Mucous blanket

The ciliated epithelial cells extend down the respiratory tract to the respiratory bronchioles. The cilia provide locomotion for the overlying mucous blanket, propelling mucus and associated debris forward in the most anterior portion of the nares or propelling it to the oral cavity in the most posterior portion of the nasopharyngeal compartment. In the tracheobronchial compartment, mucus and associated material are moved upward to the oral cavity. 

The aqueous layer covering the walls of the airways is thought to consist of two phases, a less viscons sol phase, in which the cilia beat and, above, a more viscous gel phase, the mucous blanket (6,80 Fig. 7). The relatively low viscosity of the sol layer allows the cilia to beat freely. This blanket, containing trapped particles, is moved toward the pharynx by ciliary action. Its total thickness varies from 5-30 pm in the trachea (75) to less than 1 pm in the peripheral airways, and shows... 

There is general agreement that a surfactant film exists at the air-aqueous interface. It appears as a eontinuous amorphous or multilayered strueture (13,14,75). The sol and gel phases have also been reported to be separated by osmiophilic membranes that are thought to consist of surfactant and may act as a lubricant to facilitate sliding of the mucous blanket on the sol phase (6,85-... 

Figure 7 Diagram of mucous blanket of the conducting airways Although the exact structure of the mucous layer of the airways is unknown, the diagram shows some of the features that have been demonstrated in recent light and electron microscopic studies. An osmiophilic film is seen at the air-liquid interface, which has a multilaminated appearance and exists in various degrees of thickness (see inset). Beneath this surfactant film lies an aqueous hypophase, again of variable thickness, in which are found macrophages, mucus, and osmiophilic lamellar structures. CC, Clara cell CEP, ciliated epithelial cell GC, goblet cell.

The pharynx, larynx, trachea and bronchi are lined with pseudostratified, ciliated columnar epithelium that contain at least eight cell types, including mucous secretory goblet and Clara cells, which produce a protective mucus layer of 5-10 jum thickness (see Table 9.2). Subepithelial secretory glands, present in the bronchial submucosa, also contribute to the mucus blanket [9]. Through coordinated ciliary movement a propulsive wave is created, which continuously moves the mucus layer up towards the larynx. Consequently, the mucosal surface of trachea and bronchi is constantly swept to remove inhaled materials. As the bronchi divide into bronchioli, the ciliated columnar respiratory epithelium is much thinner and changes to a simpler non-ciliated cuboidal epithelium. The epithelium in the terminal and respiratory bronchioles consists of ciliated, cuboidal cells and a small number of Clara cells. However, Clara cells become the most predominant type in the most distal part of the respiratory bronchioles [10]. 

Hydrazoic acid is a volatile, endothermic liquid of unbearably acrid odor. Some of its properties are given in Table 18. Hydrazoic acid and its salts are very toxic. Inhalation of small quantities causes the blood pressure to drop and damages the mucous membranes. Exposure to HN3 vapors can be recognized by reddening of the eyes. Pure, liquid hydrazoic acid is very sensitive and explodes with slight mechanical stress. It is completely miscible with water and soluble in alcohols and ethers. Tests have shown that aqueous solutions with less than 20% hydrazoic acid do not detonate. Diethylether, which has almost the same boiling point (307.7 K) as HN3 can be used as a blanketing fluid. 

DOT CLASSIFICATION 6.1 Label Poison SAFETY PROFILE A poison. An irritant to skin, eyes, and mucous membranes. Questionable carcinogen with experimental neoplastigenic data. Flammable liquid when exposed to heat, flame, and oxidizers. Will react with water or steam to produce toxic and corrosive fumes. To fight fire, use water as a fire blanket. When heated to decomposition or on contact with acid or acid fumes, it emits highly toxic fumes of Br. See also BROMIDES. 

Flammable Liquid SAFETY PROFILE Poison by intraperitoneal route. Moderately toxic by ingestion. Mildly toxic by inhalation. Causes injury to liver and kidneys. An eye and mucous membrane irritant. Flammable liquid when exposed to heat, sparks, flame, or oxidizers. To fight fire, use alcohol foam, CO2, dry chemical water can blanket fire. Incompatible with Ca(OH)2, hydrocarbons, hydroxides, inorganic bases, KOH, NaOH, metal oxides, Explodes when heated. When... 

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