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Respiratory System 5 December 2018 Respiratory System
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Respiratory System Pulmonary Ventilation
Gas Transfer Across Alveolar/capillary Membrane Transport of O2 & CO2 in Blood Regulation of Ventilation 5 December 2018 Respiratory System
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Introduction Animal cells obtain energy by Therefore
Oxidative breakdown of nutrients Therefore They must be continually supplied with oxygen Carbon dioxide must be removed 5 December 2018 Respiratory System
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Introduction In lower forms of life In mammals
Simple diffusion is adequate In mammals Simple diffusion is not adequate Had to develop specialized system for Oxygen supply Carbon dioxide elimination 5 December 2018 Respiratory System
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Introduction To achieve this they use two systems Respiratory system
Cardiovascular system Gas exchanger Fragile barrier between external & internal environment 5 December 2018 Respiratory System
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Introduction Fragile barrier protected against
Trauma, dehydration, freezing Fragile membrane imposes Small barrier to gas exchange 5 December 2018 Respiratory System
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Respiratory System Respiration is the term used to include
Internal respiration Covered during biochemistry course External respiration Gas exchange Ventilation Gas transfer (alveolar/capillary) Blood gas transport External respiration is the absorption of O2 from the external environment and the removal of CO2 from the body Internal respiration: utilization of O2 and the production of CO2 by the cells and the gaseous exchange between the cells and fluid medium 5 December 2018 Respiratory System
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Respiratory System Respiratory system is made up of
Gas exchange organ (lungs) The pump that ventilates the lungs which include Chest wall Respiratory muscles Respiratory center 5 December 2018 Respiratory System
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Respiratory System At rest a normal human breathes
12 to 15 times per minute 500 mls of air per breath 6 to 8 liters of air inspired or expired per min 5 December 2018 Respiratory System
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Respiratory System Gas exchange organ Each divided into lobes
Consists of 2 lungs Each divided into lobes 5 December 2018 Respiratory System
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Structure of Lungs The lungs comprise of 2 tree like structures
Vascular tree made up of Arteries and veins Connected by capillaries From Textbook of Work Physiology by Astrand, Rodahl, Dahl & Stromme 5 December 2018 Respiratory System
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Structure and Functions of Lungs
Airway tree, embedded in elastic connective tissue From Textbook of Work Physiology by Astrand, Rodahl, Dahl & Stromme 5 December 2018 Respiratory System
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5 December 2018 Respiratory System
From: 5 December 2018 Respiratory System
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The Airways The trachea divides into 2 main bronchi
The bronchi divides Many times to form bronchioles Between the trachea and alveolar sac Air ways divides 23 times (23 generations) From: Nunn’s Applied Respiratory physiology; 5th Ed 5 December 2018 Respiratory System
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The Airways The first 3 generations of conducting zone plus the trachea Contain cartilage to prevent airway collapse Trachea, main bronchi cartilage is U shaped Lobar, segmental bronchi have small plates From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System
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The Airways The bronchioles and terminal bronchioles
In the bronchioles Cartilage disappears The smallest airways in the conducting zone Are the terminal bronchioles The bronchioles and terminal bronchioles Suspended by elastic tissues in the lung parenchyma From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System
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The Airways The first 16 generation form
Conducting zone of the airways Transport gas from & to exterior Made up of Bronchi Bronchioles Terminal bronchioles From Textbook of Work Physiology by Astrand, Rodahl, Dahl & Stromme 5 December 2018 Respiratory System
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The Airways The remaining 7 generation form the
Transitional & respiratory zone Made up of Respiratory bronchioles Alveolar duct Alveoli Gas exchange takes place in this zone From Textbook of Work Physiology by Astrand, Rodahl, Dahl & Stromme 5 December 2018 Respiratory System
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The Airways The multiple divisions Hence the velocity of airflow
Greatly increase the cross sectional area of the airways 2.5 cm2 in the trachea 11,800 cm2 in the alveoli Hence the velocity of airflow Decline to very low values in small airways From Textbook of Work Physiology by Astrand, Rodahl, Dahl & Stromme 5 December 2018 Respiratory System
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Respiratory Zone Alveoli Alveolar capillary membrane
Branch of pulmonary artery Alveoli Surrounded by pulmonary capillaries Alveolar capillary membrane Very thin < 0.5 m Alveolar epithelium Interstitial fluid Capillary endothelium Branch of pulmonary vein Respiratory bronchiole The alveolar capillary membrane Very thin Composed of alveolar membrane, interstitial fluid, capillary endothelium Air is brought to one side of the interface by ventilation Blood is brought to the other side of the interface by the pulmonary circulation Alveolus Alveoli with capillary network (From Hassen Taha Sherrif ) Textbook of Physiology CD 5 December 2018 Respiratory System
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Respiratory Zone There are 300 millions alveoli in human
Branch of pulmonary artery There are 300 millions alveoli in human Total Surface Area of alveolar wall in contact with capillary = 75 m2 Compare skin SA = 1.8 m2 Branch of pulmonary vein Respiratory bronchiole The alveolar capillary membrane Very thin Composed of alveolar membrane, interstitial fluid, capillary endothelium Air is brought to one side of the interface by ventilation Blood is brought to the other side of the interface by the pulmonary circulation Alveolus Alveoli with capillary network (From Hassen Taha Sherrif ) Textbook of Physiology CD 5 December 2018 Respiratory System
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5 December 2018 Respiratory System
From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System
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The Respiratory Airways
From: 5 December 2018 Respiratory System
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Alveolar Capillary Membrane
From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System
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Alveolar Capillary Membrane
5 December 2018 Respiratory System
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Alveolar Capillary Membrane
Made up of Alveolar epithelium Single layer epithelial cells Basement membrane Elastic collageneous tissue Capillary endothelium Single layer endothelial cells From: 5 December 2018 Respiratory System
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Alveolar-Capillary membrane
Alveolar capillary membrane thickness can increase if Basement membrane is distended with fluid Pulmonary oedema Fluid accumulates in the alveolar space From: 5 December 2018 Respiratory System
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Surface Tension Any air – liquid interface develop surface tension
When water forms interface with air Water molecules on the surface of the water have strong attraction force for one another Water surface attempt to contract 5 December 2018 Respiratory System
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Surface Tension In the alveolar the water on the inner side of alveolar tend to contract This causes Powerful collapsing tendency of the alveoli Surface tension elastic force of lungs 5 December 2018 Respiratory System
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Laplace’s law P = (2T)/R In the alveoli
P = pressure exerted by surface tension of bubble T = surface Tension R = radius of the bubble (alveolus) In the alveoli During expiration R decreases P increases, tendency to collapse increases 5 December 2018 Respiratory System
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Surfactant Surface active phospholipids
Synthesized by type II alveolar cells (granular pneumonocytes) It is a complex mixture of Phospholipids, proteins & Ca++ Dipalmitoylphosphatidylcholine Surfactant apoproteins Calcium ions 5 December 2018 Respiratory System
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Surfactant Phospholipids Responsible for reducing the surface tension
Does not dissolve uniformly in the water lining the alveolar surface One portion of molecule is hydrophilic Dissolves in water The other portion is hydrophobic Oriented towards air 5 December 2018 Respiratory System
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Surfactant Thus a hydrophobic surface is exposed to the air
Has a much lower ST 5 December 2018 Respiratory System
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Effects of Surfactant The amount of reduction of ST by surfactant
Proportional to concentration of surfactant on the surface From: Nunn’s Applied Respiratory physiology; 5th Ed 5 December 2018 Respiratory System
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Effects of Surfactant During inspiration Volume of alveolar increases
With fixed amount of surfactant Conc. of surfactant on surface decreases Increases ST Prevent further increase in surface of alveoli From: Nunn’s Applied Respiratory physiology; 5th Ed 5 December 2018 Respiratory System
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Effects of Surfactant During expiration Volume of alveoli decreases
Conc of surfactant on the surface increases Decreases ST Decrease the tendency to collapse From: Nunn’s Applied Respiratory physiology; 5th Ed 5 December 2018 Respiratory System
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Effects of Surfactant Thus
Stabilizing the alveoli against tendency to collapse Diminish the force required for expansion of the lung Reduces the work of breathing From: Nunn’s Applied Respiratory physiology; 5th Ed 5 December 2018 Respiratory System
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Effects of Surfactant 5 December 2018 Respiratory System
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