Respiratory epithelium is another name for ciliated pseudostratified columnar epithelium with goblet cells. "Pseudostratified" refers to the histological appearance in which the nuclei are not aligned in the same plane and is really an artifact of sectioning and the irregular shape of the cells. An important point is that all cells make contact with the basement membrane and are in fact a single layer of cells--hence the "pseudo." Goblet cells are so-called because of their distinctive appearance on histology; they secrete mucus which keeps the epithelium moist and traps particulate material moving through the airway. ... Goblet cells are glandular epithelial cells that are specifically designed to secrete mucus. ...
The cilia of the respiratory epithelium beat in a concerted effort to move mucus and trapped particles towards the oropharynx for expectoration or swallowing to the stomach where the acidic pH helps to neutralize any foreign material or micro-organisms. cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ... The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ...
Although the respiratory tract passes through and includes the oropharynx the swallowing of food exposes the epithelium to constant wear and tear. For this reason there is a transition zone superior to the larynx and caudal to the nasopharynx where the respiratory epithelium gives way to stratified squamous epithelium which is better suited to the constant sloughing and abrasion. The squamous layer of the oropharynx is continuous with the esophagus. In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration or breathing. ... The pharynx (plural pharynx), or voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. ... The squamous epithelium is epithelium consisting of one or more cell layers, the most superficial of which is composed of flat, scalelike or platelike cells. ... The esophagus (also spelled oesophagus/Åsophagus), or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. ...
Cilia in the epithelium of the olfactory region arise from olfactory cells.
Depending on the extent of abrasive forces on the epithelium, the pharynx is either lined with respiratoryepithelium (nasopharynx or epipharynx) or with a stratified squamous epithelium (oropharynx or meso- and hypopharynx), which also covers the surfaces of the oral cavity and the oesophagus.
The histological structure of the epithelium and the underlying connective tissue of the bronchi corresponds largely to that of the trachea and the main bronchi.
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