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The urinary and reproductive systems and the external genitalia
Published in Frank J. Dye, Human Life Before Birth, 2019
The ducts of both males and females arise from intermediate mesoderm, close to the splanchnic mesoderm from which the gonads arise. Two pairs of ducts arise side by side from the intermediate mesoderm: the mesonephric ducts and the müllerian ducts (see Figure 18.4A). The mesonephric ducts, as previously discussed, contribute to the formation of the mesonephros.
Formation of the Cranial Base and Craniofacial Joints
Published in D. Dixon Andrew, A.N. Hoyte David, Ronning Olli, Fundamentals of Craniofacial Growth, 2017
In the early part of the 3rd week of human development the third of the primary germ layers, cells of the intraembryonic mesoderm, begin to migrate in both lateral and cranial directions from the midline primitive streak, insinuating themselves between the ectodermal and endodermal layers of the embryonic disc. As the notochord and neural tube form in the midline axis of the embryo, the intraembryonic mesoderm that streams toward the head end of the disc thickens into two well-defined columns of paraxial mesoderm, one on either side of the notochord. More laterally, a thinner intermediate mesodermal band differentiates and beyond it, at the periphery of the embryonic disc, lies an even thinner lateral-plate mesoderm. These mesodermal aggregations are readily seen in cross-sections of the embryonic disc at the end of the 1st month of development. The intermediate mesoderm is significant for its role in the development of the urogenital system, while the cardiovascular and lymphatic systems, as well as the serous membranes that will line the major body cavities, are derivatives of lateral plate mesoderm.
Normal fetal development and growth
Published in Louise C Kenny, Jenny E Myers, Obstetrics, 2017
Each pronephric duct grows towards the tail of the embryo. As it does so it induces intermediate mesoderm in the thoracolumbar area to become epithelial tubules called mesonephric tubules. The pronephros degenerates while the mesonephric (Wolffian) duct extends towards the most caudal end of the embryo, ultimately attaching to the cloaca.
Immunohistochemical Panels to Evaluate Important Immunophenotypes of Human Mesonephros
Published in Fetal and Pediatric Pathology, 2023
Ping L. Zhang, Jacqueline K. Macknis
The main goals of our current study were to determine whether glomerular and tubular structures of mesonephros express similar protein markers to those in early metanephros. We selected the following key markers, known to be related to the development of metanephros, for evaluating the mesonephros in this study. PAX8 is involved in intermediate mesoderm transition and pronephric duct formation and is positive in parietal epithelial cells and at all levels of renal tubules [20,21]. GATA3 is another marker mainly involving in the development of the ureteric bud and its differentiation, and is also expressed in mesangial cells from the metanephric stromal progenitor cells [22,23]. AMACR was selected to confirm proximal tubules of mesonephros, as this marker is commonly used for identifying lesions associated with the proximal tubules [24]. In addition to routine hematoxylin and eosin staining, conventional PAS was utilized to detect the brush borders of proximal tubules and glomerular basement membranes (GBM) in mesonephros.
Premature ovarian insufficiency – the need for a genomic map
Published in Climacteric, 2021
During ovarian development, PGCs emerge in the wall of the yolk sac on day 18 as a small cluster of cells. Simultaneously, the genital ridges develop from the intermediate mesoderm. Between days 28 and 36, the PGCs migrate to the genital ridge. Subsequently, the oogonia undergo mitosis and increase up to 600,000 in number by 8 weeks. These oogonia then either continue multiplying through mitosis up until 28 weeks or continue down a path of meiosis for the generation of non-dividing PGCs, or undergo oogonial atresia. As a result, up to 7 million PGCs are present by the 20th week; however, after this time, atresia dominates, resulting in 1–2 million germ cells at the time of birth [62]. The majority of the primordial follicles will undergo atresia, occurring from birth through to the menopause. Therefore, inadequate in utero production of the PGC pool can result in POI [8,63].
Advances in understanding vertebrate nephrogenesis
Published in Tissue Barriers, 2020
Joseph M. Chambers, Rebecca A. Wingert
The urogenital system derives from the aforementioned intermediate mesoderm (IM), which is a narrow section of tissue situated between the paraxial and the lateral plate mesoderm. Early developmental studies are hampered by the limited number of molecular markers that label the emerging IM population. The first IM indicators to appear during embryogenesis are LIM-type homeobox (Lhx1) and the zinc-finger DNA-binding protein odd-skipped related (Osr1).4–7 The expression domains of these two factors intersect indicating the prospective IM and lateral plate mesoderm fields, as Osr1 is expressed across the entire length of the expanding somite tissue. Specific markers solely expressed in the IM do not turn on until about the 4–8 somite stage. The activation of Pax2 and Pax8 within a narrow band early in the IM is speculated to signify that the LPM and IM have assumed separate lineage trajectories. Complementary to these early expression pattern observations, functional assays in mice have demonstrated Lhx1, Osr1, Pax2, and Pax8 are all critical regulators of IM specification.4,6,8–10 For example, mice lacking either Lhx1 or Pax2/Pax8 fail to form the nephric duct, which is a pair of tubes required for assembly of the urinary system.7,11 Interestingly, experiments in chick embryos indicate that the competence to respond to these IM patterning factors is conferred by retinoic acid (RA) and Hox gene expression.12