11806085
Description
Flashcards by J yadonknow, updated more than 1 year ago
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Created by J yadonknow
almost 7 years ago
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| Question | Answer |
| How do air molecules move? (2) | Bulk flow and diffusion |
| What happens when you move down the bronchiole tree? | The trans cross-sectional area of the lungs increases |
| What airway generation do the alveoli occur? | Gen. 17 |
| How does the total trans-sectional area differ in the different zones of the respiratory tract? | Total trans-sectional area in conducting zone is small so resistance is high Total trans-sectional area in respiratory zone is high so resistance is negligible |
| How does the movement of gas molecules occur in the conducting zone? | Bulk flow due to high R |
| How does the movement of gas molecules occur in the respiratory zone? | R negligible CO2 and O2 diffuse independently |
| Describe laminar flow (3) | Slow flow rate parallel stream lines molecules near edges of tube travel slower than those in the middle due to friction |
| What is Poiseuille's Law? | V=Pπr4/8ƞl p=pressure gradient r=radius of airway l=length of airway ƞ=viscosity of subtance |
| Re-arrange Poiseuille's law to show the effect of reducing the radius of the airway | R=8ƞl/πr4 R∝1/r4 So if radius is halved, resistance increases by x16 |
| Describe turbulent flow (3) | High flow rate disorganised stream lines net movement is still forward, occurs with asthma/exercise |
| Describe transitional flow (3) | Intermediate flow rate eddy currents at the branches, flow here is static. Diagram |
| Where does majority of airway resistance occur? | conducting airways |
| What effect does ^ lung volume have on Raw? | Raw decreases |
| What effect does radial traction have? | Decreases resistance |
| How does radial traction occur? | Lungs expand Connective tissue pulls on bronchiole. |
| Why does this decrease Raw? | Diameter of bronchioles increase |
| Conditions leading to Dynamic Compression | low lung volume OR intrathoracic pressure>alveolar pressure |
| When does Dynamic Compression occur? | In forced expiration, large transient pressure gradients created to force air out of lungs. |
| Type of airflow through constricted airways | Turbulent |
| If intrathoracic p > atmospheric p then: | resistance increases enormously, airway may collapse under high pressure |
| What type of change in bronchial smooth muscle tone produces which effect on RAW? | Bronchioconstriction - increases RAW Bronchiodilation - decreases RAW |
| What are the causes of bronchioconstriction? (4) | 1. Vagal stimulation 2. Fall in PCO2 3. Irritants inducing reflex constriction 4. Asthma |
| What stimulates bronchiodilation? (2) | 1. Circulating catecholamines - autonomic 2. Sympathetic agents (B2 agonists) |
| What is the effect of inflammation on RAW? | Raw increases |
| How does inflammation cause this change in RAW? | External walls stay the same diameter whilst internal get smaller. |
| Draw a diagram showing how increased airway resistance increases the work of breathing | Expiration line passing through positive axis on the graph |
| Why does expiration have to be active? | As accessory muscles must contract to force air out |
| What is elastic recoil determined by? | Elastic properties of the lung tissues Surface tension of the alveoli |
| What sort of fibres are found in alveolar walls and around vessels and bronchi? | Elastin and collagen fibres |
| What is the function of these fibres? | Form network to allow distension under P Recovers geometry when P is released |
| How does the fluid lining alveoli facilitate gas exchange? | Decreases surface tension of water so O2 can dissolve in fluid, increases rate of diffusion. |
| What is "pulmonary surfactant" | A phospholipoprotein secreted from Type II alveolar cells |
| What are the mechanical functions of surface? (2) | Compresses alveoli to its spherical shape Surface tension causes alveoli to recoil when pressure is released |
| What problems can arise because of this high attraction force? | Transudation - drawing of ISF into alveoli |
| What are the roles of the pulmonary surfactant? | Lowers surface tension in the liquid layer of alveoli Prevents alveolar collapse at low pressure, which is essential for maintaining the FRC |
| Where is pulmonary surfactant found? | In all air-breathing animals and in the swim bladder of some fish. |
| Under what conditions is compliance reduced? (2) | When elasticity is impaired When surface tension is increased (reducing production of surfactant.) |
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