In this video I want to go back and take a quick look at what is called the bronchial
tree. That is the branching of the airways of the lungs. We've already talked about the
thyroid cartilage, so I'm going to forgo that on this model. I want to talk about the rings
of the trachea, and then the tracheal bifurcation. The trachea is really only about 4 inches
long. From the cricoid cartilage down to its bifurcation at the T4 vertebral level. We
mentioned in the other video that we bifurcate into a left and a right primary bronchus.
The left primary bronchus is more horizontal. The right is more vertical. Primary bronchi
then divide into secondary bronchi. Secondary bronchi. And secondary bronchi then branch
into tertiary bronchi, also known as segmental bronchi. Now on this model each of these color
changes represents a segmental bronchus. However they have in some areas kind of thrown a little
loop on the model, because this is a segmental bronchus, and then they show it branching.
Well it does branch. It's going to branch approximately 20 more times. But not for the
naming in this model. So depending on whether you are in A& P one or A & P two, or human
anatomy, we're going to look at these a little bit differently. In A&P one you are just responsible
for knowing that these are tertiary, or segmental, bronchi. Some books to say that the left lung
will be divided into eight bronchopulmonary segments, and the right lung and a 10 bronchopulmonary
segments. And a bronchopulmonary segment is fed by one of these segmental bronchi. Other
books say that there are 10 in the left and 10 in the right. For our purposes I'm going
to go with ten in the left lung and 10 in the right lung. As I said before, for A&P
purposes you only need to know that these are segmental, or tertiary, bronchi. For human
anatomy we may go a step further. So I want to describe the different bronchi. And the
naming is actually quite simple, although the names are rather long. If we look at,
I'm going to turn this just slightly so we get a better view, I'm going to look at the
left lung first. Remember the left lung has two lobes, a superior lobe and inferior lobe.
And each of those lobs is going to have five bronchopulmonary segments. So in the left
lung we see that this segmental bronchus is heading up for the apex of the lung. We call
that the apical bronchopulmonary segment, or the apical tertiary bronchus, or the apical
segmental bronchus, depending on which terminology want to use. I will use segmental bronchus.
The apical segmental bronchus of the superior lobe of the left lung. Now if I turn this
to an anterior posterior view, this comes toward the front of the lung. This is called
the anterior segmental bronchus of the superior lobe of the left lung. If I rotate this a
little bit, you can see there is one coming out of the posterior aspect headed for the
back of the lung. That is the posterior segmental bronchus of the superior lobe of the left
lung. Then we drop down a ways, and we can see there are two here. One is higher than
the other. This is the superior segmental bronchus of the superior lobe of the left
lung. And this is the inferior segmental bronchus of the superior lobe of the left lung. So
those are the five bronchopulmonary segments or segmental bronchi of the superior lobe
of the left lung. The inferior lobe of the left lung will also have five. The first one
is known as the superior segmental bronchus of the inferior lobe of the left lung. And
on this model we will have to rotate it around posteriorly, because that superior segmental
bronchus actually is exiting toward the back of this bronchial tree. Toward the back of
the bronchial tree. Then on this model we come down further into this inferior lobe
of the left lung and we see here two segmental bronchi. The one closer to midline is called
the medial basal segmental bronchus of the inferior lobe of the left lung. The other
is the anterior basal segmental bronchus of the inferior lobe of the left lung. This one
here actually represents one segmental bronchus. This is called the lateral segmental, excuse
me, the lateral basal segmental bronchus of the inferior lobe of the left lung. And then
this last one here represents the last which is the posterior basal segmental bronchus
of the inferior lobe of the left lung. So five segmental bronchi for the superior lobe,
and five segmental bronchi for the inferior lobe in the left lung. Let's look at the segmental
bronchi for the right lung. Now keep in mind we said there are still going to be 10 bronchopulmonary
segments. So 10 segmental bronchi for the right lung. But we have three loads for the
right lung. So this is going to be a little bit different. On this model this darker orange
color represents the apical segmental bronchus of the superior lobe of the right lung. The
pink color coming toward the anterior is the anterior segmental bronchus of the superior
lobe of the right lung. And if I rotate the model slightly, we can see heading toward
the posterior is the posterior segmental bronchus of the superior lobe of the right lung. So
only three segmental bronchi in the superior lobe on the right lung. Then when we go to
the middle lobe of the right lung. Again we have to look at a posterior view. The superior
segmental bronchus of the middle lobe of the right lung exits posteriorly from this bronchial
tree. Then if we look at the other two remaining we have a medial and a lateral segmental bronchus
of the middle lobe of the right lung. A medial and a lateral segmental bronchus, middle lobe
of the right lung. So there were three segmental bronchi for the middle lobe of the right lung.
Then we drop down to the inferior lobe of the right lung. We can see here this somewhat
green color, the medial basal segment bronchus of the inferior lobe of the right lung. And
over here in this darker blue we can see the anterior basal segmental bronchus of the inferior
lobe of the right lung. Immediately below that is the lateral basal segmental bronchus
of the inferior lobe of the right lung. And at the very lowest, the posterior basal segmental
bronchus of the inferior lobe of the right lung. Now initially these may not look anterior,
medial, posterior, lateral. But remember, if we put this in anatomical position, it
is more upright. And keep in mind the bottom of the lungs are shaped to fit the dome shape
of the diaphragm. So, these lateral can go down further because the diaphragm is shaped
such that the middle aspect of the diaphragm is higher than the lateral aspect of the diaphragm.
And the anterior aspect is higher than the posterior aspect. So the further down we go,
the further lateral and posterior we can go. The very lowest we can get is the very back.
The second lowest we can get is lateral. And then here it is simple to tell anterior from
medial. Although this one looks like it's coming anterior and this looks like it's coming
anterior, it is closer to midline than the others, so this must be the medial, which
leaves this to be the anterior. On the left lung this must be the medial, which leaves
this to be the anterior. So to recap quickly, right lung, three lobes. The superior lobe
has three segmental bronchi. The middle lobe has three segmental bronchi. And the inferior
lobe has four segmental bronchi for a total of 10.