Human nasal cavity

Nasal cavity. The nasal cavity has a volume of 15 to 20 cm3 and a surface area of 150 to 180 cm2.110 111 The human nasal cavity is divided into two halves by the midline septum.45 107 Each cavity consists of three regions (1) vestibules, which are the anterior sections of the nasal cavity, (2) respiratory region, consisting of turbinates or chonchae (superior, middle, and inferior), and (3) olfactory region, which constitutes about 10 percent of nasal area.45 107... 

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... 

Lysozyme (LZ) is an enzyme that is abundantly present in the mucosal membranes that line the human nasal cavity and tear ducts. It can also be found in high concentration in egg white. LZ destroys bacterial cell walls by hydrolyzing the polysaccharide component of the cell wall. Human milk contains 0.4 g/liter of LZ, an enzyme that contributes to antibacterial activity in human milk. 

Boecker BB, Hahn FF, Cuddihy RG, et al. 1983. Is the human nasal cavity at risk from inhaled radionuclides In Thompson RC, Mahaffey JA, ed. Life-span radiation effects studies in animals What can they tell us Proceedings of the twenty-second Hanford life science symposium held at Richland, Washington, September 27-29, 1983. Hanford Life Sciences Symposium 22nd. Springfield, VA United States Department of Energy, 564-577. 

Figure 1. Innervation of the lateral vail of the human nasal cavity (IS).

Schiller et al. (1986) analyzed factors affecting ultraline aerosol deposition in the human airway. Deposition of ultrafine particles in replicate cast models of the human nasal cavity is measured by Cohen et al. and Swift et among... 

Computer simulation studies of transport and deposition of ultrafine particles in human nasal cavities were reported by Yu et and Scherer et In these sim-... 

Hahn, I., Scherer P.W., and MozeU M.M. (1993). Velocity Profiles Measured for Airflow through A Large-Scale Model of the Human Nasal Cavity. J. Appl. Physiol., Vol. 75, pp. 2273-2287. 

Odors are perceived via the olfactory system, which is composed of two organs in the nose the olfactory epithelium, a very small area in the nasal system, and the trigeminal nerve endings, which are much more widely distributed in the nasal cavity (11). The olfactory epithelium is extremely sensitive, and humans often sniff to bring more odorant in contact with this area. The trigeminal nerves initiate protective reflexes, such as sneezing or interruption of irrhalation, with exposure to noxious odorants. 

These cues are important in rearing, territorial, courtship and, in particular, sexual behaviors. The vomeronasal organ (VNO) is separate from the main epithelium in mammals, comprising a thin epithelial tissue within a bony capsule in the lateral wall of the nasal cavity. It is probably vestigial in humans. The VNO epithelium contains at least two populations of microvillar chemosensory neurons one is in the more apical aspects of the epithelium, while the other lies in the more basal region. These two populations of vomeronasal neurons (VNs) are defined by the differential expression of several genes. For example, the apical VNs express the G-protein subunit Ga, while the basal neurons express Ga0. Apical and basal VNs also... 

One hurdle for proponents of human pheromones is the lack of clear evidence for a functional human vomeronasal organ (VNO). Located within the nasal cavity,... 

In humans and other mammals, the sense of smell begins when we inhale some odorant through our nose. The inhaled air enters the nasal cavity where it encounters a large number of olfactory neurons located in the nasal epithelium associated with bony structures located at the rear of this cavity. These bony structures are known as turbinates. In a human, these turbinates create a surface area of a few square inches. In a medium-size dog, in contrast, the turbinates have a surface area several times larger. It is small wonder that dogs have a more acute sense of smell than we do. 

Chronic exposure of rats to 1 or 12 ppm 6 hours/day, 5 days/week for 2 years caused an increased incidence of rhinitis, squamous metaplasia, and epidermal carcinomas of the nasal cavity. The lARC has determined that there is sufficient evidence for the carcinogenicity of PGE in animals and that it is possibly carcinogenic to humans. ... 

The lARC has noted, however, that thiram can react with nitrite under mildly acidic conditions, simulating those in the human stomach, to form N-nitrosodimethylamine, which is carcinogenic in a number of species." Dietary administration of 500 ppm thiram plus 2000ppm sodium nitrite for 2 years caused a high incidence of nasal cavity tumors in rats vs. no tumors in controls or in animals given only one compound. "... 

Respiratory Effects. No studies were located regarding respiratory effects in humans. The only data available indicating respiratory effects were reports of irritation of the nasal cavity in mice after acute (15 minutes) inhalation of vapors of hexachlorobutadiene at concentrations of 155 ppm or greater (de Ceaurriz et al. 1988). The importance of this finding to human health is uncertain. 

Acute-Duration Exposure. No data are available on the effects of hexachlorobutadiene in humans after acute exposure by inhalation, oral, and dermal routes. Hexachlorobutadiene (50 ppm) was lethal in mice after acute (5 days) inhalation exposure and caused irritation of the nasal cavities following 15 minute exposures to concentrations of 15 ppm or greater (de Ceaurriz et al. 1988 NIOSH 1981). Because sufficient data are not available to determine target organs or determine critical effect levels, an acute inhalation MRL cannot be determined. 

In humans, acute high-dose exposure leads to liver and kidney damage. In rodents, inhalation exposure causes primarily proliferative lesions in nasal cavities. After intra-gastric administration, liver and kidney were the main target organs. Some evidence of adverse effects on reproduction was observed both in humans and rodents. 

A -Vinyl-2-pyrrolidone metabolites and polyvinyl pyrrolidone are excreted mainly in urine. Inhalation of low concentrations of A -vinyl-2-pyrrolidone by rats can cause nasal cavity inflammation, atrophy of olfactory epithelium and hyperplasia of the basal cells of the respiratory and olfactory epithelium. In humans and experimental animals, polyvinyl pyrrolidone accumulates in vacuoles of cells of many organs and, in humans, may be accompanied by pulmonary fibrosis and pneumonia. There have been no genetic toxicity studies with either compound. 

---