Chapter 16 Respiratory Physiology Highlighted information is what Trombley focused on during the review session Section 1 The Respiratory System Respiratory system is divided into 2 zones o Respiratory zone site of gas exchange between air and blood o Conducting zone site that moves air into the respiratory zone warms humidifies filters and cleans the air and produces sound in the larynx as air passes over the vocal folds Mucus traps small particles and cilia move it to the pharynx Respiration includes 3 functions o Ventilation breathing o Gas exchange CO2 for O2 in the lungs and O2 for CO2 in the tissue o Oxygen Utilization tissues using O2 for cell respiration o External Respiration ventilation gas exchange in the lungs o Internal Respiration gas exchange in tissues oxygen utilization Gas exchange occurs through diffusion o O2 is higher in the lungs than in the blood so O2 diffuses into the blood o CO2 is higher in the blood than in the lungs so CO2 diffuses into lungs Alveoli Air sacs in the lungs where gas exchange occurs 2 types of alveolar cells o Type I the cells where the majority of gas exchange occurs o Type II the cells that secrete pulmonary surfactant and reabsorb Na and H2O to prevent fluid buildup Air Flow Nasal cavity pharynx larynx trachea right and left primary bronchi secondary bronchi tertiary bronchi terminal bronchioles respiratory bronchioles alveoli The diaphragm divides the anterior body into 2 parts o Abdominopelvic Cavity area below the diaphragm o Thoracic Cavity area above the diaphragm and contains the heart large blood vessels trachea esophagus thymus within the central mediastinum and the lungs Parietal plura superficial layer lining the inside of the thoracic wall Visceral plura deep layer that covers the surface of the lungs Section 2 Physical Aspects of Ventilation Subatmospheric or Negative Pressure pressure atmospheric pressure Inspiration Inhalation negative pressure because the intrapulmonary pressure atmospheric pressure 3mmHg Expiration Exhalation positive pressure because the intrapulmonary pressure atmospheric pressure 3mmHg Intrapleural pressure intrapulmonary and atmospheric pressure during both inhalation and exhalation Transpulmonary Pressure The difference between the intrapulmonary and intrapleural pressure important for keeping the lungs pressed against the thoracic wall and for allowing the lungs to expand during inhalation to its volume The pressure of a given quantity of gas is inversely proportional Boyle s Law o Increase in lung volume during inspiration decrease in intrapulmonary pressure to subatmospheric levels air influx o Decrease in lung volume during expiration increase in intrapulmonary pressure above atmospheric levels air efflux During ventilation pressure differences between the ends of the conducting zone occur due to changing lung volume Compliance elasticity and surface tension are important physical properties that affect lung function o Compliance lungs ability to expand stretch o Elasticity lungs ability to recoil return to original size after stretch o Surface Tension alveoli resistance to stretch Lung Compliance The change in lung volume per change in transpulmonary pressure or V P Law of Laplace The pressure within an alveolus is directly proportional to its surface tension and inversely proportional to its radius o Small alveoli would be at a high risk for collapsing without surfactant Surfactant A mixture of phospholipids and proteins produced by type II alveolar cells that reduces the surface tension of the alveoli and contributes to the elastic properties of the lungs o Small alveoli have a higher concentration of surfactant to prevent collapse at high pressures Respiratory Distress Syndrome RDS A lung disease of the newborn in which a deficiency in surfactant causes an abnormally high surface tension in the alveoli and thus possible alveoli collapse Acute Respiratory Distress Syndrome ARDS A lung condition in adults caused by septic shock reduced lung compliance and reduced surfactant Section 3 Mechanics of Breathing Between the bony portions of the rib cage are 2 layers of intercostal muscles o External intercostal muscles o Internal intercostal muscles Inhalation thoracic and lung volume increase vertically when diaphragm contracts flattens and laterally when parasternal and external intercostals raise the ribs decrease in intrapulmonary pressure air influx Expiration thoracic and lung volume decrease vertically when diaphragm relaxes dome and laterally when external and parasternal intercostals relax for quiet expiration or internal intercostals contract in forced expiration to lower the ribs increase in intrapulmonary pressure air efflux Muscles involved in breathing include o The scalenes pectoralis minor and sternocleidomastoid are involved in forced inhalation and in quite exhalation when relaxed o Abdominal muscles are also involved in forced exhalation Spirometry Subject breathes into and out of a device that records volume and frequency of air movement on a spirogram to measure lung volumes and capacities it can also diagnose restrictive and obstructive lung disorders Know the terms used to describe lung volumes and capacities table below o Vital capacity inspiratory reserve volume expiratory reserve o Functional residual capacity residual volume expiratory reserve volume tidal volume volume o Total minute volume tidal volume x breaths per minute 6L min Restrictive Disorders Lung tissue is usually damaged and vital capacity is reduced but forced expiration is normal o Pulmonary fibrosis and emphysema Obstructive Disorders Lung tissue and vital capacity is normal but forced expiration is reduced Usually caused by inflammation mucus secretion and bronchioles constriction o Asthma Section 4 Gas Exchange in the Lungs A barometer can be used to measure atmospheric pressure which at sea level is 760 mmHg or 1 atm Dalton s Law The total pressure of a gas mixture is equal to the sum of each individual gas partial pressure the pressure that a particular gas in a mixture exerts independently Partial pressure total pressure of the individual gas x the of the individual gas in mixture The total atmospheric pressure is constant so the addition of any molecule to a mixture will cause the other molecules partial pressures to decrease o Pdry PN2 PO2 PCO2 where PO2 159 mmHg o Pwet PN2 PO2 PCO2 PH20 where PO2 150 mmHg When air enters the lungs the small amount of water vapor in the lungs will contribute to
View Full Document
Unlocking...