PET3322 Study Guide for Exam 4 The Respiratory System Major Functions Provide blood with oxygen and dispose of CO2 Gas exchange is simple diffusion In order for respiration to occur 4 processes must happen o Pulmonary ventilation breathing moving air into and out of lungs o External respiration gas exchange between lungs and blood o Transport of respiratory gasses o Internal respirations movement of O2 from blood and tissue cells movement of CO2 from the tissue cells into the blood Respiratory membrane has 3 main parts o 1 wall of the capillary o 2 wall of the alveolus o 3 space between these two walls Conducting Zone o Bronchi Subdivided into secondary bronchi each supplying a lobe of the lungs There are 23 orders of branching in the lungs that air must pass through Contain cartilage o Bronchial Tree Bronchi split into Bronchioles Bronchioles contain a layer of smooth muscle and lack cartilage support Note big tubes of the conducting zone contain cartilage small tubes lack cartilage Branching of the Bronchiole Tree Trachea secondary bronchi tertiary bronchi bronchioles terminal bronchioles Respiratory Zone o Begins at the terminal bronchioles and feed into the respiratory bronchioles o alveoli are present o Microscopic Airways Terminal bronchioles start respiratory bronchioles alveolar ducts alveolar sacs alveoli o Alveoli are the smallest alveolar sacs are made up of alveoli etc o O2 goes from high low so if you take a deep breath you have high O2 in lungs tubes which then travels to the blood where O2 levels are low Hence simple diffusion o There are 300 million alveoli This makes up most of the lung s volume There are tiny sacs on alveoli don t confuse with alveolar sacs which account for a greater surface area for gas exchange capillaries cover alveoli o 6 capillaries cover the alveoli o The alveolar walls and capillary walls are fused at their basal laminas making the air Air Blood Barrier blood barrier o There is fluid between the lungs and the blood capillaries o O2 diffuses into the cells and CO2 diffuses out of the cells o Alveolar wall Made of a single layer of epithelial cells Permit gas exchange by simple diffusion Secretes ACE angiotensin converting enzyme Blood Circulates to the Lungs o Two circulations pulmonary and bronchial o Pulmonary arteries supply systemic blood to be oxygenates o Pulmonary veins carry oxygenated blood from respiratory zones to the heart Mechanics of breathing aka Pulmonary ventilation Breathing is different than respiration Respiration is the gas exchange aspect ventilation is breathing Mechanical process that depends on volume changes in the thoracic cavity By moving the diaphragm the pressure in the cavity changes The lower the volume the higher the pressure pressure volume inversely related Breathing or pulmonary ventilation consists of 2 phases o Inspiration air flows into lungs inhalation diaphragm Diaphragm contracts moves down Ribs elevated sternum expands as external intercostals contract o Expiration gases exit the lungs exhalation abdominal muscle Abdomen contracts during expiration Diaphragm relaxes move up and the rib cage descends due to gravity Thoracic cavity volume decreases Lungs recoil passively and intrapulmonary volume decreases Ppul rises about Patm 1mm causing air to leave the lungs hence why expiration gas flows out of the lungs until Ppul is zero 0 During normal quiet inhalation diaphragm and external intercostals contract During labored inhalation sternocleidomastoid scalenes and pectoralis minor also contract During normal exhalation the diaphragm and external intercostals relax During forceful exhalation abdominal and internal intercostal muscles contract Pressure relationships in the thoracic cavity Respiratory pressure is measured relative to atmospheric pressure Atmospheric pressure 760mm at sea level Atmospheric pressure pressure exerted by the air surrounding the body o Negative respiratory pressure less than atmospheric pressure Leads to inhalation so that air can go from high pressure outside the body to low pressure inside the body o Positive respiratory pressure greater than atmospheric pressure Leads to exhalation so that the air can go from high pressure inside the body to low pressure outside the body Ppul and Pip o Ppul intrapulmonary pressure pul pulmonary o Pip intrapleural pressure o Ppul and Pip fluctuate with the phases of breathing o Ppul always will eventually equalize with Patm o Pip is always less than Ppul and Patm If the pressure inside falls air flows in inhalation o Volume increases o Must have a positive difference of 3 mm compared to Patm in order to exhale Ex outside 760 mm so inside 763 mm Two forces act to pull lungs away from the thoracic wall promoting lung collapse o Elasticity of the lungs causes them to assume smallest possible size o Surface tension of alveolar fluid draws alveoli to their smallest size possible o Lung collapse Caused by equalization of the Pip with the Ppul Transpulmonary pressure keeps the airways open Transpulmonary pressure different between the intrapulmonary and intrapleural pressures Ppul Pip Opposing force elasticity of the chest wall pulls the thorax outward to enlarge the lungs Physical Factors Influencing Pulmonary Ventilation Airway resistance o Airflow is directly related to the difference in pressure o Airflow is inversely related to the tube resistance diameter The smaller the diameter the larger the resistance Can not change the diameter of big tubes with cartilage Can change the diameter of smaller tubes because they have smooth muscle Bronchial dilation o As airway resistance rises breathing becomes more strenuous o Constricted or obstructed bronchioles can prevent life sustaining ventilation and can occur during acute asthma attacks which stops ventilation Friction major non elastic source of resistance to airflow F P R o F flow o P pressure o R resistance o The amount of gas flowing into and out of the alveoli is directly proportional to the P P the pressure gradient between the atmosphere and alveoli Greatest resistance medium sized bronchi Amount of gas flowing into and out of the alveoli is directly proportional to the pressure gradient between the atmosphere and the alveoli Know difference in images of normal airway one with Asthma inflammation or Bronchoconstriction Epinephrine release via the Sympathetic nervous system dilates makes bigger bronchioles and reduces air resistance PNS activity increases air resistance Dead space and
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