Flashcards
Gas Exchange III - Mechanism of Ventilation 2
Cards in this deck (37)
- 1How do air molecules move? (2)Bulk flow and diffusion
- 2What happens when you move down the bronchiole tree?The trans cross-sectional area of the lungs increases
- 3What airway generation do the alveoli occur?Gen. 17
- 4How 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 - 5How does the movement of gas molecules occur in the conducting zone?As resistance is high in the conducting zone, air molecules have to move via bulk flow (convection)
All gas molecules moving in the same direction via a pressure gradient - 6How does the movement of gas molecules occur in the respiratory zone?CO2 and O2 diffuse independently from one another as resistance is negligible
diffusion - 7Describe laminar flow (3)Slow flow rate
parallel stream lines
molecules near edges of tube travel slower than those in the middle due to friction - 8What is Poiseuille's Law?V=Pπr4/8ƞl
p=pressure gradient
r=radius of airway
l=length of airway
ƞ=viscosity of subtance - 9Re-arrange Poiseuille's law to show the effect of reducing the radius of the airwayR=8ƞl/πr4
R∝1/r4
So if radius is halved, resistance increases by x16 - 10Describe turbulent flow (3)High flow rate
disorganised stream lines
net movement is still forward, occurs with asthma/exercise - 11Describe transitional flow (3)Intermediate flow rate
eddy currents at the branches, flow here is static.
Diagram - 12Where does majority of airway resistance occur?conducting airways
- 13What effect does ^ lung volume have on Raw?Raw decreases
- 14What effect does radial traction have?Decreases resistance
- 15How does radial traction occur?Lungs expand
Connective tissue pulls on bronchiole. - 16Why does this decrease Raw?Diameter of bronchioles increase
- 17Conditions leading to Dynamic Compressionlow lung volume
OR
intrathoracic pressure>alveolar pressure - 18When does Dynamic Compression occur?In forced expiration,
large transient pressure gradients created to force air out of lungs. - 19Type of airflow through constricted airwaysTurbulent
- 20If intrathoracic p > atmospheric p then:resistance increases enormously, airway may collapse under high pressure
- 21What type of change in bronchial smooth muscle tone produces which effect on RAW?Bronchioconstriction - increases RAW
Bronchiodilation - decreases RAW - 22What are the causes of bronchioconstriction? (4)1. Vagal stimulation
2. Fall in PCO2
3. Irritants inducing reflex constriction
4. Asthma - 23What stimulates bronchiodilation? (2)1. Circulating catecholamines - autonomic
2. Sympathetic agents (B2 agonists) - 24What is the effect of inflammation on RAW?Raw increases
- 25How does inflammation cause this change in RAW?External walls stay the same diameter whilst internal get smaller.
- 26Draw a diagram showing how increased airway resistance increases the work of breathingExpiration line passing through positive axis on the graph
- 27Why does expiration have to be active?As accessory muscles must contract to force air out
- 28What is elastic recoil determined by?Elastic properties of the lung tissues
Surface tension of the alveoli - 29What sort of fibres are found in alveolar walls and around vessels and bronchi?Elastin and collagen fibres
- 30What is the function of these fibres?Form network to allow distension under P
Recovers geometry when P is released - 31How does the fluid lining alveoli facilitate gas exchange?Decreases surface tension of water so O2 can dissolve in fluid, increases rate of diffusion.
- 32What is "pulmonary surfactant"A phospholipoprotein secreted from Type II alveolar cells
- 33What are the mechanical functions of surface? (2)Compresses alveoli to its spherical shape
Surface tension causes alveoli to recoil when pressure is released - 34What problems can arise because of this high attraction force?Transudation - drawing of ISF into alveoli
- 35What 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 - 36Where is pulmonary surfactant found?In all air-breathing animals and in the swim bladder of some fish.
- 37Under what conditions is compliance reduced? (2)When elasticity is impaired
When surface tension is increased (reducing production of surfactant.)
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- User has deleted their subject information Flashcards on Gas Exchange III - Mechanism of Ventilation 2, created by Deleted user on 19/04/2018.
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- Created by J yadonknow · Dec 22, 2017
- Copied by J yadonknow · Apr 19, 2018
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