Hey, What’s up. Meditay here. Let’s talk
about the anatomy of the respiratory system. In this segment, we will be talking about
the anatomy of the Trachea and the Bronchi. Alright, so the respiratory system consists
of all the organs involved in breathing. These are the Nose and the nasal cavity,
Pharynx, Larynx, Trachea, Bronchi and the Lungs. In our last two videos, we covered the
anatomy of the nasal cavity and the Larynx. Now let’s do the anatomy
of the Trachea and Bronchi. So In this video, we're going to cover the
anatomy of the Trachea, which includes the parts that make up the trachea, and the layers
of the tracheal wall. Then we're gonna cover the bronchial tree and the Alveolar tree and then
we’re going to compare the Layers of the Tracheal, Bronchial, and Bronchiolar wall to really
understand the anatomical differences of structures as you get closer to the lungs.
Alright, so here we see the anterior view of the chest. The Larynx is up here, and inferior
to it, you’ll see the trachea. Now, let's remove the bones to see them better. As the trachea
descends, it divides into two mini tracheas that enter each lung. If we now remove the lungs,
you’ll be able to see those mini tracheas, we call them bronchi. So now, let's remove the
bronchi to focus on the anatomy of the trachea. Now another name for the Trachae is a windpipe
as it's a tube responsible for directing the air into and from the lungs.
And the trachea can be between 9 to 15cm long. and roughly about 2 to
2 and 0.5 cm in diameter. And the trachea goes from the six-seven cervical vertebrae down
to the fourth, fifth thoracic vertebrae. Let’s now focus on the specific parts that make up
the Trachea. The first thing you notice are those horseshoe shaped cartilages shown here in green,
and their horseshoe-shaped because they don't really cover the backside as you see right here.
And you have many horseshoe-shaped cartilages stacked up on top of each other for a
smooth airflow. These cartilages are called Tracheal Cartilages, and they very
much resemble a horseshoe as you see here. And between each of these tracheal Cartilagines,
you're gonna have ligaments connecting them as you see right here in green. And those ligaments
are called Annular Ligaments, containing strong fibers that connect each adjacent
cartilage together. And then on the backside, as you see right here in green, you're gonna have
a fibromuscular membrane connecting the tracheal cartilages together at their dorsal edges, we call
it the membranous part of the Trachea. So again it consist of Tracheal muscles and connective tissue.
So that's basically the structures of the trachea. Now let’s look at the layers of tracheal
wall, by making a transverse cut. Remember we’re still going to have the membranous
part back here and the tracheal cartilages. Now I want to focus a little bit on
the tracheal walls with the inner walls highlighted right here in blue. So the
innermost structure you'll find is this one, the tunica mucosa. And the tunica mucosa contains
Tracheal Lymphoid Nodules which help fight against microorganisms in the air, and it also contains
tracheal glands that lubricates the surface of the respiratory tract that make it more adhesive
to any irritants or organisms in the air, and once these irritants are cought, you’d
usually start coughing to aid in removing these. So that’s the tunica mucosa.
The next layer we have is the tela submucosa, which contains loose connective tissue and blood
vessels. Then you know we have the cartilages and the membranous part of the trachea, but externally
to that, we have the outermost layer called tunica adventitia consists of dense connective tissue
for protection. So it do have the general layout of any tube in our body. Now the trachea starts
off at the Larynx and then goes all the way down until it splits, and the area where it splits is
called the tracheal bifurcation, as you see here. And at the region where they split, you’ll
find a small elevation on the inside. So if we make a transverse cut a look at it from this
perspective, you will see this right. There’s an elevation here at the bifurcation we call Carina
of Trachea, which is essentially just a ridge of the last cartilage protruding into the lumen of
the trachea, right before it becomes the Bronchi. And just don’t forget that the esophagus is
still located right behind the trachea here. Now, let’s do the anatomy of the bronchi.
So, as a trachea splits into two bronchi. We get the right primary bronchus, or the right
main bronchus, and the left primary bronchus. And they split at the region of the fourth,
fifth thoracic vertebrae as you see here, where the trachea ends. Alright. The right
primary bronchus and the left primary bronchus differ in that, the right one is about 2.5 cm
long before it enters the lungs. So It’s shorter, wider, more vertical than the left one. The left
one is about 5 cm long before it enters the lungs. It’s longer and more narrow. And this is before
they both enter the lungs really important you get that principle. And here is something I
need you to never forget, that the left main bronchus curves more than the right main bronchus
as you see here aswell. And why is this important? Well, in clinical perspective, there’s a
condiction called foreign body aspiration, where a person inhales a foreign object into
their airways, this ostly happen in children. But imagine, when a person inhales any type of object,
small enough to enter the respiratory tract. If it gets far enough, which side do
you think the object will fall into? Most commonly into the right one, since it
doesn’t deviate much from the tracheal axis as you see here. If the object haven’t
gone far down the respiratory tract, you could try the Heimlich manneuver. If it’s
far down into the lower respiratory tract, you gotta get in there with a bronchoscopy
and either suck or pluck it out. Now I reckon you’ll never forget this. So The
right and left primary bonchi will enter the lung through the Hilum of the lung,
which is the entrance into the lung, and from here it’s going to divide into smaller
bronchi according to the lobes of each lung. There are three lobes on the right lung, so the
right one will divide into 3 Lobar Bronchi, or bronchi lobares dexter. The left lung has only two
lobes, and this give us two left lobar bronchi. So after that, after they’ve divided into each
lobe, they’ll further divide into segmental bronchi. The right one will divide into 10
segments and the left one into 8 segments, according to how the lungs are built. Alright. So
again the primary bronchus becomes lobar bronchi, which then becomes segmental bronchi
Let’s now do that one more time, but this time a little more detailed
cuz it’s important to know this. Primary bronchus goes through the hilum of the
lungs. As you see the right lung has 3 lobes, the left one has 2 lobes. So the right one
will brach off as the Superior Lobar Bronchus, Middle Lobar Bronchus and the Inferior Lobar
Bronchus. The left one will branch off as the superior and inferior lobar bronchus. Now let’s
do the full bronchial tree on the right side. Here is the right lung. It has a Superior Lobe,
Middle Lobe and Infeiror Lobe. And if we look from this direction, youll be able to see the hilum
of the lung, the place where the bronchi enters the lung, and branch off to each of these lobes as
the superior, middle and inferior lobar bronchi. Each of the Lobes are anatomically divided into
Segments. The right lobe is divdided into 10 segments and the left is divided into 8 segments
in total. And this is where the lobar bronchi will divide into segmental bronchi, according to the
segments of the lobe. And this is also surgically important because if there are any tumors or
any other indications to surgically resect a part of the lung, we can do that according to
the segments. In this way we won’t damage other parts of the lungs by damaging these bronchi.
So I made a quick scheme which you can use if you want to, but the bronchial tree consist of the
right and left main bronchi, which divide into 2 or 3 lobar bronchi. 3 on the right lung and 2 on
the left lung. They will divide into segmental bronchi. 10 for the right lung and 8 for the left
lung. And they will keep splitting 6-12 times until they become reeealy small, approximately
0.5-1 mm in diamenter, now called bornchioles, or Terminal Bronchioles. Which will be the end of
the bronchial tree. Now what is specific with the bronchial tree? The inner lining of the bronchial
tree consist of respiratory epithelium, which are specifalized epithelium with cilia, those hail
like structures on the surface are cilia. The only function the bronchial tree has is air conduction
and protection, by catching whatever irritants may be in the airway, and pull them upwards so you
can cough them up. But as you get deeper into the lungs, these lining epithelia starts flattening
out, so at the end of the bronchial tree, approximately at the terminal bronchioles, these
respiratory epithelium will change into cuboidal like epithelium, and this is where we say that
the bronchial tree continue as the alveolar tree. So again we have terminal bronchioles,
which will continue as primary bronchioles And already here, you can see these bumps on
surace of the alveolar tree, called alveoli. The alveoli are our primary area for gas exchange, so
that we can receive oxygen. You’ll notice that the deeper into he lungs we get, the more alveoli
we’re going to have. So secondary bronchioles are gonna have even more alveoli, and tertiary
bronchioles are gonna have even more alveoli. These names really depend on which sources you’re
studying from. They’re also called Respiratory bronchioles in some sources. After the tertiary
bronchiole, we’re going to have the alveolar ducts, which is going to lead into our alveolar
sacs, which are sacs with a lot fo alveoli for gas exchange. They’re highøy vascularized as you
see here. Now again, the bronchial tree will have respiratory epithelium, the deeper ito the lungs
you get, the flatter the epithelium will become, and in the alveolar tree, we’re mostly going to
have these simple squamous epithelium, which are thin epithelium that help with the gas exchange.
Now lastly, let’s compare the layers of the tracheal, bronchial and bronchiolar wall. And
we'll start by going through the trachea again. So the inner layer is tunica mucosa, remember,
lined by respiratory epithelium. And then you're gonna have the Tela submucosa with a lot of loose
connective tissue. Then the horseshoe-shaped Tracheal Cartilage with the smooth muscles on the
backside called the membranous part of trachea. And then they're all protected by
the layer of tunica adventitia. So as we look at the bronchus, we
also have tunica mucosa on the inside, lined by respiratory epithelium, since
it’s a part of the conductive airways. Underneath, we have the loose CT, called
Tela submucosa. Then externally to that, the muscle layer, the cartilage, and the fibrous
layer are gonna blend into eachother, into a layer called FibroMusculoCartilaginous Layer, simply add
fibers, muscle and cartilage together. Notice here that the horseshoe-shaped cartilage is gradually
starting to disappear as it become fibers. So externally to that again, tunica adventitia,
the dense connective tissue for protection. As we look at the bronchiole. The inner layer
is still gonna be tunica mucosa, lined by either cuboidal or simple squamous epithelium. and then
Tela submucosa. And then, the cartilage and the fibers are completely replaced by smooth muscles
called tunica muscularis. And then you're gonna have a layer of Tunica adventitia on the outside.
So that was all I had for the anatomy of the Trachea and the Bronchi of the respiratory system.
Our next video is going to be about the Lungs.