Respiratory System 5 December 2018 Respiratory System

Respiratory System Pulmonary Ventilation Gas Transfer Across Alveolar/capillary Membrane Transport of O2 & CO2 in Blood Regulation of Ventilation 5 December 2018 Respiratory System

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

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

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

Introduction Fragile barrier protected against Trauma, dehydration, freezing Fragile membrane imposes Small barrier to gas exchange 5 December 2018 Respiratory System

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

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

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

Respiratory System Gas exchange organ Each divided into lobes Consists of 2 lungs Each divided into lobes 5 December 2018 Respiratory System

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

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

5 December 2018 Respiratory System From: www.coheadquarters.com/penlibr/myphysiology 5 December 2018 Respiratory System

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

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

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

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

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

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

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

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

5 December 2018 Respiratory System From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System

The Respiratory Airways From: www.coheadquarters.com/penlibr/myphysiology 5 December 2018 Respiratory System

Alveolar Capillary Membrane From Jennifer Shaw: PPT “The Respiratory System” 5 December 2018 Respiratory System

Alveolar Capillary Membrane 5 December 2018 Respiratory System

Alveolar Capillary Membrane Made up of Alveolar epithelium Single layer epithelial cells Basement membrane Elastic collageneous tissue Capillary endothelium Single layer endothelial cells From: www.pdh-odp.co.uk/diffusion.htm 5 December 2018 Respiratory System

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: www.coheadquarters.com/penlibr/myphysiology 5 December 2018 Respiratory System

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

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

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

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

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

Surfactant Thus a hydrophobic surface is exposed to the air Has a much lower ST 5 December 2018 Respiratory System

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

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

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

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

Effects of Surfactant 5 December 2018 Respiratory System