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Non respiratory functions of respiratory system

Non respiratory functions of respiratory system. Lung defence mechanism Functions of pulmonary circulation Metabolic and endocrine functions. Functions of respiratory passage Humidify and cool or warm the inspired air. Bronchial secretions contain secretory immunoglobulin(IgA).

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Non respiratory functions of respiratory system

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  1. Non respiratory functions of respiratory system • Lung defence mechanism • Functions of pulmonary circulation • Metabolic and endocrine functions

  2. Functions of respiratory passage • Humidify and cool or warm the inspired air. • Bronchial secretions contain secretory immunoglobulin(IgA). • Help to resist infection and maintain integrity of the mucosa. • Prevent foreign bodies entering the alveoli.

  3. Functions of pulmonary circulation. • Acts as filter-clots ,fat cells and gas bubbles.

  4. Fluid exchange and drug absorption. • Low pulmonary hydrostatic pressure tends to pull fluid from alveoli into pulmonary capillaries-keeps the alveoli dry. • Drugs that rapidly pass through the alveolar capillary barrier enter the systemic circulation.

  5. Metabolic and endocrine functions • Surfactant-used in lungs • Prostaglandins and histamine are synthesized or store and released into the blood. • Vasoactive substances are inactivated ,altered or removed from the blood they pass through the lungs.

  6. Prostaglandins • Bradykinin • Adenine derivatives • Serotonin • Nor –epinephrine • Ach

  7. Dead space

  8. Substances activated in the lungs eg • Angiotensin I Converting enzymes Angiotensin II

  9. Dead Space • The part of the respiratory tract where the gaseous exchange does not take place • Function – Purification, Humidification & Air-conditioning • Types –2 • Anatomical dead space volume– Volume of gas in respiratory tract ( nose - terminal bronchiole). • Normal value – 150ml • Physiological dead space volume - Total dead space volume Anatomical DSV + Volume of air in the alveoli which does not take part in the exchange of gas Normal healthy person – Physiological DSV = Anatomical DSV

  10. Variation • Sex: more in males • Age : DS increases with age , because inflated lungs pull the air ways thereby increase the airway diameter. • Body weight: DS increase in proportion with increase in body weight. • Emphysema : loss of elasticity decreases the elastic recoil this causes hyperinflation

  11. Alveolar ventilation

  12. Alveolar ventilation It indicates the volume of air which is utilized for gaseous exchange every minute (TV – DSV) X RR (500 – 150) x12 = 4,200ml/min

  13. Ventilation-Perfusion ratio Ratio of alveolar ventilation and the amount of the blood that perfuses the alveoli • Rate of alveolar ventilation (VA) – 4.2 liters/min • Rate of alveolar perfusion (Q) =5liters • The ventilation-perfusion ratio = VA/Q = 4.2/5 = 0.84 • Important to maintain the alveolar PO2 & PCO2

  14. When VA is normal & Q is also normal =VA/Q is normal • When VA is zero & Q is normal =VA/Q is zero • When VA is normal & Q is zero =VA/Q is infinity

  15. Thank you

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