hi let's talk about the bronchial tree the bronchial tree is the conductive pathway that
leads from the larynx down to the alveoli of the lungs so it starts with the trachea and you can
see here's the lyrics there's the thyroid and the cricoid cartilage of the larynx here's the thyroid
gland the lobes of it so here is the trachea and that trick yet descends through the mediastinum
after leaving the neck and it bifurcates into primary bronchi at this bifurcation point there's
a cartilaginous keel called the Carina that is richly innervated so if anything actually makes it
down there and touches that Carina that's going to cause a massive bronchospasm or a coughing
fit to hopefully eject that out so these primary bronchi are going to divide into secondary bronchi
secondary bronchi are going to serve the lobes of the lung and as you can recall there are three
lobes typically on the right side of the lung and there are two lobes on the left side of the
lung and then secondary bronchi are going to spawn into tertiary bronchi tertiary bronchi are going
to serve individual bronchopulmonary segments which are surgically resectable segments of the
lung those tertiary bronchi are going to divide into bronchioles foremost there are terminal
bronchioles these terminal bronchioles are really at the end of the conductive zone so it's it's
here that we have a lot of smooth muscle that can control the the lumen of the conductive pathway
but there's no real means to exchange gases yet those terminal bronchioles are going to host
respiratory bronchioles and it's really there that that we cross over from the the conductive portion
of this bronchial tree to the respiratory zone and so that respiratory bronchial that's going to host
vo lie or the sacks across which there's movement or conduction of oxygen and carbon dioxide and
other gases as as need be so the the bronchial tree gets its name because if you were to take
it and turn it upside down it would look just like a tree and so on the right here we can
see an endo cast of there's a there's the trachea they're the primary bronchi they're the secondary
bronchi as you can see and then the secondary bronchi are spawning many tertiary bronchi there
are approximately nine to ten bronchopulmonary segments on either side so we should have you know
19 or maybe 20 tertiary bronchi as we go and then we can see here on the end a cast those tertiary
bronchi are going down into the bronchioles and that's really at the extent of which the latex
is able to to penetrate the tissue there we're not really going to be able to capture the the
alveoli on this and it's unlikely that we're even going to capture the respiratory bronchioles on
this so here again is the the bronchial tree and we can see it dividing into the primary bronchi
one thing that I would really like you to take notice of is that the right primary bronchus is
a little more linear and it's larger than the the left primary bronchus and so what you have here is
more of a straight shot from the trachea into the the right primary bronchus and we'll discuss why
that's so important with respect to aspiration of materials so as you can see the bronchopulmonary
segments here are color-coded and numbered and they they correspond to the apical the posterior
the anterior segments of of different parts of the the lobes of the lung there's some degree
of variation generally the right side or the right lung has ten bronchopulmonary segments whereas the
left side typically has nine that it may have up to ten bronchopulmonary segments with respect to
aspiration or where materials that do not belong in the bronchial tree go most of the time but not
all of the time they're going to the right primary bronchus and depending on their size they may
either Lodge there or if they're a little smaller they may end up in this spot which is called the
intermediate bronchus it's intermediate because it's intermediate between secondary bronchi but
if it's even smaller than that it may end up in any of these smaller tertiary bronchi now one
thing that is significant is that the superior segments of the inferior lobes you can see them
here as number six tend to be important clinically with respect to the aspiration of materials for
people that are non ambulatory so people that are confined to their beds these tertiary bronchi they
faced posteriorly and so gravity is going to be able to conduct any materials and this is usually
liquids such as exudate into these superior segments of the inferior lobes unfortunately now
here we can see some of these bronchopulmonary segments and i don't think that it's it's very
important that anyone spend much time memorizing them but i do think that it's it's interesting to
sort of see how these vary with respect to the different lobes so there's the superior lobe in
the superior lobe here on the right contains the the apical the posterior and the anterior segments
and then here is the middle lobe containing lateral and medial segments and then here is
that inferior lobe containing superior those that are problematic for people that are confined to
their beds anterior basal lateral basal posterior basal and there's also a medial basal that that
isn't pictured whereas for the left lung there's typically two lobes and so here we can see in a
apicoposterior lobe sometimes there's both an apical and a posterior lobe there's an anterior
a superior and inferior lobe or bronchopulmonary segment to that superior lobe and then the
inferior lobe will have a superior segment a lateral basal and anterior basal a posterior
basil and a medial basal that's not pictured there but you can see down here below so the ultimate
destination on the the pathway that is the the bronchial tree will be these alveoli and so here
we can see the terminal bronchial descending and then branching off into respiratory bronchioles
these respiratory bronchioles are going to be supportive of alveoli or these air sacs and
one thing that I want you to really appreciate is how the secular nature of these alveoli maximize
surface area across which gases can diffuse now when we look at the inside of an individual
alveolus we see that there are two major cells that are important for the wall of the alveoli
the first are type 1 alveolar cells these are simple squamous epithelial cells so they're very
thin and round and flat and these are going to be important for the respiratory epithelium so the
movement of gases in and out of the body the other cell that's going to be important are the type 2
alveolar cells type 2 alveolar cells are cuboidal epithelium and these are going to be important
for secreting surfactant surfactant is important to maintaining surface tension of the alveoli so
that the alveoli stay nice and paitent and don't collapse in on themselves and then the third and
final cell that's going to be important within the alveolus are alveolar macrophages also called dust
cells because they're able to pick up any material that have made it through the conductive path way
and phagocytized them and ingest them so as to to get rid of them so they're not vexing the the
alveolus itself now finally what I'd like to show you with respect to the respiratory epithelium is
that what we have here is that type one alveolar cell so that simple squamous epithelium with a
basement membrane that supports it because basement membranes support epithelial cells
and then we have a simple squamous epithelium of the capillary bed supported by a basement membrane
so we have two simple squamous epithelial cells on either side of a basement membrane sandwich
and that's a very thin passageway it's only about half a micrometer in thickness and so that's very
easy for gases to to diffuse across and owing to the fact that we're able to maximize surface area
with the secular nature of the alveoli that respiratory epithelium can be expanded out
to about 70 square meters that's about 750 square feet that's about the size of a handball court so
that's an amazing amount of respiratory epithelium across which we're able to exchange oxygen and
carbon dioxide so we've talked about the trachea the primary secondary tertiary bronchi the
bronchopulmonary segments the terminal bronchioles the respiratory bronchioles the alveoli and it's
constituencies and how gases are able to move in and out of the body via the alveoli thank you