epitheliumis a type of epitheliumfound lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the "mucociliary escalator".
Respiratory epithelium lining the upper (cranial) airways is classified as "ciliated pseudostratified columnar epithelium." This designation is due to the arrangement of the multiple cell types composing the respiratory epithelium which results in the cell nuclei ; hence, it appears as though several layers of cells are present.
The respiratory epithelium lining the upper (caudal) airways is classified as "ciliated pseudostratified columnar epithelium." This designation is due to the arrangement of the multiple cell types composing the respiratory epithelium. While all cells make contact with the
basement membraneand are, therefore, a single layer of cells, the nuclei are not aligned in the same plane. Hence, it appears as though several layers of cells are present and the epithelium is called "pseudostratified".
The majority of cells composing the "ciliated pseudostratified columnar epithelium" are of three types: a)
ciliated cells, b) goblet cells, and c) basal cells. The ciliated cellsare columnar epithelial cells with specialized ciliary modifications. Goblet cells, so named because they are shaped like a wine goblet, are columnar epithelial cells that contain membrane-bound mucous granules and secrete mucus which helps maintain epithelial moisture and traps particulate material and pathogens moving through the airway. The basal cellsare small, nearly cuboidal cells thought to have some ability to differentiate into other cells types found within the epithelium. For example, these basal cells respond to injury of the airway epithelium, migrating to cover a site denuded of differentiated epithelial cells, and subsequently differentiating to restore a healthy epithelial cell layer.
Certain parts of the
respiratory tract, such as the oropharynx, are also subject to the abrasive swallowing of food. To prevent the destruction of the respiratory epithelium in these areas it changes to stratified squamous epitheliumwhich is better suited to the constant sloughing and abrasion. The squamous layer of the oropharynx is continuous with the esophagus.
ciliaof the respiratory epithelium beat in concert cranially, effectively moving secreted mucuscontaining trapped foreign particles towards toward the oropharynx, for either expectorationor swallowing to the stomach where the acidic pH helps to neutralize foreign material and micro-organisms. This system is collecively known as the "mucociliary escalator" and serves two functions: to keep the lower respiratory tract sterile, and to prevent mucus accumulation in the lungs.
The "mucocilliary escalator" is vital for the movement of mucus up the respiratory tract to the pharynx. The mucus layer is biphasic with a serous, sol layer in which the cilia beat and, above this, a viscoelastic or gel layer. Due to the viscous properties of this upper mucous layer, the tips of the cilia catch in the layer, which may contain particulate matter, and drag it cranially toward the
Altiere and Thompson Inhalation aerosols Lung biology in health and disease: 94
Wikimedia Foundation. 2010.
Look at other dictionaries:
respiratory epithelium — the pseudostratified epithelium that lines all but the finer divisions of the respiratory tract … Medical dictionary
Epithelium — This article is about the epithelium as it relates to animal anatomy. For the fungal structure of the same name, see Pileipellis. Epithelium Code TH H2.00.02.0.00001 Epithelium is one of the four basic types of animal tissue, along with… … Wikipedia
Respiratory tract — In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration.The respiratory tract is divided into 3 segments: *Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or… … Wikipedia
epithelium — epithelial, adj. /ep euh thee lee euhm/, n., pl. epitheliums, epithelia / lee euh/. Biol. any animal tissue that covers a surface, or lines a cavity or the like, and that, in addition, performs any of various secretory, transporting, or… … Universalium
Epithelium — The outside layer of cells that covers all the free, open surfaces of the body including the skin, and mucous membranes that communicate with the outside of the body. By contrast the endothelium is the layer of cells lining the closed internal… … Medical dictionary
Respiratory bronchiole — Infobox Anatomy Name = PAGENAME Latin = bronchioli respiratorii GraySubject = 240 GrayPage = 1098 Caption = Diagram of the alveoli with both cross section and external view. Caption2 = Schematic longitudinal section of a primary lobule of the… … Wikipedia
Pseudostratified columnar epithelium — Transverse section of tracheal tissue. Note that image is incorrectly labeled ciliated stratified epithelium at upper right. Code TH … Wikipedia
Olfactory epithelium — Section of the olfactory mucous membrane. Plan of olfactory neurons … Wikipedia
Corneal epithelium — Vertical section of human cornea from near the margin. (Waldeyer.) Magnified. 1. Epithelium. 2. Anterior elastic lamina. 3. substantia propria. 4. Posterior elastic lamina. 5. Endothelium of the anterior chamber. a. Oblique fibers … Wikipedia
Simple columnar epithelium — Vertical section of a villus from the dog’s small intestine. X 80. (Simple columnar epithelium labeled at right, third from top.) … Wikipedia