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33 Cards in this Set
- Front
- Back
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What are the four lung volumes? |
Inspiratory reserve volume Tidal volume expiratory reserve volume Residual volume |
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Tidal Volume (VT) |
Amount of air breathed in and out during one normal breath (one normal respiratory cycle)
~15 mL/kg |
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Residual Volume (RV) |
Volume of air that remains in the lungs after a complete and forceful expiration. Not possible to breathe it out |
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Inspiratory Reserve Volume |
Amount of air that you can inspire beyond what you breathe in during a normal breath. -Can access this when you exercise th increase how much you can breathe |
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Expiratory Reserve Volume |
Amount of air you can expire beyond what you breathe out during a normal breathe. - extra amount you breathe out during a normal breathe |
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Vital Capacity |
Maximum amount of air that can be inspired after the maximum amount of air has been expired (most you can breathe in and out with maximal effort) |
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Total Lung Capacity |
Vital capacity + residual volume |
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Functional Residual Capacity |
Residual Volume + Expiratory Reserve Volume - amount of air in lung after a normal expiration -lung volume that occurs when the chest wall and lung in equilibrium -If you stopped breathing you would still have this amount of air to participate in gas exchange. |
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Energy used during breathing |
1. Contraction of muscles expands thorax. 2. Needs to overcome elastic recoil that would contract the lungs. 3. Needs to overcome resistance to air flow through respiratory system. |
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Compliance |
Measure of the distensibility of the lung. Determined by measuring the change in volume as a result of a change in pressure. -In mid range pressure, compliance is high -At high and low pressure compliance is low |
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Surface Tension |
Attractive forces between atoms or molecules. Water molecules pull on each other |
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Alveolar Surface Tension |
Laplace's Law: P =2T/r P = pressure inside alveolus T = tension on inner surface r = internal radius of alveolus -Smaller the alveolus in, the higher the pressure you need to overcome. |
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Inspiratory capacity |
Inspiratory reserve volume + tidal volume |
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Laplace's law |
P = 2T/r P = pressure inside alveolus >works to expand T = tension on inner surface > works to contract alveolus r = internal radius of alveolus |
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At a given surface tension, would small or large alveoli have higher internal pressure? What does this mean? |
Small alveoli will have a higher internal pressure. As a result, they would always empty into larger alveoli which is not good. Would require more energy to breathe, so surfactant comes in. |
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What is surfactant? |
Substance that accumulates at the surface of a fluid to reduce tension. |
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What is pulmonary surfactant? |
Lipoprotein complex (70% lipid, 30% protein). -Synthesized by type II alveolar epithelial cells (secretory cells) |
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What happens at the end of expiration? |
-Alveolus is at its smallest size (small r) -Surfactant becomes more concentrated on surface of alveolus which reduces surface tension, counteracting effects of small radius. -stabilizes alveolus when small so doesn't just dump into larger
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What happens at the end of inspiration? |
-Alveolus is at its largest size (large r) -Surfactant less concentrated so surface tension (T) increases -This provides some of the recoil necessary for making expiration passive |
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Poiseuille's Law |
Resistance = 8nl/πr^4 n = viscosity of fluid or gas l = length of tube r = radius of tube
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What is the effect of diameter of airway resistance? |
A very small change in diameter can have a huge change in resistance ( over r^4). If the radius is halved, the force must be increased 16x to maintain flow. |
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What is the effect of length on airway resistance? |
If the length is doubled, resistance will double and need to double the force to maintain constant flow. Not as big an effect as radius on resistance. |
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Where is the highest resistance to airflow in the respiratory system? |
Around the 4th or 5th bronchioles. Tubes are splitting but still have a large tube splitting so high turbulence. |
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Why does airway resistance go down if airways get progressively smaller? |
Diameter of each tube gets smaller, but the total diameter increases exponentially. |
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3 gas laws |
Volume = constant/pressure Volume = constant x temperature Dissolved amount of gas = pressure x solubility coeficient |
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Partial pressure |
The pressure exerted by a specific gas when it is in a mixture of gases (its part of the total pressure)
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Dalton's Law |
The pressure of one gas is independent of the pressures exerted by the other gases. Sum of all the individual pressures is equal to the total gas pressure. denoted by P |
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How do you find the partial pressure of a gas? |
P of a gas is found by multiplying its fractional concentration (%) by the total gas pressure e.g., PO2 = 0.21 x 760 mmHg = 160mmHg |
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Pa refers to... |
Arterial pressure of a gas - the amount dissolved in plasma
Does not change until it gets to capillaries so an arterial gas will tell you what is in the lungs. |
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Pv refers to... |
Venous pressure of a gas - amount dissolved in plasma
If you want a venous sample that gives info from whole body take from pulmonary artery |
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PA refers to... |
Alveolar pressure of a gas - air in the lung |
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Fick's law |
Vgas =A x D x (P1 –P2)/T
A = surface area of membrane D = diffusion coeeficient for the gas (solubility and size) P1 and P2 = partial pressures on each side of the membrane T = thickness of membrane |
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What conditions favour optimal gas exchange? |
Large surface area Fast diffusion coefficient Large difference between 2 partial pressures Thin membranes |
