Respiratory EpitheliumRespiratory Epithelium

By Group 5 Of Section 5By Group 5 Of Section 5

Respiratory EpitheliumRespiratory Epithelium Respiratory epitheliumRespiratory epithelium is is

a a type of epithelium found 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 epitheliumRespiratory epithelium lining the mouth, nose, throat, and trachea.

Respiratory EpitheliumRespiratory EpitheliumClassificationClassification: :

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. While all cells make contact with the basement membrane and 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.

Respiratory EpitheliumRespiratory EpitheliumClassificationClassification: :

The majority of cells composing the ciliated pseudostratified columnar epithelium are of three types:

a) ciliated cells. b) goblet cells. c) basal cells. The ciliated cells are 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.

Respiratory EpitheliumRespiratory EpitheliumClassificationClassification

The basal cells are 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 epithelium, which is better suited to the constant sloughing and abrasion. The squamous layer of the oropharynx is continuous with the esophagus.

Respiratory EpitheliumRespiratory EpitheliumMucociliary EscalatorMucociliary Escalator

The cilia of the respiratory epithelium beat in concert cranially, effectively moving secreted mucus containing trapped foreign particles toward the laryngopharynx, for either expectoration or swallowing to the stomach where the acidic pH helps to neutralize foreign material and micro-organisms. This system is collectively known as the mucociliary escalator and serves two functions: to keep the lower respiratory tract sterile, and to prevent mucus accumulation in the lungs.

Respiratory EpitheliumRespiratory EpitheliumMucociliary EscalatorMucociliary Escalator

The mucocilliary escalator The mucocilliary escalator is vital for the movement is vital for the movement of mucus up the of mucus up the respiratory tract to the respiratory tract to the pharynx. The mucus layer pharynx. The mucus layer is biphasic with a serous, is biphasic with a serous, sol layer in which the cilia sol layer in which the cilia beat and, above this, a beat and, above this, a viscoelastic or gel layer. viscoelastic or gel layer. Due to the viscous Due to the viscous properties of this upper properties of this upper mucous layer, the tips of mucous layer, the tips of the cilia catch in the layer, the cilia catch in the layer, which may contain which may contain particulate matter, and particulate matter, and drag it cranially toward the drag it cranially toward the laryngopharynx.laryngopharynx.

Respiratory EpitheliumRespiratory EpitheliumMucociliary EscalatorMucociliary Escalator

Respiratory EpitheliumRespiratory EpitheliumFunctionsFunctions

Clean the air inhaled by the body before it reaches the lungs. The respiratory lining is covered in mucus, which serves to capture pollutants as they travel through the respiratory cavities. Once captured, pollutants are swept back toward the outside of the body by small, hair-like structures called cilia. These cilia are constantly beating in a wave-like motion that moves foreign objects up and out of the body.

Respiratory EpitheliumRespiratory EpitheliumFunctionsFunctions

Warming air from the outside world before it reaches the lungs is another important function of the lining. The respiratory epithelium that lines nasal passages is particularly blood-rich. As air passes through the nose, warmth from the blood passing through the blood vessels underneath the lining is transferred to the air. The warmed air then continues its path toward the lungs, where it will supply the blood with oxygen.