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Partial Pressure Gradient and Respiratory Membranes – External Respiration (Nursing)

by Jasmine Clark

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    00:01 So external respiration or pulmonary gas exchange is going to involve the exchange of oxygen and carbon dioxide across our respiratory membranes.

    00:12 This exchange is going to be influenced by several things.

    00:16 First, the partial pressure gradients of each of these gases as the gas solubilities.

    00:23 Second, the thickness and the surface area of our respiratory membranes, and finally a phenomenon known as ventilation and perfusion coupling which is going to match alveolar ventilation with pulmonary blood perfusion.

    00:39 So taking a closer look at these influences and starting with partial pressure, recall that there is a steep partial pressure gradient for oxygen that exists between the blood and the lungs.

    00:52 Your venous blood are the blood returning from your tissues has a partial pressure of oxygen of 40 millimeters of mercury.

    01:02 This is compared to the alveolar partial pressure of oxygen which is much higher at a hundred and four millimeters of mercury.

    01:10 Because of this, oxygen is going to flow down its concentration gradient out of the alveoli and into the venous blood.

    01:20 We reach an equilibrium between these two across the respiratory membrane at about .25 or a quarter of a second.

    01:29 However, it takes our red blood cells about three-quarters of a second to travel from the start to the end of a pulmonary capillary.

    01:39 Because of this delay and the travel of the red blood cells.

    01:43 It allows for an adequate oxygenation of the blood cells because of this like slowing our bottleneck.

    01:53 So the partial pressure gradient for carbon dioxide is a less steep than that of oxygen.

    01:59 In the venous blood or the blood returning from the tissues.

    02:03 The partial pressure of carbon dioxide is 45 millimeters of mercury.

    02:08 And the alveoli, this is going to be a little bit lower at 40 millimeters of mercury.

    02:15 Although this gradient is not as steep as that of oxygen.

    02:19 The carbon dioxide is still going to diffuse out an equal amounts.

    02:24 And the reason why is because carbon dioxide is much more soluble and plasma than oxygen and is therefore held on to a little bit more so it doesn't require a steep of a gradient in order for it to move out.

    02:40 So another factor that is going to influence our external respiration is the thickness and the surface area of our respiratory membranes.

    02:49 So recall that our respiratory membranes are extremely thin and there are only about a half to one millimeter thick.

    02:57 This allows for efficient diffusion across this membrane into and out of the alveoli.

    03:05 Also the alveoli have a huge surface area.

    03:09 In fact, the surface area of all of our alveoli put together is more than 40 times the surface area of all of your skin.


    About the Lecture

    The lecture Partial Pressure Gradient and Respiratory Membranes – External Respiration (Nursing) by Jasmine Clark is from the course Respiratory System – Physiology (Nursing).


    Included Quiz Questions

    1. Alveoli
    2. Pulmonary veins
    3. Pulmonary arteries
    4. Systemic veins
    5. Systemic arteries
    1. Partial pressure gradients and gas solubilities
    2. Thickness and surface area of respiratory membrane
    3. Ventilation-perfusion coupling
    4. Matching of alveolar ventilation with pulmonary blood perfusion
    5. Differences in blood types

    Author of lecture Partial Pressure Gradient and Respiratory Membranes – External Respiration (Nursing)

     Jasmine Clark

    Jasmine Clark


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