hi let's talk about the tracheobronchial tree in this video we'll diagram the airway
path in other words the tracheobronchial tree from the trachea to the segmental
bronchi we'll also discuss the cartilages associated with creating an emergency airway
so let's begin with the trachea the trachea is an element distal to the larynx colloquially
the voice box it's suspended from the cricoid cartilage of the larynx by the cricotracheal
ligament it runs anterior to the esophagus which is the passageway between the laryngopharynx
and the stomach and it ends in the primary or main stem bronchi at approximately the level
of the thoracic plane so if we think about the sternal angle with the manubrium above and the
body below and we create that plane back to the intervertebral disc between t4 and t5 it's right
there at that bifurcation right there at that bifurcation inwardly that we have the carina
carina means keel as in the keel of a ship and so here we can see this open up with the right
primary bronchus and the left primary bronchus there and this carine is this ridge between
the two and that ridge is very richly innervated such that if anything is aspirated and comes into
contact with that it would send you into a fit of coughing and bronchospasm so as to hopefully
dislodge that that foreign intruding substance now notice that the uh
the trachea has a number of tracheal cartilages these are hyaline cartilages
that help to maintain the patency of the tracheal passageway posteriorly this is a posterior view
so that's a tracheal cartilage there we can see that that tracheal cartilage is incomplete
that posterior aspect is a combination of connective tissue and smooth muscle
called the trachealis the trachealis which we can see between these two lines helps to determine
the the size of the lumen of the trachea now we refer to this conductive pathway of air as the
tracheobronchial tree it doesn't take a lot of imagination to turn this 180 degrees vertically
to see that this more than enough resembles a tree in passing with the trachea as the trunk
and the remainder of the conductive pathway is the various limbs of the tree so here's our trachea
the trachea divides into two primary bronchi oftentimes called main stem bronchi a right and
a left the right tends to be a little more robust and a little more linear whereas the left tends to
be a little smaller and a little more oblique as we see hearts going to be just anterior to here
so we can imagine it kind of nestled in that area each primary bronchus is going to divide into
several secondary bronchi the right main stem bronchus will divide into
ultimately three secondary bronchi the left into two these secondary bronchi are known as lobar
bronchi because they supply lobes of lungs so on the right here we have the superior
secondary bronchus the middle secondary bronchus and then the inferior secondary bronchus we can
also see that between the primary bronchus and the middle and inferior secondary bronchi
there's this intermediate bronch we call this the bronchus intermedius it's well named and on the
left side we have a superior secondary bronchus and an inferior secondary bronchus those secondary
bronchi are going to multifricate into tertiary bronchi oftentimes called segmental bronchi
segmental bronchi are going to supply an air passage to various bronchopulmonary segments these
are surgically resectable segments that have their own air pathway as well as their very own arteries
from the pulmonary loop coming out to supply them so branches of pulmonary arteries
and these tertiary bronchi are going to give rise to smaller segments called bronchioles
at the level of the bronchial the cartilage in the wall of the conductive pathway is going to
disappear as well as the glands are going to disappear and these bronchioles give rise to
conducting bronchioles conducting bronchioles give rise to terminal bronchioles terminal bronchioles
are called that because they are the termini of the conducting zone so anything beyond the
terminal bronchioles is going to be a site of gas exchange and these are the respiratory bronchioles
so there are three to four respiratory bronchioles per terminal bronchiole and these host alveoli
a vli can emerge directly from the wall of the respiratory bronchial or they may be clustered in
sacks like this and they are what are surrounded by capillary beds supplied by pulmonary arteries
and drained by pulmonary veins keeping in mind that those pulmonary arteries
are going to follow the tracheobronchial tree and the pulmonary veins have no fidelity
to the tracheobronchial tree nor do they have any fidelity to the bronchopulmonary segment
there will be intersegmental tributaries for these veins in terms of aspiration risks
aspiration is whenever a substance other than air is brought into the tracheobronchial tree
most aspirated substances are going to follow the right primary bronchus because
it is larger and more linear with the trachea as opposed to a smaller and more oblique
left primary bronchus so the uh the major pathway not the only but the major pathway will be to the
right and then substances typically continue down through the bronchus intermedius and
depending on their size i mean if they're fluid they can continue through any of the tertiary
bronchi but usually they they end up stuck in that bronchus intermedius
there is one uh bronchopulmonary segment that i would like to draw your attention to and the
tertiary bronchus that supplies it is there on the right side and there on the left side
and that is the superior bronchopulmonary segment of the inferior lobe and these are going to
be clinically significant because the tertiary bronchi that supply these segments are oriented
nearly posteriorly so it's it's a bit of a difficulty to see this in this drawing so
instead of imagining them going down obliquely like that imagine them going directly into the
plane of your screen and so this is significant because if an individual is confined to their bed
for an extended period of time if they're supine they have any sort of infection
fluid may accumulate in that superior segment of the inferior lobe through this conductive
pathway so that's that's one uh bronchopulmonary segment to check for pneumonia and an individual
who's been supine for a prolonged period of time now in terms of airway management in an emergency
uh there is one tried and true location uh and that procedure is called a cricothyrotomy
crico from the cricoid cartilage thyrotomy thyroid cartilage between the two there is that median
cricothyroid ligament that's part of the conus elasticus there are good anatomical landmarks
for this so if you were to palpate your own neck you can palpate your laryngeal prominence and if
you go inferior from that with just the tip of your finger you can feel a little divot before
you can palpate your cricoid cartilage and that divot if you make a noise is going to vibrate or
well what happens if you need to produce an airway because proximal to this
portion of the larynx the the airway is obstructed intransigently um you can incise the skin
and then incise that median cricoid thyroid ligament and cannulate to create an airway
what's nice about this is that there aren't any superficial structures
especially vasculature to get in the way this is for emergent airway it's not for long-term
airway management for that one would perform a tracheostomy or tracheotomy so the uh the
the s is is optional there a tracheostomy is a surgical intervention uh someone would palpate
under surgical conditions the jugular notch and then they would move approximately
one centimeter above that notch they would incise the skin they would part the infrahyoid muscles
so sternohyoid and then sternothyroid muscles then they would skirt the vasculature in this case we
can see the inferior thyroid veins but there's also the possibility of the thyroid ioma artery
ascending there in 10 percent of the individuals and then incise the trachea cannulate and
be able to maintain a long-term airway again tracheostomies are only performed under sterile
or surgical conditions so we've discussed the tracheobronchial tree its pattern of bifurcation
and the the various bronchopulmonary segments that it serves we've also talked about an emergent and
a surgical approach to maintaining an airway this is your summary slide thank you for your time