Pulmonary Host Defence

Pulmonary Host Defence - Dr Sunil Sharma Senior Resident...

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Dr Sunil Sharma Senior Resident ept. of Pulmonary Medicine Dept. of Pulmonary Medicine
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ajor function of the respiratory system is to ` major function of the respiratory system is to procure O 2 & to eliminate CO 2 from the body t rates required by tissue metabolism at rates required by tissue metabolism mbient inspired air along with O ontains ` Ambient inspired air along with O 2 contains noxious gases and a multitude of particulates cluding viable microorganisms including viable microorganisms oxic substances in air are derived from ` Toxic substances in air are derived from many sources
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aturally occurring processes can give rise to ` naturally occurring processes can give rise to large amounts of aerosolized particles including resuspension of soil missions from volcanic activity emissions from volcanic activity forest fires, photochemical reactions etc. ` Airborne particles also include biologically derived viruses, bacteria, fungi, algae, spores, and pollens ` Industrial and occupational sources add SO 2 , O NO NH ydrocarbons & inorganic and CO,NO 2 , NH 4 ,O 3, hydrocarbons & inorganic and organic particles to the inspired air
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pper and lower airways represent the largest ` Upper and lower airways represent the largest epithelial surface exposed to the outside environment ` Size of alveolar surface is that of a tennis court ` To allow gas exchange foreign substances and microorganisms must be stopped and removed ithout inducing inflammation without inducing inflammation ` variety of defences exists to protect host from the harmful effect of microorganisms & air pollutants
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Airways and their mucosa ` Luminal defence mechanisms Anatomical barrier Cough ucociliary learance ` Blood derived cells of the mucosa Dendritic cells ymphocytes (T ells cd ;NK ells Mucociliary clearance Secretory IgA Lysozymes, lactoferrins Defensins pithelial cells Lymphocytes (T-cells; cd; NK cells) B lymphocytes Eosinophils; mast cells; basophils ` Epithelial cells Epithelial barrier Mucin release Antimicrobial peptides Alveolar spaces ` Pneumocyte types I and II Bacterial receptors Chemotactic factors Growth factors; cytokines ` Alveolar macrophages ` Lymphocytes ` Neutrophils G nd psonins ` IgG and opsonins ` Surfactant
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Anatomical barrier ` nose is efficient upper airway defence mechanism that removes most airborne particles and water- oluble gases from inspired air soluble gases from inspired air ` Air entrained through the nasopharynx is subject to ltration through tortuous epithelial passages filtration through tortuous epithelial passages ` foreign particles of 10 μ m effective diameter are efficiently removed & nasal hairs assist in trapping larger inhalants ` sneezing is an effective means of expelling some of airborne contaminants
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icrobes deposited into & attempting to colonize the ` Microbes deposited into & attempting to colonize the nasopharynx has to compete against a dense flora of nonpathogenic endogenous bacteria `
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This note was uploaded on 12/03/2011 for the course MEDICINE 350 taught by Professor Dr.aslam during the Winter '07 term at Medical College.

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Pulmonary Host Defence - Dr Sunil Sharma Senior Resident...

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