Alveolar Ducts and Alveoli (Nursing)

by Rhonda Lawes, PhD, RN

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    00:00 Now these alveolar ducts, they are sacs that are surrounded by the alveolar ducts. So, they look like kind of like grape-like clusters and about 100 alveolar sacs are attached to the end of the ducts. This is the acinar region. Okay. So, how many clusters do we have? You've got clusters of 100 alveolar sacs and they're attached to the ends of the ducts. That's why we can have that much surface area in there because it's the way your lungs are designed. Now, each one of those sacs contains 20-30 alveoli. Okay, so you got that breakdown. I'd love for you to pause and just kind of sketch that out on the side for yourself. What do we have a hundred of? What do we have 20-30 of? ___ a solid frame of reference how the alveolar ducts and the alveoli are related. Okay, let's look at the alveoli. These are tiny but mighty little structures what they can do. This is where the gas exchange happens, now the alveoli are made of thin-walled parenchymal cells. When I say thin wall, it doesn't get any thinner. Typically, it's just 1 cell thick. Okay, that seems they'd be really fragile. Wouldn't they? Yes and they are.

    01:27 That's why when they fill with fluid or infection or they get hyperinflated, that's why it's so difficult for a patient to breathe when one of those things occurs because these are thin-walled structures because they've got exchange going across them with the capillaries that are also pretty permeable. So there's a reason alveoli are thin walled, it's because of their function and the role. So being 1 cell thick, they are just like these little tiny bubbles within the sacs. So alveoli are in direct contact with those capillaries, remember they're just 1 cell thick in the circulatory system of the capillaries so we've got alveoli, one-celled, very thin, relatively fragile, we've got a lot of them but they come in direct contact with the capillaries which also have a permeable membrane. That allows the blood flow to drop off the waste, the carbon dioxide, and pick up the oxygen and deliver it back to the tissues. Because the gas exchange, we've got it there, you can see where we have an idea of the blue being the unoxygenated blood what it turns into, the reddish color more, that means we've picked up the oxygen. Because oxygen diffuses from the alveoli into the blood and that's how it gets distributed to the rest of the body. So, CO₂ will diffuse from the blood into the alveoli to be exhaled and it will pick up the oxygen and take it all the way up. So I know we've said it repeatedly, but what is the unique job of the alveoli that doesn't happen anywhere else in the respiratory tract? Right, gas exchange. It happens by diffusion, it happens because the alveoli are very thin walled, pretty delicate. They right up against the capillaries which also have very permeable membranes and by diffusion CO₂ goes back into the alveoli to be exhaled out and oxygen goes into the capillary beds to be delivered to the tissues.

    About the Lecture

    The lecture Alveolar Ducts and Alveoli (Nursing) by Rhonda Lawes, PhD, RN is from the course Review: Anatomy and Physiology of the Respiratory System (Nursing).

    Included Quiz Questions

    1. Capillaries
    2. Alveolar ducts
    3. Arteries
    4. Heart
    1. Alveoli
    2. Venous tissue
    3. Elastic fibers
    4. Capillaries

    Author of lecture Alveolar Ducts and Alveoli (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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