BIOL 221 Lecture Notes - Lecture 7: Pseudostratified Columnar Epithelium, Exocrine Gland, Hyaline Cartilage
3 Mar 2020
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Document Summary
The trachea extends from the larynx in the cervical region to the level of the 5th thoracic vertebra. Mucus secreted by goblet cells in the ciliated pseudostratified columnar epithelium traps particles. The ciliary escalator moves particle-laden mucus up to throat where it can be spit out or swallowed. Constant irritation (e. g. , from smoking) causes the epithelium to change to stratified squamous epithelium without cilia or goblet cells. Seromucous glands located in the connective tissue of the submucosa secrete mucus through ducts. This mucus is also moved upward by the action of the cilia. Hyaline cartilage rings in the adventitia maintain the trachea as a patent opening. The trachealis muscle completes the adventitia posteriorly. This muscle tightens to regulate the amount of air entering the airways. Clearing the airways is essential to maintaining ventilation. This involves inhalation, followed by closure of glottis and forceful expiration.
