Sonoembryology
Arianna D'Angelo, Nazar N. Amso in Ultrasound in Assisted Reproduction and Early Pregnancy, 2020
At the ninth gestational week, the CRL is about 22 to 29 mm [10], and the body of the embryo develops into an ellipsoid shape with a large head [26]. This gestational age marks the end of the embryonic stage (Carnegie stage 23) and the beginning of the fetal stage. The fetus assumes a more natural state compared to the extreme flexion of earlier gestation; hence, the crown becomes the endpoint of the fetal head, and the true CRL can be measured reliably [21]. The head starts to be clearly divided from the body by the neck [19,22]; thus, it becomes possible to obtain acceptable images of the embryonic profile (Figure 14.14).
Life, death and immortality
Julie Kent in Regenerating Bodies, 2012
It was facilitated by the medicalization of pregnancy loss (ibid.:51) and began at a time before embryos or fetuses acquired attributes of ‘persons’. The extent to which this might be considered a ‘collaborative effort’ is an issue to which I will return; most significantly, scientists created an ‘embryological origin story’ and an entity called ‘embryo’ (ibid.:7), or what Hopwood calls an ‘embryological view of life’, which in turn, Morgan suggests, contributed to the naturalization of ‘the embryo’ and normalization of collection practices. Embryos, then, are cultural products that emerged from these practices. Anthropological and historical study of embryo collecting provides important insights into how embryological knowledge was produced. The Carnegie ‘stages’ of human development were constructed from the meticulous study of dead embryos and fetuses obtained through various means. At the beginning of the twentieth century, first-generation embryo collectors such as Franklin Mall, anatomist and embryologist at Johns Hopkins University, relied on personal and professional contacts for the procurement of tissue. Then, in processing these ‘dead specimens’, he, and others at that time, such as the German embryologist Wilhelm His, thinly sliced them and placed them on slides, materializing the embryos, giving them body and form and creating wax, plaster and, later, plastic models (Hopwood 2000, 2005, Morgan 2006, 2009). The founders of the Carnegie collection collected hundreds of late-term fetuses, and the reputation of the collection has frequently relied on a separation of the messy corporeal work of dissecting dead fetuses, to create these sections and models, and their more recent transformation into highly valued and visualized ‘icons of life’, which can generate research grants and funding (Morgan 2004, 2009).
Growth of the Ear Capsule
D. Dixon Andrew, A.N. Hoyte David, Ronning Olli in Fundamentals of Craniofacial Growth, 2017
Figure 12.2 from Müller and O’Rahilly (1980) shows the basis cranii interna of the fully developed human chondrocranium at Carnegie stage 23 (27-32 mm CRL, 8 post-ovulatory weeks). Note that chondrification is well advanced by 8-9 weeks (Anson and Donaldson, 1973).
Immunohistochemical Panels to Evaluate Important Immunophenotypes of Human Mesonephros
Published in Fetal and Pediatric Pathology, 2023
Ping L. Zhang, Jacqueline K. Macknis
This retrospective study has been approved by the Institutional Research Board of Beaumont Health, Royal Oak, Michigan, USA. The five cases containing mesonephros were obtained from human embryos ranging from 6 to 10 weeks of gestation (as dated from last menstrual period) and were retrieved from missed abortion or ectopic pregnancy specimens collected over 10 years. The embryos’ crown-rump lengths were all appropriate for embryonal age in correlation with their gestational age (as dated by the last menstrual period or two weeks after embryonal age), based on the Carnegie stage [25–27]. 5 metanephric kidneys from the 10th to 36th weeks of gestation (from early metanephros to fetal kidney near the term) were identified from our surgical pathology and autopsy cases for comparison with the mesonephros specimens. All mesonephros and metanephros specimens were without significant autolysis. These sections of mesonephros and metanephros were immunohistochemically stained for several markers that were typically used to label glomerular and tubular structures of kidneys. The markers included a general renal tubular marker PAX8 [21], stem cell marker OCT3/4 [28], GATA3 for mesangial-like cells and distal tubules [23], AMACR for proximal tubules [24], and kidney injury molecule-1 (KIM-1) for proximal tubular injury [29]. Traditional growth factor marker mTOR and its downstream 70S6K [30], mesenchymal marker vimentin [31] and early kidney marker WT-1 [32] were also evaluated in the mesonephros and metanephros in order to compare the maturation of mesonephros with metanephros over different gestational periods.
Prevalence of buried probe in complex congenital nasolacrimal duct obstruction and evaluation of its success rate post ‘probing and irrigation’: a single-centre retrospective study
Published in Orbit, 2018
Nishi Gupta, Neeraj Chawla, Suma Ganesh, Sima Das, Nidhi Dhawan, Smriti Bansal, Poonam Singla
It is important to understand the embryonic basis of a buried probe. At Carnegie stage 19, the lacrimal lamina separates from the surface ectoderm and forms the lacrimal cord. The lacrimal cord appears as a compact, continuous cellular cord that follows an oblique caudo-ventral-medial trajectory towards the nasal cavity. The epithelium of the inferior and lateral portions of the nasal cavity thickens and forms the inferior meatal lamina. During embryonic development from the 10th week, various significant changes take place. First, a lumen appears in the excretory lacrimal system, such that we can now distinguish a true lacrimal duct. Second, the epithelium of the lacrimal canaliculi not only makes contact with the palpebral conjunctival epithelium, but also both epithelia form a continuous epithelial lamina. Third, the caudal extreme of the lacrimal duct and the inferior meatal lamina make contact and the latter begins to cavitate. During the 12th week of development, resorption of the inferior meatal lamina is clearly visible. Failure of this cavitation into the node at this juncture could be responsible for buried probe.10,12
Lacrimal drainage system involvement in Peters anomaly: clinical features and outcomes
Published in Orbit, 2021
Nandini Bothra, Abhimanyu Sharma, Mohammad Javed Ali
The embryology of the lacrimal system is such that the morphology of the lacrimal drainage system is well developed in the embryonic stage itself (9th week, 23rd Carnegie stage). The lateral portion of the lacrimal cord is differentiated into superior and inferior canaliculus proximally and lacrimal sac distally and the medial part of the cord continues caudally and lateral to the inferior meatal lamina. After the 10th week, the canalization of the lacrimal cord and development of the surrounding tissue occurs.10 Development of face and has maxillary region as also the lacrimal drainage system is related to the first and second branchial arches. Any disruption in this development can lead to abnormality in the development of the lacrimal system.11
Related Knowledge Centers
- Fetus
- Ovulation
- Polar Body
- Embryology
- Embryo
- Model Organism
- Developmental Biology
- Hamburger–Hamilton Stages
- Pregnancy
- Fertilisation