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14 Cards in this Set
- Front
- Back
facts
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- airways and alveoli present a large area for gas exchange
- respiration continuously exposed airways to potentially harmful substances - variety of defense mechanisms |
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potentially hazardous substances
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1. solid particles: various sizes, dust, food, smoke
2. aerosols: fluid particles in air, oil-air 3. gases: ammonia, oxides of nitrogen, fuel fumes 4. biological agents: pollen, spores 5. infectious agents: bacteria, viruses, fungi |
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mechanism of particle deposition
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- location of deposition depends on particle size
- >5microm: bends of larger airways - 1-5 microm: sedimentation onto the walls of smaller airways - <1microm: peripheral airways, diffusion to surface or exhaled again |
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excretion of solid particles
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1. mucociliar escalator: particles entrapped in the mucous layer on top of the ciliated epithelium transported to the pharynx and swallowed
2. more hazardous, irritating mucous: cleared by coughing 3. injured epithelia become hyper-responsive: eg viral infection--> damage of epithelium --> coughing |
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macrophages
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- first line of defense
- 85% cells in liquid layer lining the alveoli are macrophages - phagocytize particles and microorganisms - complement, osponins and lysozyme contribute to the destruction of microorganisms - messengers to lymphoid tissues: critical role in immune system activation |
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large particles
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- eg soot, cigarette smoke
- too large for mucociliar escalator - moved into interstitium and deposited - chronic exposure: destruction and reduced fx of mucociliar epithelium which contributes to inability to remove these agents |
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very large particles
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- inspired food
- too big for transport to the pharynx - enveloped by CT and remain |
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deposition of toxic gases and aerosols
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determined by [] and solubility:
1. highly soluble gases in low []: SO2, entrapped in upper airways (nose, pharynx) 2. less soluble gases or higher concentrated gases: penetrate deeper into lungs, may reach alveoli |
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toxic gasses: protective mechanisms
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1. bronchospasm
2. mucous hypersecretion 3. cough 4. sneeze |
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metabolic fx of capillary bed
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- all blood returning from systemic circulation flows through lung
- large surface area - ideal place for cleansing blood of agents produced or released by other body tissues |
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vasoactive substances
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1. serotonin: cleared almost totally
2. NorEpi: cleared to some degree 3. bradykinin: inactivated by angiotensin-converting enzyme 4. angiotensin I: converted to a II 5. prostaglandins: majority degraded in lung |
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ACH, Epi and histamine
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not removed
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leukotrienes
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degraded by neutrophils
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exogenous toxic substances
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removed from blood
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