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Early Pregnancy Loss
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Lisa K. Perriera, Beatrice A. Chen, Aileen M. Gariepy
Anembryonic pregnancy: Previously described as “blighted ovum.” This is a gestational sac without a visible yolk sac and/or embryo (with no heart motion) in relationship to the mean sac diameter (MSD) size (Table 16.1). It occurs when the embryonic disk has failed to develop or has already been resorbed [4].
Fertilization and normal embryonic and early fetal development
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Asim Kurjak, Ritsuko K. Pooh, Aida Salihagic-Kadic, Iva Lausin, Lara Spalldi-Barisic
Along with the implantation process, changes occur in the embryoblast to produce a bilaminar embryonic disc, composed of the epiblast and the hypoblast. Early in the 2nd week, the amniotic cavity appears as a space lined with amnioblasts derived from the epiblast. By the end of the 2nd week, the embryonic disc becomes oval in shape. Along the median line in the posterior region of the embryonic disc, a thickening of the epiblast called the primitive streak appears, and it defines the longitudinal axis of the embryo. During the 3rd week, lateral epiblast cells migrate medially, enter the primitive streak, and then converge to form the primitive groove.
Embryology of the Spinal Cord, Peripheral Nerves, and Vertebrae
Published in Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand, Pediatric Regional Anesthesia, 2019
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand
In stage 6 (two weeks of gestation), the germ-disc is didermic and consists of two layers of cells, the entoderm (ventrally) and the ectoderm (dorsally) which together constitute the embryonic disc (Figure 1.1). The first rudiments of the axial skeleton are mesodermal cells, which can be recognized in stage 7 (0.5- to 1-mm embryos, 16 to 17 d). These cells appear dorsally and differentiate as the prechordal plate (Figure 1.2). In stage 8 (1- to 1.5-mm embryos, 17 to 19 d), the notochord and dorsal ectodermal structures differentiate. As they develop, they set up the neural plate rostral to both the primitive streak and Hensen’s node (Figure 1.3).9
A rare pseudo tumour in the extraembryonic coelom in first trimester of pregnancy: ultrasound and pathology
Published in Journal of Obstetrics and Gynaecology, 2019
Seiji Sumigama, Atsushi Enomoto, Satoshi Matsukawa, Takafumi Ushida, Kenji Imai, Tomoko Nakano, Tomomi Kotani, Fumitaka Kikkawa
In a review of normal early human development, there is a ‘primary yolk sac’ and ‘secondary yolk sac’ as embryological terms (Moore and Persaud 2011). At 4 weeks of gestation, there is an embryonic disc consisting of two-layered cells; embryonic epiblasts and hypoblasts. The primary yolk sac is formed from embryonic hypoblasts, and is lined with an exocoelomic (Heuser’s) membrane (cuboidal cells), outside of which is the extraembryonic mesoderm (spindle-shaped cells) (Moore and Persaud 2011; Sadler 2011). Several days later, additional cells are produced by the hypoblasts, migrate along the inside of primary yolk sac and form a new cavity, the secondary yolk sac (Sadler 2011). Until the end of 4 weeks, the primary yolk sac is pinched off and its residue is found in the extraembryonic coelom; however, it is rarely detected by ultrasonography. The ‘yolk sac’ usually detected by ultrasonography after 4 weeks is the ‘secondary yolk sac’ (Kurjak et al. 2008). In this case, the cystic mass was not observed at 4 weeks and was found at 5 weeks of gestation. The timing coincided with the formation of a residual primary yolk sac, and further, the pathological structure consistent with it. Thus, we speculated that the mass was a residual primary yolk sac that had become hyperplastic for some reason.
Application of amniotic membrane in reconstructive urology; the promising biomaterial worth further investigation
Published in Expert Opinion on Biological Therapy, 2019
Jan Adamowicz, Shane Van Breda, Dominik Tyloch, Marta Pokrywczynska, Tomasz Drewa
The mammalian embryo is enclosed in the fluid filed amniotic sac of the placenta, surrounded by the AM. In humans, 6–7 days after fertilization, AM starts to develop during blastocyst implantation in the endometrium [6]. Subsequently, the embryoblast (inner cell mass within the blastocyst) differentiates into a bilaminar disc composed of the hypoblast and epiblast. Eventually, amnioblasts derived from the epiblast invade the space between the trophoblast and the embryonic disc, migrating to the inner amniotic layer and gradually constitute the external lining of the amniotic cavity. The amniotic and chorionic fetal membranes separate the embryo from the endometrium. The amniochorionic membrane forms the outer limits of the sac that encloses the embryo, while the innermost layer of the sac is the AM [7].