Bronchi and Subdivisions – Conducting Zone (Nursing)

00:02 So after the trachea we're going to branch into what's known as the bronchi.

00:07 The air passages are going to undergo twenty three orders of branching.

00:13 This branching is referred to as the bronchial tree because when you turn it right side up, it kind of looks like a tree.

00:22 From the top of the bronchial tree, we start with a conducting zone and then it gives rise to a respiratory zone.

00:31 In the conducting zone, we're going to be conducting air into the lower respiratory tract and in the respiratory zone, this is where gas exchange is going to take place.

00:43 So in the conducting Zone the trachea divides to form the right and the left main or primary bronchi.

00:53 Interestingly the right main bronchus is wider, shorter, and more vertical than the left.

01:00 And so if a person is to inhale an object, it's more likely to go into the right main bronchus.

01:09 Each main bronchus enters into the hilum of one of the lungs either the right or the left lung.

01:16 At this point they are now going to branch into the secondary bronchi also known as the lobar bronchi.

01:24 The reason they get this name lobar is because each one is going to correspond to one of the lobes of the lung.

01:32 So there are three on the right and two on the left.

01:36 Again, each lobar bronchus supplies one of the lobes on the lungs.

01:45 And the end of the conducting zone we are now going to go into the tertiary bronchi also known as the segmental bronchi.

01:54 We call them segmental because they start to divide into multiple segments.

01:59 Each branch becomes smaller and smaller until we get to the point where once we're less than a millimeter in diameter.

02:07 We are now referring to them as bronchioles.

02:11 At the very end of the conducting zone, are terminal bronchioles get as small as less than a half of a millimeter in diameter.

02:23 In the conducting zone where we go from bronchi to bronchioles several different changes occur.

02:30 First, the support structures of this area are going to change.

02:35 The cartilaginous rings that we started with in the trachea, are now going to become irregular plates and as we get to the bronchioles, we're going to replace the cartilage with elastic fibers.

02:50 The epithelium is also going to start to change.

02:53 Recall that we start with a ciliated pseudostratified columnar.

02:59 This is going to eventually give way to cuboidal cells.

03:04 Also the cilia and the goblet cells are going to become more sparse.

03:10 So if we start with the primary bronchi, basically what we have is that the beginning we're starting with ciliated pseudostratified columnar cells, and then as we get to the larger bronchioles, this is going to change into ciliated simple columnar cells that still contain goblet cells.

03:30 And then from there we're going to as we get to the smaller bronchioles.

03:35 We get ciliated cuboidal cells that do not have goblet cells at all.

03:40 And as we get to the terminal bronchial we have non ciliated cuboidal cells.

03:48 Another change that occurs is going to be the amount of smooth muscle.

03:53 So as the cartilage disappears, we're going to get more smooth muscles and this is going to become important because this is going to help us to provide substantial resistance to air passage in the bronchioles.