Physiologic Mechanisms of Breathing and Gas Exchange (Nursing)

00:01 So now let's talk about breathing.

00:03 So ultimately, the whole job of the lungs is to create gas exchange.

00:09 And so the act of breathing is going to serve to pull in oxygen and essentially exhale or breathe out carbon dioxide.

00:21 And as a system, there's going to be a conducting portion that is really just moving that air in and out and a respiratory portion where the gas exchange is actually taking place at a very small microscopic level.

00:34 So in terms of the conducting portion, we have the trachea.

00:40 And again, at the bifurcation of carina, we have the right and left main bronchus.

00:48 And then after it's reached the lungs, these main or primary bronchi are going to branch into what are called secondary or lobar bronchi.

00:58 And the name will tell you how many you have.

01:00 You'll have three on the right and two on the left, because they'll go to each lobe of the lung.

01:07 From there, they're going to continue to branch into tertiary or segmental bronchi.

01:13 And from there even more and more as subsegmental bronchi, until we reach the level of a bronchiole, which is where there's no more cartilage anymore.

01:24 And it's just really the smooth muscle in the mucosa lining these tiny tiny airways.

01:31 By the time we've reached the very, very tiny areas.

01:35 For example, after we've reached the last part of the conducting portion, which is the terminal bronchiole then we reach the respiratory portion.

01:44 And we're really talking about micro anatomy at this point.

01:46 And very small structures such as alveolar ducts, and ultimately air sacs called alveoli are going to be in very, very close approximation with tiny, tiny branches that are coming from the pulmonary artery which have branched all along the way of these airways this whole time.

02:06 And then after getting oxygenated, these tiny ones are going to form larger and larger veins that will eventually feed into the pulmonary veins.

02:18 So what's happening in a single alveolus, or a single airspace or air sac? Well, through the act of breathing, we've pulled in oxygen from the outside environment.

02:31 And because it's very, very thin, at this point, that epithelium of the alveolar wall is going to allow it to diffuse across it.

02:41 It's going to diffuse across this alveolar wall through a very, very thin layer of protein fibers that connects the alveolar wall to the underlying capillary walls.

02:53 And these capillaries are the tiniest possible branches that are coming from the pulmonary artery.

03:02 And as gas exchange is occurring and oxygen is getting into the blood CO2 or carbon dioxide is being diffused across that same membrane and back into the airspace.

03:15 So the capillaries that have these red blood cells are now fully oxygenated and have taken out there carbon dioxide and they can head back to the pulmonary veins, ultimately to the left side of the heart to be pumped out into circulation.