BSC2086 A P II Exam 4 Study Guide Lesson 14 The Respiratory System Part II Introduction to Gas Exchange Respiration two integrated processes o External Respiration Includes all processes involved in exchanging O2 o CO2 with the environment Internal Respiration Involves the uptake of O2 production of CO2 within individual cells Result of cellular respiration Mitochondria use O2 generate CO2 Three 3 Processes of External Respiration o Pulmonary Ventilation breathing o Gas Diffusion across membranes capillaries o Transport of O2 CO2 Between alveolar capillaries Between capillary beds in other tissues Abnormal external respiration is dangerous o Hypoxia Low tissue oxygen levels o Anoxia Complete lack of oxygen that quickly kills cells o Some tissues require a steady flow of O2 more than others Pulmonary Ventilation tract Pulmonary Ventilation Physical movement of air in out of the respiratory o Provides alveolar ventilation air movement into out of alveoli Atmospheric Pressure The weight of air o Compresses our bodies everything around us o Has several important physiological effects Gas Pressure Volume o Boyle s Law Defines the relationship between gas pressure volume P 1 V In a contained gas External pressure forces molecules closer together Movement of gas molecules exerts pressure on container 1 BSC2086 A P II Exam 4 Study Guide Pressure Airflow to the Lungs o Air flows from area of higher pressure to area of lower pressure Concept similar to diffusion o Pulmonary ventilation causes volume changes that create changes in pressure Volume of thoracic cavity changes with expansion or contraction of diaphragm or rib cage o A respiratory cycle consists of An inspiration inhalation An expiration exhalation 2 BSC2086 A P II Exam 4 Study Guide Pressure changes during inhalation exhalation o Can be measured inside or outside the lungs o Normal atmospheric pressure 1 atm 760 mmHg Intrapulmonary Pressure Intra alveolar Pressure o Relative to atmospheric pressure o During relaxed breathing the difference between atmospheric pressure and intrapulmonary pressure is small About 1 mmHg on inhalation or 1 mmHg on exhalation o Maximum Intrapulmonary Pressure Maximum straining a dangerous activity can increase range from 30 mmHg to 100 mmHg If too high can cause alveolar rupture or hernia Intrapleural Pressure Pressure in space between parietal and visceral pleura o Averages 4 mmHg o Maximum 18 mmHg during powerful inhalation o Usually negative o Positive problem will cause lungs to collapse o Remains below atmospheric pressure throughout respiratory cycle o Caused by elastic recoil of lung tissue pulling on chest wall Two areas linked by pleural fluid Pulls on the chest wall as it recoils As you inhale walls expand pull on the lungs Pneumothorax Allows air into pleural cavity o Breaks fluid bond between the pleurae o Can be caused by Ruptured alveoli through visceral pleura Injury that punctures parietal pleura Atelectasis Collapsed lung result of pneumothorax Respiratory Cycle o Cyclical changes in intrapleural pressure operate the respiratory pump Aids in venous return to heart 3 BSC2086 A P II Exam 4 Study Guide o Tidal Volume VT Amount of air moved in out of lungs in a single respiratory cycle 500 mL Respiratory Muscles o Diaphragm used during normal breathing o External intercostal muscles of the ribs used during normal breathing o Accessory respiratory muscles used during fast breathing Activated when respiration increases significantly Inhalation is ALWAYS active o Muscles used during inhalation Diaphragm Contraction draws air into lungs 75 of normal air movement External Intercostal Muscles Assist inhalation 25 of normal air movement Accessory muscles assist in elevating ribs during fast breathing Sternocleidomastoid Serratus anterior Pectoralis minor Scalene muscles Exhalation can be passive OR active o Passive exhalation relies on relaxation of inhalation muscles recoil of lungs and thoracic cavity elastic rebound o Active exhalation uses muscles during forceful exhalation o Muscles used in active exhalation Internal intercostal muscles transversus thoracis muscles Depress the ribs Abdominal muscles Compress the abdomen Force diaphragm upward 4 BSC2086 A P II Exam 4 Study Guide Compliance An indicator of expandability o Low compliance greater force needed to fill lungs o High compliance less force needed to fill lungs o Factors that affect compliance Connective tissue structure of the lungs Emphysema alveolar tissue damage causes high compliance o Lungs fill to easily but transfer of O2 CO2 less efficient due to damage to respiratory surface Level of surfactant production Low surfactant low compliance Respiratory distress syndrome low compliance Mobility of the thoracic cage Arthritis skeletal disorders reduced compliance Respiratory system adapts to changing oxygen demands by varying o Number of breaths per minute respiratory rate 5 BSC2086 A P II Exam 4 Study Guide o Volume of air moved per breath tidal volume Respiratory Minute Volume VE Amount of air moved per minute o Used to measure pulmonary ventilation o Calculated by Respiratory rate x tidal volume 12 breaths x 500 mL 1 6 gallons 6 liters Alveolar Ventilation VA Amount of air reaching alveoli each minute o Only a part of respiratory minute volume reaches alveolar exchange surfaces space 150 mL Volume of air remaining in conducting passages is anatomic dead o Air entering alveoli contains less O2 more CO2 than atmospheric air Inhaled air mixes with exhaled air o tidal volume anatomic dead space x respiratory rate alveolar ventilation Relationships among VT VE VA o Determined by respiratory rate tidal volume o For a given respiratory rate Increasing tidal volume breathing deeper increases alveolar ventilation rate o For a given tidal volume Increasing respiratory rate breathing faster increases alveolar ventilation Total Lung Volume divided into a series of volumes capacities useful in diagnosing problems o Four 4 Pulmonary Volumes Resting Tidal Volume Vt in a normal respiratory cycle Expiratory Reserve Volume ERV after a normal exhalation Residual Volume after maximum exhalation Inspiratory Reserve Volume IRV after a normal inspiration o Four 4 Calculated Respiratory Capacities Inspiratory Capacity tidal volume inspiratory reserve volume Functional Residual Capacity FRC expiratory reserve volume residual volume Vital Capacity expiratory reserve volume tidal volume inspiratory reserve volume Total Lung Capacity vital capacity
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