Turbinate bone

Morpholine has also been tested for carcinogenicity by inhalation exposure in rats. Exposure to 10, 50, or 150 ppm 6 hours/day, 5 days/week, for up to 104 weeks was associated with dose-related increases in inflammation of the cornea, inflammation and squamous metaplasia of the turbinate epithelium, and necrosis of the turbinate bones in the nasal cavity, but no significant increase in the incidence of tumors. ... 

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 24-4 Cut-away view showing the lacrimal excretory system. Tears drain through the punctum (A) and eventually under the inferior turbinate bone of the nose. Dimensions of the canaliculi serve as references for probing and irrigation. B, canaliculus C, common canaliculus. (Redrawn with permission from Jones LT. Ophthalmic anatomy a manual with some clinical appHcations. 1. The orbital adnexa. Am Acad Ophthalmol 1970 70.)...

Turbinate Any of the scrolled spongy bones of the nasal passage. 

No deaths were observed in rats at concentrations up to 800 ppm or in mice up to 400 ppm in an NTP study lasting 13 weeks (6 hours/day, 5 days/week). Nasal cavity lesions and reduced body weight were seen in rats exposed at 800 ppm. In mice, renal tubular necrosis was found at 800 ppm, a dose that was lethal. Inflammation of the nasal turbinates was observed in female mice at 100 ppm and above and in male mice at 2 00 ppm and above. In an earlier study, slight growth retardation was observed in rats and mice exposed at 600 ppm for 13 weeks inflammatory and degenerative changes in the nasal mucosa were observed in both species. Myeloid hyperplasia in bone marrow occurred in male rats only. No effects were noted at 75 or 150ppm. 

C-formaldchyde in respiratory mucosa tissues were approximately 2-3 times that in olfactory mucosa tissues. Tlie H and C radioisotopes were chosen to distinguish between metabolic incorporation of oxidized fonnaldehyde metabolites ( C) and covalent binding ( H) into macromolecules. At all exposure concentrations, RNA was the most heavily C-labelcd macromolecule in the respiratory and olfactory mucosa. DNA from the respiratory and olfactory mucosa was C-labclcd at equivalent or greater levels than proteins. In the bone marrow, DNA was the most heavily " C-labeled macromolecule. DNA-protein cross links have also been identified in male rats and male Rhesus monkeys exposed to formaldehyde concentrations of 9.87 ppm for 6 hours. Concentrations of formaldehyde-protein cross links were greatest in the middle turbinate tissues and lowest in the nasophaiyngeal tissues, with some evidence of cross link formation seen in the larynx, trachea, carina, and major intrapulmonary airway tissues of two of the monkeys tested (Casanova et al. 1989a). 

The nose and throat showed no inflammation, swelling of the turbinates, or enlargement of the tonsils. The heart and lungs were normal. Hearing did not appear to be affected —the child responded to his name when it was whispered behind him. On structural examination, he was found to have C2 FS.Rii, T4FSlRl, an internally rotated temporal bone on the right, and external rotation of the left. There was mild condylar compression of the occiput. 

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