounds and invaginates the corpus luteum. The theca-lutein cells are much smaller than the granulosa-lutein cells. The hilus contains prominent blood vessels, and the rete ovarii is present in some sections, and consists of irregular clefts and tubules lined by a single layer of columnar to cuboidal epithelium surrounded by thin stroma.

, PLACENTA; Sections are from a 3rd trimester mature placenta and consists of the fetal membranes (amnion and chorion), villi, intervillous space and the decidual basalis. The amnion is lined by a single layer of flat to cuboidal epithelial cells covering a thin layer of connective tissue and is avascular. The amnion in your slide may be artifactually detached from the underlying chorion. The Chorion is composed of a connective tissue membrane containing the branches of umbilical vessels and is lined on the outer aspect (the side facing the villi and the intervillous space) by trophoblastic cells (mostly syncytiotrophoblastic cells). Most of the villi are small and have a fibrovascular core covered with a stretched layer of syncytiotrophoblastic cells. Some of the syncytiotrophoblastic cells cluster to form syncytial knots and some of the small terminal villi can be seen branching from the larger villi. The intervillous space contains maternal blood and clumps of fibrin. The decidua basalis is the maternal part of the placenta, composed of plump endometrial stromal (decidual) cells and large vascular spaces. Irregular folds (septa) of the decidual basalis can be seen in the intervillous space. They contain many groups of slightly large cells; each usually has one nucleus and abundant amphophilic cytoplasm. These are the intermediate trophoblastic cells. A single layer of amniotic flat to cuboidal epithelium covers the surface with, maybe, a few islands of stratified squamous.

, UMBILICAL CORD; The parenchyma of the cord is composed of loose, myxoid connective tissue (Wharton’s jelly) containing some fibroblasts. Two arteries and one vein are present. The arteries have no internal elastic lamina and a double-layered muscular wall of interlacing smooth muscle bundles. The vein has a single layer of circular smooth muscle.

, NIPPLE; The nipple and the surrounding areola are lined by a keratinized stratified squamous epithelium. Sebaceous glands in the dermis open on to the surface. The dermis contains apocrine and eccrine sweat glands and bundles of smooth muscle. In most slides the lactiferous ducts are cut in cross sections and have prominent infoldings lined by an inner cuboidal layer of epithelial cells and an outer layer of myoepithelial cells. Deeper in the tissue there are lobules in the resting stage containing terminal ducts and acini. Their lining is similar to that of the lactiferous ducts and lobules contain loose connective tissue.

, BREAST WITH PREGNANCY/LACTATION-ASSOCIATED CHANGES; Compare to slide #51. Lobules are tightly packed with expanded acini. Many cells of the inner epithelial layer, as well as the terminal ducts, have vacuolated cytoplasm and myoepithelial layer can be seen. The lumens of some acini and ducts contain eosinophilic secretions as well as neutrophils. Segmental ducts can be seen between lobules, which branch to give rise to terminal ducts. Each terminal duct enters a lobule and within the lobules it is an intra-lobular terminal duct. The segmental ducts, terminal ducts, and acini have similar linings, however, the segmental ducts usually do not show secretory changes.