Anatomy and Embryology of the Mouth and Dentition
John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford in Head & Neck Surgery Plastic Surgery, 2018
In a 4-week-old embryo, the developing oral cavity (stomodeum) is present as a small, blind-ended pit bounded by five facial swellings (prominences) produced by proliferating zones of mesenchyme lying beneath the surface ectoderm. Much of the mesenchyme is derived from neural crest cells. The five facial swellings are the single frontonasal and the paired maxillary and mandibular processes (Figure 41.18). The centrally positioned frontonasal process lies above, the two maxillary processes are located at the sides and the two mandibular processes lie below the mouth. The maxillary and mandibular processes are derived from the first branchial arches. The facial processes are separated by grooves that, in the course of normal development, become flattened out by the proliferative and migratory activity of the underlying mesenchyme. Any disturbance in this process affecting, for example, the number, migration and subsequent differentiation (or apoptosis) and pattern formation of these cells can produce congenital abnormalities such as cleft lip and palate.
Clefts and craniofacial
Tor Wo Chiu in Stone’s Plastic Surgery Facts, 2018
The stomodeum is the cranial opening of the foregut (mouth and nasal apertures), and five swellings are formed ventrally: Paired mandibular swellings (from the first pharyngeal arch)Paired maxillary swellings (also from the first pharyngeal arch)Fronto-nasal prominence (downgrowth from primitive forebrain)
Summation of Basic Endocrine Data
George H. Gass, Harold M. Kaplan in Handbook of Endocrinology, 2020
The anterior lobe in the fetus forms from an ectodermal evagination of the stomodeum (primordial mouth) just anterior to the buccopharyngeal membrane (Rathke’s pouch). At the third fetal week, this grows toward the infundibulum, which is a downward extension of the diencephalon. At the close of the second month, Rathke’s pouch loses its connection with the mouth and comes into contact with the infundibulum. Cells in the pouch proliferate and form the anterior lobe of the pituitary gland. The pars intermedia develops from the posterior wall of Rathke’s pouch. The infundibulum produces the stalk and the pars nervosa.
Comparative toxicity of three differently shaped carbon nanomaterials on Daphnia magna: does a shape effect exist?
Published in Nanotoxicology, 2018
Renato Bacchetta, Nadia Santo, Irene Valenti, Daniela Maggioni, Mariangela Longhi, Paolo Tremolada
Figure 2 shows sagittal sections from both controls and exposed samples. D. magna gut is composed by a short anterior region, the stomodeum or foregut, which is protected by a thick chitin layer with the function of transferring food from the mouth to the actual gut. This one, called midgut has anteriorly two diverticula or hepatic ceca, and both have digestive and absorptive functions. The final portion of the gut is called hindgut and is involved in the reabsorption of liquids (Quaglia, Sabelli, and Villani 1976). Microscopic analyses were performed mainly focusing at the midgut region, that is specifically involved in absorption. Contrary to controls, samples exposed to CNMs displayed large masses occupying the entire lumen of the gut (Figure 2(D–L)). These masses entered into contact with the apical cell portions, and in the most affected fields. caused disruption of the peritrophic membranes, whose role in protecting epithelial cells from mechanical damages was thus overcome. While at low concentrations some gut regions seemed to be perfectly conserved, at the highest concentrations the final portion of the midgut appeared completely altered. In these cases the epithelium was extremely reduced, the brush border eroded, and cells showed large empty spaces among them and between them and the basal lamina. These morphologies were mainly diffused in the 50 mg L−1 groups for all the tested CNMs.
Iron nanoparticle bio-interactions evaluated in Xenopus laevis embryos, a model for studying the safety of ingested nanoparticles
Published in Nanotoxicology, 2020
Patrizia Bonfanti, Anita Colombo, Melissa Saibene, Luisa Fiandra, Ilaria Armenia, Federica Gamberoni, Rosalba Gornati, Giovanni Bernardini, Paride Mantecca
In previous papers, Xenopus laevis embryos have been effectively used as experimental model to screen the comparative toxicity of metal and metal oxide NPs (Bacchetta et al. 2012; Colombo et al. 2017). It has been demonstrated that different metal oxides, like CuO, ZnO and TiO2 are able to exert variable embryotoxic effects (Bacchetta et al. 2012; Nations et al. 2011) and that the model is able to predict the teratogenicity of NMs, as in the case of surface coated Ag NPs (Colombo et al. 2017). Remarkably, the main target organ for the NMs studied always resulted to be the intestine. It occurs only at developmental stages following the stomodeum opening, when embryos begin to swallow NP suspensions (Bonfanti et al. 2015). At that point, ZnO NPs come in contact with the intestinal epithelium, where they are adsorbed through different mechanisms, induce oxidative damages and consequent histological lesions to the intestinal mucosa (Bacchetta et al. 2014). Together, these evidences suggest that Xenopus embryos might be profitably adopted to study the absorption mechanism and possible toxicity in a developing system of orally available NMs, like iron NPs that are potentially relevant for environmental or biomedical purposes. Moreover, it should be considered that Xenopus embryos represent a valuable model to bridge in vitro and in vivo studies using mammals, with negligible ethical implications. To confirm this, a study by Webster and collaborators (Webster et al. 2016) showed that after exposure to a range of NPs, the phenotypic score of Xenopus embryos showed a strong correlation with in vitro cell tests and, in particular, magnetite cored NPs, negative for toxicity in vitro and Xenopus, were further confirmed as nontoxic in mice.
Related Knowledge Centers
- Foregut
- Mouth
- Embryo
- Brain
- Pituitary Gland
- Pericardium
- Flexure
- Buccopharyngeal Membrane
- Lip
- Tooth