Nasal vestibule

In mart, an overlooked feature is the occurrence of mucoid-like plugs in the foetal nostrils (Schaeffer, 1910). The presence of this blockage can be confirmed by endoscopic inspection in utero these plugs seem likely to affect free amniotic flow, since they appear to be reinforced by a folded membranous gathering at the nasal vestibule (PI. 4B). A degree of restriction of fluid access to the VN aperture, which is immediately caudal to the nostril aperture, and is patent in foetal life, may be a protective feature (Jordan, 1972). The timing of the dissolution of these sealant devices prior to parturition is regrettably not known. 

Figure 9.1 Lateral wall of the nasal cavity. A nasal vestibule B inferior turbinate C middle turbinate D superior turbinate Hatched area the olfactory region...

The upper respiratory tract, particularly the nose, has a unique anatomy that performs normal physiologic functions as well as innate defense against inhaled toxicants. The nose extends from the nostrils to the pharynx. Inspired air enters the nose through the nostrils. The nasal cavity is divided longitudinally by a septum into two nasal compartments. In most mammalian species, each nasal cavity is divided into a dorsal, ventral, and middle (lateral) meatus by two turbinate bones, the nasoturbinate and maxilloturbinate. These turbinates project from the dorsolateral and ventrolateral wall of the cavity, respectively. In the posterior portion of the nose, the ethmoid recess contains the ethmoturbinate. The nasal cavity is lined by a vascular mucosa that consists of four distinct types of epithelia. In rodents, these epithelia are (1) the stratified squamous epithelium that lines the nasal vestibule and the floor of the ventral meatus in the anterior portion of the nose (2) the non-ciliated, pseudostratified, transitional epithelium that lies between the squamous epithelium and the respiratory epithelium and lines the lateral meatus (3) the ciliated respiratory epithelium that lines the remainder of the nasal cavity anterior and ventral to the olfactory epithelium and (4) the olfactory epithelium (neuroepithelium) that lines the dorsal meatus and ethmoturbinates in the caudal portion of the nose. The relative abundance and exact locations of these upper respiratory epithelium differ among mammalian species. 

FIGURE 1 Sagittal section of nasal cavity showing nasal vestibule (A), atrium (B), respiratory area and inferior turbinate (Cl), middle turbinate (C2) and superior turbinate (C3), olfactory region (D), and nasopharynx (E). (Reproduced from ref. 5 with permission of Pharmaceutical Press.)... 

The human nasal cavity, bearing a total surface area of about ISOcm and a total volume of about 15mL, is divided by a midline septum into two non-connected parts. As a cross-sectional view is schematically shown in Fig. lA, the nasal cavity consists of several major differentiated regions. " The nasal vestibule is situated just inside of the nostrils, with an area of about 0.6 cm. The epithelial cells in this region are stratified, squamous, and keratinized. The atrium located at the back of the vestibule is the narrowest region, and has stratified squamous cells anteriorly and pseudostrati-fied cells with microvilli posteriorly. The olfactory... 

Fig. 1 (A) Cross-sectional structure of the human nose. NV = nasal vestibule AT = atrium NP = nasopharynx IT = interior turbinate and orifice of the nasolacrimal duct MT = middle turbinate and orifices of frontal sinus, anterior ethmoidal sinuses, and maxillary sinus ST = superior turbinate and orifices of posterior ethmoidal sinuses hatched area, olfactory region. (B) Four major cell types in the nasal epithelium (a) non-ciliated columnar cell with microvilli (b) goblet cell with mucous granules and Golgi apparatus (c) basal cell and (d) ciliated columnar cell with many mitochondria in the apical part. (Reprinted from Ref. with permission from Elsevier.)...

Carcinogenic potential of ammonia by the inhalation route has not been assessed in humans or animals. One case report was found of a white male who developed epidermal carcinoma of the nasal septum 6 months after being badly burned by accidental contact with a refrigeration ammonia-oil mixture (Shimkin et al. 1954). If ammonia played a role in the development of this cancer, it was most likely due to dermal exposure, not inhalation, since the substance was oily. However, some of the ammonia was probably inhaled into the nasal vestibule and absorbed into nasal mucous. No other such reports were located, although other cases of inhalation exposure to ammonia from spills have been followed for more than 6 months after exposure. One of 10 adult male mice exposed to ammonia gas for 15 minutes/day 6 days/week for 8 weeks had mitotic figures with an intact basement membrane and a carcinoma in situ in one nostril and one mouse had an invasive adenocarcinoma of the nasal mucosa (Gaafar et al. 1992). 

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