Respiratory Physiology L1 Student PDF

BIOM2012 - Systems Physiology: Respiratory System L1 Dr. Jacky Suen [email protected] Credit: A/Prof Stephen Anderson and Dr. Hardy Ernst Learning Objectives Pulmonar...

BIOM2012 - Systems Physiology: Respiratory System L1 Dr. Jacky Suen [email protected] Credit: A/Prof Stephen Anderson and Dr. Hardy Ernst Learning Objectives Pulmonary Ventilation and Respiratory mechanics Gas exchange Gas transport Blood pH regulation Control of Respiration Resources Marieb, Elaine, and Katja Hoehn. Human Anatomy and Physiology, Global Edition, 2018 Sherwood, Lauralee. Human Physiology : From Cells to Systems, Cengage, 2015. Silverhorn. Human Physiology: An Intergrated Approach, 8th Edition West’s Respiratory Physiology: The Essential West’s Pulmonary Pathophysiology: The Essential Differences between lecture slides and handout (on UQ Learn). This is to encourage note taking in order to enhance your learning. Basic Function Gas exchange - homeostasis of CO2, O2 Acid-base balance - blood pH Respiratory physiology is heavily related to its anatomy  Respiratory System Definition: “The organs and tissues involved in gas exchange” Nose but also Mouth Diaphragm Pharynx Ribs Larynx Pleura Trachea Alveoli Bronchi Capillaries Lungs BonkersArt, Adobe Stock  Conducting & Respiratory Zones Functionally, the respiratory system is divided into the conducting and respiratory zones, each with distinct roles. can differentiate terminal vs respiratory bronchioles Increase in surface area of the respiratory zone Respiratory Zone Pulmonary arteries branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Gas exchange through passive diffusion Oxygenated blood returns via pulmonary veins to the left atrium McKinley & O’ Loughlin 2012 Cellular transition across zones Adapted from Ganong's Review of Medical Physiology. pseudostratified layer squamous cells, single-layered with submucosal glands continuous membrane that facilitates diffusion  Cells of the Alveoli There are three types of cells that line the alveoli: Type I pneumocytes / Type 1 alveolar cells Most abundant (97%), involved in gas exchange. Type II pneumocytes / Type 2 alveolar cells Produce and secrete surfactant, a phospholipid (both hydrophilic and hydrophobic) that lines the inner alveolar surface to reduce surface tension. Alveoli macrophages Phagocytic cells that remove foreign debris and pathogens. Fick’s Law of Diffusion Shorter distance – Greater rate of diffusion Greater surface area – Great rate of diffusion  The pleurae of the lungs Each lung is encased in a thin, two-layered, fluid-filled membrane called the pleura. Inner visceral pleura, outer parietal pleura, and between pleural cavity filled with pleural fluid. Functions of the pleura Lubrication: reduces friction during breathing Surface tension: helps position of the lungs against the thoracic wall Division: isolates the respiratory system from other major organs opentextbc.ca/anatomyandphysiology Learning Objectives Pulmonary Ventilation and Respiratory mechanics Gas exchange Gas transport Blood pH regulation Control of Respiration How do we breathe?  Breathing: Pulmonary Ventilation Boyle’s law - the absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies, if the temperature and amount of gas is unchanged (confined). an inverse relationship between pressure and volume P1V1 = P2V2 when volume increases pressure decreases and vice versa  Pulmonary Ventilation Pulmonary ventilation refers to the moving of air in and out of the lungs. A mechanical process that depends on volume changes in the thoracic cavity. ∆ Volume → ∆ Pressure → flow of gases Such changes in volume are driven by the contraction/relaxation cycling of intercostal muscles and the diaphragm.  Rib cage wants to expand Surface tension, lung naturally wants to recoil Quick recap from respiratory anatomy Marieb Fig 22.16  Quick recap from respiratory anatomy At rest No difference in pressure No air movement Sherwood Fig 13.7 Marieb Fig 22.16  1. Inspiratory muscles contract 2. Thoracic cavity volume increases 3. Intrapulmonary volume increases 4. Intrapulmonary pressure decreases (-1 mm Hg) 5. Air flows in until pressure equalises Intrapleural pressure drops further because an inflated lungs want to recoil more Sherwood Fig 13.12 And expiration Marieb Fig 22.16 Sherwood Fig 13.12 Lung Pressures Key factors influencing negative intra-pleural pressure Surface tension Pleural fluid provides surface tension between pleural layers Elastic force by the lungs (inwards) Elastic tissue in lung recoils and pulls lung inwards Visceral pleura pulled inwards Elastic force by the thoracic cage (outwards) Thoracic wall tends to naturally pull away from lung Parietal pleura pulled outwards  Pressure gradients: quiet breathing 0.50 Note this is quiet breathing (eupnea). Volume change 0.25 Tidal volume is the amount of air that moves in or out of the lungs with each (L) 0 +2 Intra-alveo lar pres respiratory cycle. 400-500 ml. sure Pressure 0 relative to patm -2 Transpulmonary pressure (cm H2O) -4 Transpulmonary pressure pressure difference across the whole lung, -6 between alveolar space and pleural space -8 Intra-pleural pressure ptp = palv – pip 1mmHg = 1.36 cmH2O the net distending pressure applied to the lung by -4mmHg = -5.44 cmH2O Inspiration Expiration contraction (and relaxation) of the inspiratory muscles is force that keeps the lungs open Strictly speaking, transpulmonary pressure should be pressure in trachea minus the intrapleural pressure. But pressure in alveoli is same as pressure in airways at least at beginning and end of each breath. That is, end-expiratory or end-inspiratory alveolar pressure is 0 cm H2O at the beginning of each breath. So alveolar-distending pressure can be referred to as the transpulmonary pressure.  ptp = palv – pip = patm = 0 Marieb Fig 22.15 Modes of Breathing: Quiet vs Forced breathing Quiet breathing (normal breathing / eupnea) Occurs at rest, without cognitive thought Inspiration: diaphragm, external intercostal muscles Expiration: relaxation of diaphragm and intercostal muscles Diaphragmic vs costal breathing Forced breathing (hypernea) Requires extra muscle contractions in BOTH inspiration and expiration ∆ Volume → ∆ Pressure → flow of gases  Forced breathing Hypereupnea: Fast-forced breathing Exhalation Internal intercostal muscles Inspiration Accessory muscles and transversus thoracis depress the ribs assist external intercostal muscles to At very rigorous breathing elevate the ribs and Exhalation enlarge the thorax Abdominal muscles compress abdominal 1) Scalene muscles (elevate 1st and 2nd contents & reduce the volume of the thoracic ribs) cavity 2) Serratus anterior and posterior 1) External & internal 3) Pectoralis minor and major obliques 2) Transversus abdominis 4) Sternocleidomastoid 3) Rectus abdominis Summary Can you describe the relationship between pulmonary pressure and volume? Can you explain the steps involved in quiet inspiration? Contractions of which muscles are involved in quiet expiration? A. Abdominal muscles B. Internal intercostal muscles C. Diaphragm and external intercostal muscles D. Diaphragm and internal intercostal muscles E. None of the above Which of the following is not related to a negative Pip? A. Recoil of the lungs B. Alveolar surface tension C. Airway resistance D. Elastic force of the thoracic cage E. None of the above