Roles of tissues in the lungs

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  • Created by: Steff06
  • Created on: 11-04-16 12:17
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  • Roles of tissues in the lungs:
      • Plays a STRUCTURAL role. SUPPORTS trachea and bronchi, holding them open. Prevents collapse when air pressure inside is low during inhalation.
      • Cartilage does not form a complete ring in trachea so there is some FLEXIBILITY. Allows neck to be moved without constricting airways and allows the oesophagus to expand during swallowing.
      • Can contract. When it contracts, CONSTRICTS airway which makes LUMEN of airway NARROWER. Effect of smooth muscle is most obvious in BRONCHIOLES. Constricting lumen can RESTRICT FLOW of air to and from alveoli.
        • Controlling flow of air to the alveoli may be important if there are harmful substances in the air. Contraction of smooth muscle+control of airflow is not a voluntary act.
      • When smooth muscle CONTRACTS, it REDUCES DIAMETER of LUMEN of the airway. Smooth muscle cannot reverse this effect. When the airway constricts, it DEFORMS the ELASTIC FIBRES in the loose tissue.
      • As smooth muscle RELAXES, the elastic fibres RECOIL to their original size and shape which helps to DILATE the airway.
      • These secrete MUCUS. Role of mucus is to TRAP tiny particles from the air such as pollen and bacteria. Trapping the bacteria so they can be removed will REDUCE RISK of infection.
      • Epithelium consists of CILIATED CELLS. These cells have NUMEROUS tiny, hair-like structures projecting from their membrane. These are the CILIA.
      • Cilia move in a  synchronised pattern to waft the mucus up the airway to the back of the throat. Once there, mucus is swallowed and acidity in stomach will kill any bacteria.


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