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Diaphragm: Functions (Nursing)

by Rhonda Lawes

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      Slides Nursing Respiratory System Diaphragm Phrenic Nerve.pdf
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    00:00 Hi, welcome to our respiratory video series. Now on this one, we're going to take a look at the diaphragm and the phrenic nerve. Now, these 2 don't get a lot of loving or recognition but they're vitally important. Let me help you understand why. Now, first of all, take a deep breath in and then breathe out. Okay, let me tell you what you just did. See, when you breathe in the muscles of the chest help you breathe by changing the size of the thoracic cavity. Well that makes sense because when I breathe in, everything gets a little bigger, right, as it fills in.

    00:38 Because as you breathe in or inhale, your chest rises and that thoracic cavity expands and it increases the negative pressure which allows you to suck in the air to your lungs. Now, when you breathe out, it doesn't take as much effort. Just think of everything kind of relaxing because when you breathe out or exhale, your chest just kind of falls back in the thoracic cavity, empties out, and it becomes smaller again or back to the starting size. So the main driver or muscle of breathing is the diaphragm. So the diaphragm is a sheet of skeletal muscle, use it even when you're asleep because it has to contract and relax, it contract and relax in order for you to breathe all day and all night. So luckily it's made of skeletal muscle and that's one we don't control or have to think about. So how does sniffing impact the diaphragm? Well, the best way to figure that out is for you to do it. So try this, (sniff, sniff). Okay, pay attention to what happens to your diaphragm when you do that with me (sniff, sniff). Yeah, isn't that cool? Because the sniffing maneuver activates the diaphragm and it exaggerates its movement. So, I don't guarantee or recommend that you go around doing that, but it does help you start to get it filled for what the diaphragm does. Now we can actually do a sniff test. It's a diaphragm fluoroscopy and it can be done with fluoroscopy and it helps us kind of take a look at what the diaphragm is doing and its ability to move up and down. Little more science than the sniff test but it does give us some helpful information if the patient is having problems with their diaphragm movement. Now, we look at the diaphragm, it's a dome-shaped, alright, so it's a dome-shaped muscle at rest. Now the diaphragm is what separates the thoracic cavity from the abdominal cavity so it's the dividing line. Now, the superior surface or the top of the diaphragm is convex, it's kind of dome-shaped and it's the floor of the thoracic cavity. Now the inferior surface is concave. It creates kind of a curved roof of the abdominal cavity. Now the liver is next to the diaphragm on the patient's right and the stomach is more on the left. So I want you to kind of get a feeling for the landmarks of the diaphragm. What shape is it? What's on the right side? What's on the left side? So you kind of get a feel of this fantastic muscle as we're walking through it. Now we have this very simple movement for you here, but I want you to take a look at that. So, you can see the diaphragm is the muscle, that line right beneath the lungs. Now, as it pulls down, that's the diaphragm contracting. What happens to the lungs when that muscle moves down? Okay, you see the lungs get bigger. That's because when the diaphragm pulls down, it creates negative pressure and that's what sucks the air into the thoracic cavity. The diaphragm contracts and it relaxes and that's what changes the volume of the pleural cavity. So, it contracts and relaxes, contracts and relaxes, contracts and relaxes. That's what that muscle does, helps with the negative pressure that it creates and that's what allows me to fill my lungs with air. Because when the diaphragm contracts or it flattens, it creates a larger volume in the pleural cavity, the negative pressure and that's what draws in the air. Okay, so it's a simple muscle but has a really vital function to life. Now let's talk about these intercostal muscles. You have 3 sets, so you have the innermost, the internal, and the external. Now, I've got a graphic there for you so just take a look at those as we're talking through these key points. Now the intercostals are ones that help breathing but the other ones help change the dimensions of the rib cage. When you breathe in, right, your rib cage expands. These are the muscles that are responsible for that.

    04:50 When I take a breath in, there are 11 pairs of external intercostal muscles and they're the ones that help raise the rib cage and make the cavity bigger. Now when I exhale, there are 11 pairs of internal intercostal muscles. They help draw the ribs back together to constrict the rib cage. So, 11 pairs of, right, external intercostals, those are the ones that help me take a breath in then there are 11 pairs of internal intercostals muscles and that helps bring the rib cage back in. So the diaphragm changes the pressure, the intercostal muscles are very involved in helping that rib cage raise and become larger in the cavity.


    About the Lecture

    The lecture Diaphragm: Functions (Nursing) by Rhonda Lawes is from the course Review: Anatomy and Physiology of the Respiratory System (Nursing).


    Included Quiz Questions

    1. Negative pressure increases, "sucking in" air to your lungs.
    2. Negative pressure decreases, "sucking in" air to your lungs.
    3. Negative pressure increases, "pushing out" air of your lungs.
    4. Negative pressure decreases, "pushing out" air of your lungs.
    1. Diaphragm
    2. Lungs
    3. Heart
    4. Excess oxygen
    1. 11 pairs of internal and external intercostal muscles
    2. 6 pairs of internal and external intercostal muscles
    3. 12 pairs of internal and external intercostal muscles
    4. 23 pairs of internal and external intercostal muscles

    Author of lecture Diaphragm: Functions (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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