Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life.

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Distribution of collagen fibers in the aggregated lymphoid follicles of swine terminal ileum.

The arrangement of the collagen bundles was studied in the Peyer's patches of swine terminal ileum, by means of light microscopy (using silver-impregnation technique and picrosirius F3BA staining) and scanning electron microscopy (after NaOH-maceration). The lymphoid tissue forms a large and continuous patch along the antimesenteric border. The follicles are disposed mainly in the tela submucosa and sometimes they reached in the tunica mucosa surface (follicle/dome structures). Some follicles are located in the lamina propria of the tunica mucosa. Light microscopy showed black and brown-stained fibers, and yellow and red, and green-stained fibers, respectively by silver impregnation technique and picrosirius red staining, in the tela submucosa. In this tela, by scanning electron microscopy, the collagen fibers appeared as thick bundles forming a network of parallel layers. This network was denser in the interfollicular than in the follicular area, and formed a capsule surrounding the lymphoid follicles. Our results pointed out that a clear correspondence exists between the findings of currently used light microscopy techniques and the scanning electron microscopy after alkali-water maceration method. The arrangement of the collagen fibers in the antimesenteric border of the tela submucosa suggested a functional compartmentalization within the aggregated lymphoid follicles. This could facilitate the antigen-to-cell and cell-to-cell interaction during the immune response and thus create a suitable microenvironment for an active cell metabolism. The tunica mucosa showed a porous structure and its frequent gaps were likely the sites through which lymphocytes and other cells could freely migrate thus participating in the immunological activities of these structures.

Three-dimensional microanatomical dynamics of the ovary in postreproductive aged women.

OBJECTIVE: To evaluate the microanatomical dynamics of the ovary during postreproductive life. DESIGN: Retrospective, observational research study. SETTING: Institutional (university). PATIENT(S): Eleven (43- to 72-year-old) women in perimenopause, menopause, or postmenopause. INTERVENTION(S): Biopsies of ovaries obtained from patients undergoing gynecologic surgery or diagnostic procedures. MAIN OUTCOME MEASURE(S): Analysis of the 3-dimensional microanatomy of the ovary by transmission and high-resolution scanning electron microscopy. RESULT(S): The surface epithelium gets gradually flatter and is always present, even in advanced age. The surface appears smoother because of a smaller number of papillae and crypts as well as a decreased number and shortening of microvilli on surface epithelial cells. Signs of atrophy and fibrosis are evident. Primordial follicles are usually absent in postmenopause, whereas corpora atretica, hemorrhagica, and albicantia, scar tissue, and simple follicular cysts are common after menopause. Apoptotic and necrotic cells appear frequently within the surface epithelium. Major common features are a marked reduction in number and caliber of blood vessels with thickening of the vascular walls and changes in endothelial cells. CONCLUSION(S): Scanning electron microscopy studies are a useful complement to ordinary gynecologic diagnostic methods. Variations among patients of the same age range or functional status should be considered.

New advances in human embryology: morphofunctional relationship between the embryo and the yolk sac.

Organogenesis occurs during the first 8 weeks of human embryonic development; in consequence, early human growth and development take place before and in the absence of fully developed internal organs. During this period, normal development depends on several factors, but two are imperative: nutrition and a functional transport system for the distribution of nutrients and for waste disposal. The yolk sac (YS), a highly differentiated adnexal organ, is known to accomplish this fundamental task during early pregnancy. In this review, we summarize our contribution to the understanding of early human embryology, focusing interest on analysis of the morphofunctional link that is established between the human embryo and the YS during the embryonic period. Embryos were collected from the gestational sac after salpingectomies performed on patients with singleton pregnancies occurring in the fallopian tube. Samples of YS were taken from 20 human embryos at Carnegie stages ranging from 12 to 20. The age of the embryo was estimated from data of the patient's last menstrual history and confirmed from crown-rump length measurements and morphological characteristics of the specimen. The samples were fixed in 3% glutaraldehyde and then postfixed in 2% osmium tetroxide and prepared for light, transmission, and scanning electron microscopy according to conventional techniques. The samples were examined with a Philips 301 EM and an S-4000 Hitachi field emission SEM. The yolk stalk, and the YS wall with its corresponding endodermal, mesenchymal, and mesothelial layers, were analyzed. In accordance with their morphological features, the endodermal cells are equipped with organelles to fulfill several functions that are expressed in absorption from the vitelline cavity via microvilli present into the outer cell surface, in secretion to the extracellular space, and in the synthesis of numerous proteins which are transported by the bloodstream to the embryo. The mesothelial surface is provided with cell-surface differentiation that promotes a protective coat to prevent damage from compression or friction of the YS wall against the amnios, umbilical cord, and chorionic cavity wall during growth. The mesenchyme is the main site for blood vessel formation and gives rise to a network that provides the embryo with nutrients and a means of waste disposal. A critical analysis of the role of the endodermal vesicle in the production of fluid that is accumulated in the YS, and of the role that the vitelline duct play in the exchange function between the YS and intestinal tract, is presented. We have demonstrated that the vitelline duct is not functional after week 5 because of the closure of its lumen. This finding is discussed with reference to the biological meaning of the vitelline duct and its functional period of activity, and its possible role in the physiology of exchange during the embryonic period is assessed.