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THE RESPIRATORY SYSTEM Diane Hickson-Bick, PhD. Reading : Gartner and Hiatt, Chapter 12, p 235; Klein and McKenzie, pp199-210. Learning Objectives: Understand the differences between the conducting and respiratory portion of the respiratory system. Define the roles and composition of these two regions. Key Words : Conducting, respiratory, alveoli, cartilage, trachea, bronchus, bronchioles, vocal cords. The respiratory system The means by which, through a system of tubes, the body exchanges carbon dioxide for oxygen, which is then distributed throughout the body. 2 Parts: An upper conducting portion and a lower respiratory portion . A. CONDUCTING PORTION Consists of the extra-pulmonary nasal cavity, nasopharynx, larynx, trachea, bronchi and the intrapulmonary bronchi, bronchioles and terminal bronchioles. It serves two main roles: 1. To provide a conduit through which air can travel to and from the lungs 2. To condition the inspired air. Components of the Conducting System Cartilage (primarily hyaline) from C-shaped rings to irregular rings and small plaques. Prevents collapse of the walls. Collagen fibers Elastic Fibers : Tend to be oriented longitudinally in this area. Smooth muscle : From trachea to alveolar ducts. Contraction reduces diameter of tubes and restricts airflow Respiratory Epithelium Lines the conducting portions Ciliated, pseudostratified columnar epithelium Does not mediate gas exchange. Functions to cleanse, moisten and warm air before it enters the lungs. Numerous serous and mucous glands and a rich superficial vascular network in lamina propria. Goblet cells, producing a rich mucous secretion, abundant in the upper portions of the conducting tubes. The number of goblet cells, along with the amount of ciliated epithelium and cartilage, decrease as the conducting tubes gradually proceed into the respiratory portion. At the same time the content of smooth muscle and elastic fibers progressively increases. Ciliated pseudostratified columnar epithelium transitions to a simple columnar and finally a simple squamous epithelium in the alveoli. The rich goblet cell population tapers off in the smaller bronchi and these cells are absent from the terminal bronchioles. Ciliated cells continue beyond the goblet cells, preventing the accumulation of mucous. Cilia move fluid and mucus toward the oral cavity where it is swallowed or expectorated. Respiratory epithelium consists of 5 cell types: 1. Ciliated columnar cells; Most abundant, each having about 300 cilia on their apical surface. Many apical mitochondria provide energy for beating.
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2. Mucous goblet cells; Contain polysaccharide-rich mucous droplets. 3.
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This note was uploaded on 12/25/2010 for the course NEUROBIOLO MSI taught by Professor Rogerj.bick during the Spring '10 term at University of Texas Health Science Center at San Antonio.

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