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062 Pressure Changes during Breathing

Breathing is one of the most common things we do everyday to a point that it becomes unnoticed. Wouldn’t it be great to learn what happens behind this process? What exactly happens when we breathe air in and out of our body? Watch this video as Leslie teaches once again in such an easy way to make it all easy for us to understand this concept.

Have fun!

Transcript of Todays Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel. In this episode, Episode 62, I’m going to be talking about pressure changes that happen during breathing. That’s what we’re going to talk about. Let’s just get right into it.

We’ve been talking about the respiratory system. We have been talking about the fact that you are breathing in. As air comes in, so let’s say the air is coming through here and then, it eventually ends up in the lungs. In the lungs, we can see here we have the alveoli. As the air comes in, that air can then give oxygen to the blood and it can take carbon dioxide and bring that into the cavity here and then, when you breathe out, of course, that air is going to go through the mouth and through the nose, depending on how you’re breathing and that’s going to push the air outside.

What we’re going to talk about is how this process of breathing actually happens and the pressure changes that are involved.

Here we have the two lungs. What I’m going to do is I’m going to draw an additional part here because this diagram is kind of simplified so, we’re just going to add a little more. We’re going to close this off and we are going to close that part off. And then, I’m going to give some names.

This entire section that we’re dealing with, that is called the thoracic cavity. In the thoracic cavity, we have this space right here. That space is called the pleural cavity. Then, we have one more cavity and that’s inside the lungs. We’re going to call that the pulmonary cavity. Another thing that we need to label here, this here is a muscle and that muscle we call the diaphragm. Beneath here we have the abdominal cavity but, we’re not going to talk too much about that. Actually, let me still label it here because we are going to mention it. Abdominal cavity.

What we’re going to talk about is what happens during breathing. Over here we’re looking at muscles and here you can see we have this group of muscles here and that is called the external intercostals. You can see it diagonally going here. Then, here we have the internal intercostals muscles. So, we’re going to talk about the things that happen during breathing and we’re going to mention what roles those play also.

When I’m breathing in, I’m taking a breath. I just breathe in. There are a number of things that are happening.

First thing is we have the diaphragm here and the diaphragm contracts. When the diaphragm contracts, that moves down. It kind of moves down here. Then, we have the external intercostals. When they contract, that moves the rib cage up. So the diaphragm is contracting; the external intercostals are contracting; this moves down, the external intercostals move the rib cage up and the overall effect is that we’re increasing the space of the thoracic cavity. So, we’re increasing the size of the thoracic cavity. When you increase the size, that is going to cause a decrease in pressure in the thoracic cavity. Of course, since you’re increasing the size and you’re pushing down here with the diaphragm, it’s increasing the pressure in the abdominal cavity, decreasing the pressure in the thoracic cavity. Of course then, that’s going to cause a reduction in pressure of the pleural cavity. When the pressure is reduced in the pleural cavity, that then becomes lower than the pressure inside the lungs in the pulmonary cavity.

Once again, diaphragm contracts, external intercostals contract. That expands the thoracic cavity, decreasing the pressure in the pleural cavity. If we have a lower pressure in here than in the lungs, what is going to happen to the lungs? Of course, greater pressure inside, lower pressure on the outside, the lungs are going to expand. As the lungs expand, now you have more space in here, that’s going to decrease the pressure in the pulmonary cavity, relative to the pressure of the atmosphere. That is going to cause air to move from higher pressure to lower pressure and the air is going to go in and, of course, go into the lungs.

Let’s review that again: Diaphragm contracts, external intercostals contract that expands the thoracic cavity, decreasing the pressure in the pleural cavity. Because that’s going to be now lower than the pulmonary cavity, that’s going to cause the lungs to expand causing a reduction in pressure in the pulmonary cavity. That’s going to cause air to move from the atmosphere into the lungs. And, we have just accomplished breathing in.

During normal breathing, what then happens when it’s time to, not inspire, but expire, so, exhale. The diaphragm and the external intercostal muscles are going to relax. Since we had a buildup in pressure here, when the diaphragm contracted, the abdominal cavity is then going to push against the thoracic cavity increasing the pressure in the pleural cavity, increasing the pressure in the pulmonary cavity causing air to leave. So, it’s the exact opposite.

First, we’re decreasing the pressure by expanding then, now we are increasing the pressure by making the cavity smaller, pushing the air out. That’s during normal breathing.

When you are breathing more intense and it’s more of a forced breathing situation, it’s very similar to what we just described except that there are other muscles involved. So, for inspiration, the diaphragm is going to contract, external intercostals are going to contract and also some neck muscles and we’re going to get air coming in. It’s a stronger contraction. So, that’s going to bring more air in because you’re reducing the pressure even more.

Then, when you’re breathing out, you’re not just relaxing the diaphragm but you’re also bringing in the internal intercostals muscles and those are going to contract and when those contract, the rib cage moves down, thoracic cavity gets smaller, faster of course, and that’s going to increase pressure faster, and cause more air to be pushed out into the atmosphere.

Overall, you’re breathing in because you’re decreasing the pressure on the inside, you’re breathing out because you’re increasing the pressure on the inside.

That’s pretty much all for this episode. As usual, if you want to find more of these videos and other resources I’d like to invite you to visit the website at Interactive-Biology.com. That’s it for this video and I’ll see you on the next one.

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Leslie Samuel is the creator of Interactive Biology. His mission is to use this site to Make Biology fun for people all over the world.

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Leave An AWESOME Comment

89 Responses to “062 Pressure Changes during Breathing”

  1. kiddlatoya July 1, 2011 at 12:52 am #

    love your videos and look forward to seeing them

  2. kiddlatoya July 1, 2011 at 4:52 am #

    love your videos and look forward to seeing them

  3. InteractiveBiology July 1, 2011 at 8:54 am #

    @kiddlatoya Thanks, I look forward to making MANY more :)

  4. InteractiveBiology July 1, 2011 at 8:54 am #

    Thanks, I look forward to making MANY more :)

  5. InteractiveBiology July 1, 2011 at 12:54 pm #

    Thanks, I look forward to making MANY more :)

  6. RS August 20, 2011 at 6:55 pm #

    Is it possible for you to make a video topic that just covers ‘ACID BASE’. For instance, Metabolic alkalosis, Respiratory Alkalosis? You are doing a wonderful job with these videos. It will be nice of you if you please cover the acid base topic in the Respiratory system. Thanks

    • Lrsamuel August 20, 2011 at 8:49 pm #

      Thanks for your comment. In terms of the videos, I make them as I need them for the classes I’m going to be teaching. If that ever comes up, I’ll make a video about it.

      All the best!

  7. oneaware September 1, 2011 at 3:28 pm #

    Leslie, I found your website and it’s been a tremendous help for me in nursing school. It is an excellent review of basic physiology that is actually understandable. God bless.

  8. oneaware September 1, 2011 at 7:28 pm #

    Leslie, I found your website and it’s been a tremendous help for me in nursing school. It is an excellent review of basic physiology that is actually understandable. God bless.

  9. InteractiveBiology September 1, 2011 at 9:07 pm #

    @oneaware Glad to know it’s helping. All the best!

  10. InteractiveBiology September 1, 2011 at 9:07 pm #

    Glad to know it’s helping. All the best!

  11. InteractiveBiology September 2, 2011 at 1:07 am #

    Glad to know it’s helping. All the best!

  12. youhaventgotaprayer November 5, 2011 at 6:13 am #

    very educational, thank you

  13. youhaventgotaprayer November 5, 2011 at 10:13 am #

    very educational, thank you

  14. InteractiveBiology November 7, 2011 at 8:41 am #

    @youhaventgotaprayer You’re very much welcome. Do stay tuned for more as Leslie plans to put up more Biology videos coming very soon.

  15. InteractiveBiology November 7, 2011 at 8:41 am #

    You’re very much welcome. Do stay tuned for more as Leslie plans to put up more Biology videos coming very soon.

  16. InteractiveBiology November 7, 2011 at 1:41 pm #

    You’re very much welcome. Do stay tuned for more as Leslie plans to put up more Biology videos coming very soon.

  17. zackboomer November 12, 2011 at 7:17 pm #

    Leslie is a great person

  18. zackboomer November 13, 2011 at 12:17 am #

    Leslie is a great person

  19. InteractiveBiology November 13, 2011 at 10:54 am #

    @zackboomer Yes, he is indeed! :)

  20. InteractiveBiology November 13, 2011 at 10:54 am #

    Yes, he is indeed! :)

  21. InteractiveBiology November 13, 2011 at 3:54 pm #

    Yes, he is indeed! :)

  22. yavneh911 November 29, 2011 at 2:28 pm #

    LOVING TO LEARN BC OF YOU

  23. yavneh911 November 29, 2011 at 7:28 pm #

    LOVING TO LEARN BC OF YOU

  24. InteractiveBiology November 29, 2011 at 7:45 pm #

    @yavneh911 Glad to know that. :) Leslie is indeed a great teacher! You can keep on learning more Biology stuff from our website. There will be more videos that will be uploaded so, please stay tuned!

  25. InteractiveBiology November 29, 2011 at 7:45 pm #

    Glad to know that. :) Leslie is indeed a great teacher! You can keep on learning more Biology stuff from our website. There will be more videos that will be uploaded so, please stay tuned!

  26. InteractiveBiology November 30, 2011 at 12:45 am #

    Glad to know that. :) Leslie is indeed a great teacher! You can keep on learning more Biology stuff from our website. There will be more videos that will be uploaded so, please stay tuned!

  27. jckpink7 December 11, 2011 at 10:56 am #

    thank you so much..i finally understand, you really know how to make things clear!!! thank you thank you

  28. jckpink7 December 11, 2011 at 3:56 pm #

    thank you so much..i finally understand, you really know how to make things clear!!! thank you thank you

  29. InteractiveBiology December 11, 2011 at 7:16 pm #

    @jckpink7 You’re welcome! We’re glad to know you’re finding value in them. Stay tuned! We have new Biology videos coming soon!

  30. InteractiveBiology December 11, 2011 at 7:16 pm #

    You’re welcome! We’re glad to know you’re finding value in them. Stay tuned! We have new Biology videos coming soon!

  31. InteractiveBiology December 12, 2011 at 12:16 am #

    You’re welcome! We’re glad to know you’re finding value in them. Stay tuned! We have new Biology videos coming soon!

  32. michaelc5876 February 3, 2012 at 1:05 pm #

    hello good sir, have you done anything on surface tension or compliance

  33. michaelc5876 February 3, 2012 at 1:05 pm #

    hello good sir, have you done anything on surface tension or compliance

  34. InteractiveBiology February 3, 2012 at 4:51 pm #

    @michaelc5876 Please refer to our website at Interactive Biology for a list of complete videos. Thank you so much! :)

  35. InteractiveBiology February 3, 2012 at 4:51 pm #

    Please refer to our website at Interactive Biology for a list of complete videos. Thank you so much! :)

  36. michaelc5876 February 3, 2012 at 6:05 pm #

    hello good sir, have you done anything on surface tension or compliance

  37. InteractiveBiology February 3, 2012 at 9:51 pm #

    Please refer to our website at Interactive Biology for a list of complete videos. Thank you so much! :)

  38. vj March 9, 2012 at 8:04 am #

    thank you so much …. is it possible for u make a video of alveoli mechanism…

    • Leslie Samuel March 11, 2012 at 11:59 pm #

      Hi Vj. Glad you are finding value in the videos. Unfortunately, I can no longer take requests for videos as I’m receiving more requests than I have time to do.

  39. bballplayaluva March 14, 2012 at 10:36 pm #

    you are heaven sent for real!!!!!!

  40. bballplayaluva March 15, 2012 at 2:36 am #

    you are heaven sent for real!!!!!!

  41. NBAfan1993 April 1, 2012 at 4:03 pm #

    Don’t the lungs collapse during inspiration? :S

  42. NBAfan1993 April 1, 2012 at 8:03 pm #

    Don’t the lungs collapse during inspiration? :S

  43. ARASH April 22, 2012 at 4:41 pm #

    YOU ARE REALLY DOING A GREAT JOB. GOD BLESS YOU…

  44. Misswannabnurse April 24, 2012 at 5:21 pm #

    Really helpful. Thanks!

  45. Misswannabnurse April 24, 2012 at 5:21 pm #

    Really helpful. Thanks!

  46. Misswannabnurse April 24, 2012 at 9:21 pm #

    Really helpful. Thanks!

  47. mohsenfahmy May 3, 2012 at 8:29 am #

    good work please keep on

  48. scaler27 May 19, 2012 at 12:17 pm #

    I quit smoking with Campral…Watch my youtube video Campral

  49. scaler27 May 19, 2012 at 12:17 pm #

    I quit smoking with Campral…Watch my youtube video Campral

  50. 4leafclover987 May 26, 2012 at 8:13 pm #

    Excellent demonstration! I wish you included alveolar pressures too, though.

  51. 4leafclover987 May 26, 2012 at 8:13 pm #

    Excellent demonstration! I wish you included alveolar pressures too, though.

  52. AGirlFromDownUnder May 28, 2012 at 1:30 pm #

    During inspiration, you breathe in and air enters your lungs, so they expand.

    There is always air inside your lungs, even when you breathe out as much as you can :)

  53. AGirlFromDownUnder May 28, 2012 at 1:30 pm #

    During inspiration, you breathe in and air enters your lungs, so they expand.

    There is always air inside your lungs, even when you breathe out as much as you can :)

  54. AGirlFromDownUnder May 28, 2012 at 1:37 pm #

    Ext. Intercostals actually move up AND outwards.
    Also, in forced inspiration (when you take a breath on purpose or are breathing hard), serratus anterior becomes involved as well as the sternocleomastoid, Scalene muscles and the laryngeal/pharyngeal muscles. These are not used at rest!
    In forced expiration, the abdominal muscles come into play (int./ext. obliques, transversus abdominus and rectus abdominus (‘Six-pack’ muscles).
    At rest, expiration is passive and occurs due to elastic recoil.

  55. AGirlFromDownUnder May 28, 2012 at 1:37 pm #

    Ext. Intercostals actually move up AND outwards.
    Also, in forced inspiration (when you take a breath on purpose or are breathing hard), serratus anterior becomes involved as well as the sternocleomastoid, Scalene muscles and the laryngeal/pharyngeal muscles. These are not used at rest!
    In forced expiration, the abdominal muscles come into play (int./ext. obliques, transversus abdominus and rectus abdominus (‘Six-pack’ muscles).
    At rest, expiration is passive and occurs due to elastic recoil.

  56. AGirlFromDownUnder May 28, 2012 at 1:37 pm #

    Ext. Intercostals actually move up AND outwards.
    Also, in forced inspiration (when you take a breath on purpose or are breathing hard), serratus anterior becomes involved as well as the sternocleomastoid, Scalene muscles and the laryngeal/pharyngeal muscles. These are not used at rest!
    In forced expiration, the abdominal muscles come into play (int./ext. obliques, transversus abdominus and rectus abdominus (‘Six-pack’ muscles).
    At rest, expiration is passive and occurs due to elastic recoil.

  57. scottseptember1992 June 2, 2012 at 7:40 pm #

    @InteractiveBiology

    This is a wonderfully thorough video. The mentioning of “Boyle’s Law” (which describes the INVERSE relationship between Pressure and Volume, like popping a boil) would further clarify the ventilation mechanism. To integrate this to the NS, the Central NS’s Brain Stem sending signals the Peripheral Nervous System’s Motor System’s efferent (going away from CNS) neurons towards the diaphragm and intercostal muscles and causing them to contract is how this is all “regulated.”

  58. scottseptember1992 June 2, 2012 at 7:40 pm #

    @InteractiveBiology

    This is a wonderfully thorough video. The mentioning of “Boyle’s Law” (which describes the INVERSE relationship between Pressure and Volume, like popping a boil) would further clarify the ventilation mechanism. To integrate this to the NS, the Central NS’s Brain Stem sending signals the Peripheral Nervous System’s Motor System’s efferent (going away from CNS) neurons towards the diaphragm and intercostal muscles and causing them to contract is how this is all “regulated.”

  59. Kyle Nez September 11, 2012 at 9:28 pm #

    Thank you so much… now i understand…

  60. iluv2color27 September 21, 2012 at 6:32 pm #

    you my friend do an excellent job at explaining … i now understand!!! lol thank you :)

  61. Alejandro Vaco October 14, 2012 at 10:22 pm #

    exelent work!!

  62. MrBalladur October 20, 2012 at 7:31 am #

    Thank you. Very helpful.

  63. Mallory Richards October 23, 2012 at 10:09 pm #

    This was really useful and helpful. I wish you had a video of ventilation-perfusion coupling. I have never watched a video from you that I don’t understand, and ventilation-perfusion coupling is hard.

  64. butabobotabu November 5, 2012 at 1:29 am #

    Your videos are really helpful. I always look for any videos that is related to the topic I work on before I start reading my lab manual.

  65. butabobotabu November 5, 2012 at 1:30 am #

    Also, could you please go into a little more details about how the decreasing pressure in the pleural cavity can affect the pressure inside the pulmonary cavity? Thanks a lot.

  66. emullen93 November 5, 2012 at 5:51 am #

    I swear im going to owe my freakin nursing degree to these damn videos lololol

  67. kelciclemmensen November 13, 2012 at 11:52 am #

    This was very informative. Thank you !!

  68. DeathNoteKiraluver November 18, 2012 at 7:07 pm #

    That helped so much!~ Thank you!~

  69. Daniel Adedara December 13, 2012 at 3:55 am #

    Is he Jamaican?

  70. Clar1787 January 17, 2013 at 4:22 am #

    awesome video!

  71. Michelle Davin January 23, 2013 at 11:44 pm #

    Enjoying expanding my knowledge and learning more and more Thank you !

  72. vanderley3 April 1, 2013 at 11:10 pm #

    Excellent explanation thank you!

  73. Anna Craft O'Neal April 2, 2013 at 9:41 pm #

    just a minor clarification, though I LOVE your videos, keep up the good work! During expiration, the pleural cavity pressure is still LESS than the pressure in the lungs (intrapulmonary pressure). During inspiration, it is the relative pressure of pleural to pulmonary that causes the influx of air as well as the relative difference of intrapulmonary to atmospheric (greater, at least -1mmHg), pulling air into the lungs. Air flows down gradient until Ppul = Patm. The pressure always wants to be =

  74. Brett Cochrane April 9, 2013 at 3:49 pm #

    love this guy

  75. Peter Finnegan May 15, 2013 at 9:05 am #

    Excellent!

  76. Obaid Alhamid May 17, 2013 at 12:44 pm #

    I need your brain

  77. Navin Oorjitham May 18, 2013 at 4:06 pm #

    Awesome. Very concise. Thank you!

  78. Charlotte Morris May 28, 2013 at 6:27 am #

    These videos are saving my life, well, my degree XD

  79. Sharafath Hussain June 2, 2013 at 3:00 am #

    Thanks bro very helpful …

  80. Angela Lopez June 20, 2013 at 1:12 pm #

    Wonderful video! super helpful!

  81. sheenamae09 July 30, 2013 at 2:31 am #

    my finals is two days from now!!! Argh nursing !!!! LOL

  82. Natalie Whitney September 30, 2013 at 2:07 pm #

    Thank you!

  83. KaYuk Yuen October 4, 2013 at 6:58 am #

    Really helpful! THANK YOU!

  84. Chris H October 20, 2013 at 12:44 pm #

    Very useful, thank you. Despite understanding Boyle’s law, I was having a hard time orienting myself on the movement of the diaphragm, intercostals, and lungs. Awesome job.

  85. Fityan Guitarist October 26, 2013 at 12:38 am #

    Thank you soooo much .

  86. Fityan Guitarist October 26, 2013 at 12:38 am #

    Thank you soooo much .

  87. Bo Mhayhay October 29, 2013 at 3:09 pm #

    thank U a lot