Alveolar Ducts and Alveoli – Respiratory Zone (Nursing)

00:02 So now that we're done with the conducting zone, let's move into the respiratory zone.

00:08 The respiratory zone begins where the terminal bronchioles now feed into what are referred to as respiratory bronchioles.

00:16 These bronchioles will then lead into our alveolar ducts and finally into the alveolar sacs.

00:25 So the respiratory zone structures include the alveolar sacs, which are going to contain multiple clusters of alveoli.

00:34 And in the lungs, we have millions like hundreds of millions of alveoli.

00:42 The alveoli are the actual site of gas exchange.

00:48 So when it comes to gas exchange we need to exchange gas that is in the alveoli into the blood and conversely gases that are in the blood out into the alveoli.

01:00 This happens across what is known as the respiratory membrane.

01:05 So the blood air barrier that consist of the alveolar and capillary walls as well as the basement membranes of each is very thin and allows for this gas exchange by simple diffusion.

01:19 So all of these structures together these four layers you have the alveolar, cell wall, the basement membrane of the alveoli, the basement membrane of the capillary and then the endothelium of the capillary walls, all four of those structures make up this respiratory membrane.

01:38 The alveolar walls are going to be a single layer of simple squamous epithelia, which are going to be made up of type 1 alveolar cells.

01:48 These are the cells that are going to take part in the respiratory exchange are the gas exchange.

01:55 Also scattered throughout the alveoli wall.

01:58 You have cuboidal type 2 alveolar cells.

02:03 These are going to secrete our alveolar fluid which is going to keep the cells and the air in the alveoli moist as well as surfactant, which is very important for reducing the surface tension of the alveolar fluid.

02:17 And also here we have antimicrobial proteins as well.

02:25 So other significant features of the alveoli include that they are surrounded by fine elastic fibers and the pulmonary capillaries.

02:36 Also, the alveoli are able to be connected to each other or connect it to adjacent alveoli by way of structures known as alveolar pores.

02:47 These pores help to equalize the air pressure throughout the entire lung and also can provide alternate routes for air and the case of blockages.

02:59 Also in the alveoli, we have alveolar macrophages and these are what are there to keep the alveolar surface sterile.

03:08 And throughout the day, you have millions of dead macrophages found in the alveolar area that are eventually swept away by cilia and then swallowed down into our esophagus.

03:22 In this image, I want you to pay close attention to the close intimate relationship between the alveoli and the alveolar sacs and the pulmonary capillaries.

03:36 Also in this trend section of an alveolus you can also see how intimate the alveoli and the blood capillaries are and also how thin the respiratory membrane is.

03:49 Remember this thin respiratory membrane is essential for efficient gas exchange into and out of the blood.