PHYSIOLOGY OF RESPIRATION PHYSIOLOGY OF RESPIRATION (MECHANISM & CONTROL OF BREATHING) (MECHANISM & CONTROL OF BREATHING) (I) (I) Dr.G.Moinuddin Ghori,PhD Dr.G.Moinuddin Ghori,PhD Prof.of Physiology,College of Prof.of Physiology,College of Medicine,King Saud Bin Medicine,King Saud Bin Abdulaziz University for Abdulaziz University for Health Sciences,RIYADH Health Sciences,RIYADH (Pre-professional class lecture 5) (Pre-professional class lecture 5)
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PHYSIOLOGY OF RESPIRATION PHYSIOLOGY OF RESPIRATION (MECHANISM & CONTROL OF BREATHING)(MECHANISM & CONTROL OF BREATHING)
(I)(I)
Dr.G.Moinuddin Ghori,PhDDr.G.Moinuddin Ghori,PhD
Prof.of Physiology,College of Prof.of Physiology,College of Medicine,King Saud Bin Abdulaziz Medicine,King Saud Bin Abdulaziz University for Health University for Health Sciences,RIYADHSciences,RIYADH(Pre-professional class lecture 5)(Pre-professional class lecture 5)
OBJECTIVESOBJECTIVES
**StructureStructure of the lungs & thoracic cavity of the lungs & thoracic cavity
* The * The VentilationVentilation process. process.
**Intrapulmonary & Intrapleural Intrapulmonary & Intrapleural pressurespressures during ventilation during ventilation
**MechanismMechanism of Inspiration & Expiration. of Inspiration & Expiration. Respiratory musclesRespiratory muscles
**SpirometrySpirometry (to measure Volumes & (to measure Volumes & Capacities as Lung Function Tests)Capacities as Lung Function Tests)
RESPIRATIONRESPIRATION
• The term The term RespirationRespiration includes includes 4 -4 - separate functions:-separate functions:-– Pulmonary Ventilation:- Pulmonary Ventilation:-
• Inflow and outflow of airInflow and outflow of air
– Gas exchange: O2 and CO2:-Gas exchange: O2 and CO2:-• Between air and capillaries in the lungs.Between air and capillaries in the lungs.• Between systemic capillaries and tissues of the Between systemic capillaries and tissues of the
body.body.
– Transport of O2 &CO2 in bloodTransport of O2 &CO2 in blood– Regulation of ventilationRegulation of ventilation
• Diaphragm:Diaphragm:– Sheets of striated muscle divides anterior Sheets of striated muscle divides anterior
body cavity into 2 parts.body cavity into 2 parts.• Above diaphragm: thoracic cavity:Above diaphragm: thoracic cavity:
– Contains heart, large blood vessels, trachea, Contains heart, large blood vessels, trachea, esophagus, thymus, and lungs.esophagus, thymus, and lungs.
• Below diaphragm: abdominopelvic cavity:Below diaphragm: abdominopelvic cavity:– Contains liver, pancreas, GI tract, spleen, Contains liver, pancreas, GI tract, spleen,
and genitourinary tract.and genitourinary tract.• Intrapleural space:Intrapleural space:
– Space between visceral and parietal pleurae.Space between visceral and parietal pleurae.
CONDUCTING ZONECONDUCTING ZONE
The structures, air The structures, air passes through before passes through before reaching the reaching the respiratory zone.respiratory zone.
• Warms and humidifies Warms and humidifies inspired air.inspired air.
• Filters and cleans:-Filters and cleans:-– Mucus secreted to Mucus secreted to
trap particles in the trap particles in the inspired air.inspired air.
RESPIRATORY ZONERESPIRATORY ZONE
• Region of gas Region of gas exchange exchange between air between air and blood.and blood.
• Includes Includes respiratory respiratory bronchioles bronchioles and alveolar and alveolar sacs.sacs.
• Must contain Must contain alveoli.alveoli.
ALVEOLIALVEOLI
• Polyhedral in shape and clustered like units of Polyhedral in shape and clustered like units of honeycomb:-honeycomb:-
• –– 300 million air sacs (alveoli).300 million air sacs (alveoli).– Large surface area (60Large surface area (60––80 m80 m22).).– Each alveolus is 1 cell layer thick.Each alveolus is 1 cell layer thick.– Total air barrier is 2 cells across (2 Total air barrier is 2 cells across (2 m).m).
• 2 types of cells:-2 types of cells:-– Alveolar type I:Alveolar type I:
• Structural cells.Structural cells.– Alveolar type II:Alveolar type II:
• Secrete surfactant.Secrete surfactant.
INTRAPULMONARY AND INTRAPULMONARY AND INTRAPLEURAL PRESSURES INTRAPLEURAL PRESSURES (continued)(continued)
• During inspiration:-During inspiration:-– Atmospheric pressure is > Atmospheric pressure is >
intrapulmonary pressure (-3 mm Hg).intrapulmonary pressure (-3 mm Hg).
• During expiration:-During expiration:-– Intrapulmonary pressure (+3 mm Hg) Intrapulmonary pressure (+3 mm Hg)
is > atmospheric pressure.is > atmospheric pressure.
PULMONARY VENTILATIONPULMONARY VENTILATION
MECHANICS OF PULMONARY MECHANICS OF PULMONARY
VENTILATIONVENTILATION
• EXPANSION & CONTRACTION OF LUNGS EXPANSION & CONTRACTION OF LUNGS DUE TO :- DUE TO :-
- Downward & upward movement of - Downward & upward movement of
• Active process:-Active process:-– Contraction of diaphragm, increases thoracic Contraction of diaphragm, increases thoracic
volume vertically.volume vertically.
• Pressure changes for inspiration:-Pressure changes for inspiration:-– Alveolar changes from 0 to Alveolar changes from 0 to ––3 mm Hg.3 mm Hg.– Intrapleural changes from Intrapleural changes from ––4 to 4 to ––6 mm Hg.6 mm Hg.– Transpulmonary pressure = +3 mm Hg.Transpulmonary pressure = +3 mm Hg.
ExpirationExpiration
• Quiet expiration is a passive process:-Quiet expiration is a passive process:-– After being stretched by contractions of the After being stretched by contractions of the
diaphragm and thoracic muscles; the diaphragm, diaphragm and thoracic muscles; the diaphragm, thoracic muscles, thorax, and lungs recoil.thoracic muscles, thorax, and lungs recoil.
– Decrease in lung volume raises the pressure within Decrease in lung volume raises the pressure within alveoli above atmosphere, and pushes air out.alveoli above atmosphere, and pushes air out.
• Pressure changes:Pressure changes:--– Intrapulmonary pressure changes from Intrapulmonary pressure changes from ––3 to +3 mm 3 to +3 mm
Hg.Hg.– Intrapleural pressure changes from Intrapleural pressure changes from ––6 to 6 to ––3 mm Hg.3 mm Hg.– Transpulmonary pressure = +6 mm Hg.Transpulmonary pressure = +6 mm Hg.
Pulmonary Function TestsPulmonary Function Tests
• Assessed by spirometry.Assessed by spirometry.• Subject breathes into a closed system in which air is Subject breathes into a closed system in which air is
trapped within a bell floating in Htrapped within a bell floating in H220.0.
• The bell moves up when the subject exhales and down The bell moves up when the subject exhales and down when the subject inhales.when the subject inhales.
