BSC 2086 1st Edition Lecture 17 Outline of Last Lecture I Introduction to Respiratory System II Components of Respiratory System III Upper Respiratory Tract IV Larynx V Trachea VI Lungs Outline of Current Lecture I Introduction to Gas Exchange II Pulmonary Ventilation III Gas Exchange Current Lecture I Introduction to Gas Exchange a External respiration all processes needed to exchange O2 and CO2 with the environment i Three processes 1 Pulmonary ventilation breathing 2 Gas diffusion across the membranes and capillaries 3 Transport of oxygen and carbon dioxide between a Alveolar capillaries b Capillary beds in other tissues ii Abnormalities 1 Hypoxia low oxygen tissue levels 2 Anoxia complete lack of oxygen which quickly kills cells II b Internal respiration result of cellular respiration i Uptake of O2 and production of CO2 in each individual cell 1 Mitochondria uses oxygen and makes water Pulmonary Ventilation a Physical movement of air in and out of respiratory tract b Provides alveolar ventilation which moves air in and out of alveoli c Atmospheric pressure weight of air that compresses our bodies i Several physiological effects d Gas pressure and volume i Boyles law defines this relationship ii P 1 V iii In a contained gas the external pressure forces molecules closer together 1 This movement of gas molecules exerts pressure on the container e Pressure and airflow to the lungs i Similar to diffusion air flows from an area of high pressure to one with lower pressure ii Pulmonary ventilation volume changes cause a change in pressure 1 Expansion or contraction of the diaphragm or rib cage will cause a volume change of the thoracic cavity iii Respiratory cycle 1 Inspiration inhalation a Thoracic cavity expands diaphragm pushes down volume increases in thoracic cavity allowing the lungs to expand b When pressure drops lower than atmospheric pressure air flows into lungs 2 Expiration exhalation a Usually doesn t involve muscles b Ribs compress back down into there normal shape 3 Pressure changes during either of these can be measured either inside or outside of the lungs a Normal atmospheric pressure i 1 atm 760 mm Hg iv Intrapulmonary Pressure aka intraalveolar pressure 1 Air pressure inside alveolus 2 Relative to atmospheric pressure 3 Difference between atmospheric pressure and intrapulmonary pressure is small in relaxed breathing a About 1 mm Hg on exhalation b About 1 mm Hg on inhalation 4 Maximum intrapulmonary pressure a Max straining is a dangerous activity and can increase in range from 30 mmHg to 100 mmHg b If it becomes too high alveolar rupture or hernia can occur v Intrapleural pressure 1 Pressure between parietal and visceral pleura 2 Averages 4 mmHg with a maximum of 18 mmHg during powerful inhalation 3 Stays below the atmospheric pressure during the respiratory cycle 4 Cause by elastic recoil of lung tissue pulling on chest wall vi Chest wall injuries 1 Pneumothorax fluid enters pleural cavity and breaks the fluid bond between the plurae 2 Atelectasis result of pneumothorax a Collapsed lung f Respiratory Cycle i Respiratory pump operated by cyclic changes in intrapleural pressure 1 This helps in venous return to the heart ii Tidal volume Vt about 500 mL 1 The amount of air that goes in and out of the lungs in a single respiratory cycle iii In a normal lung the intrapleural pressure is always negative compared to the intrapulmonary pressure g Respiratory Muscles i Diaphragm necessary for normal breathing ii External intercostal muscles of ribs necessary for normal breathing iii Accessory respiratory muscles necessary for fast breathing and activated when respiration increases significantly h Breathing mechanics i Inhalation is always active 1 Diaphragm its contraction draws air into the lungs a 75 of normal air movement 2 External intercostal muscles help inhalation and are responsible for 25 of air movement 3 Accessory muscles used to elevate ribs in fast breathing a Sternocleidomastoid b Serratus anterior c Pectoralis minor d Scalene muscles ii Exhalation can be passive or active 1 Passive relaxation of inhalation muscles and elastic rebound which involves the recoil of both the lungs and the thoracic cavity 2 Active uses respiratory muscles for forceful exhalation a Internal intercostal and transversus thoracic muscles depress the ribs i j b The abdominal muscles compress abdomen and push the diaphragm up iii Compliance indicates expandability 1 Low compliance greater force needed to fill lungs 2 High compliance less force to fill lungs 3 Factors a Connective tissue structure of lungs i Emphysema causes high compliance due to alveolar damage b Amount of surfactant production i Respiratory distress syndrome causes low compliance c Mobility of thoracic cage i Compliance reduced by arthritis or skeletal disorders Respiratory rates and Volumes i Adapts to changing oxygen demands by changing 1 Respiratory rate number of breaths per minute 2 Tidal volume volume of air moved per breath ii Respiratory Minute Volume VE used to measure pulmonary ventilation by measuring amount of air moved per minute 1 Respiratory rate 12 breaths x tidal volume 500 mL about 1 6 gallons 6 liters iii Alveolar Ventilation VA 1 Tidal volume anatomic dead space x respiratory rate 2 Amount of air reaching alveoli per minute 3 Not all of respiratory minute volume reaches the alveolar exchange surfaces a Anatomic dead space is the volume of air remaining in conducting passages about 150 mL 4 Compared to atmospheric air air going into alveoli has less O 2 and more CO2 a Due to mixture of inhaled and exhaled air iv Relationships between VT VE VA 1 For any given respiratory rate increasing the tidal volume by breathing deeper will increase alveolar ventilation rate 2 For any given tidal volume increasing respiratory rate by breathing faster will increase alveolar ventilation Respiratory Performance and Volume Relationships i Total lung volume is able to diagnose problems by being divided into a series of volumes and capacities ii Four pulmonary volumes III 1 Resting tidal volume Vt normal respiratory cycle 2 Expiratory reserve volume ERV after a normal exhalation 3 Residual volume after max exhalation 4 Inspiratory reserve volume IRV after a normal inhalation iii Four calculated respiratory capacities 1 Inspiratory capacity TV IRV 2 Functional residual capacity FRC ERV RV residual volume is the air left in the lungs after normal expiration 3 Vital capacity VC ERV TV IRV 4 Total lung capacity VC RV
View Full Document
Unlocking...