Welcome to this lecture on “The Thoracic
This slide depicts the learning objectives
that you should be able to answer at the conclusion
of this lecture.
First, describe the osteology of the thoracic
wall that is ribs, sternum and thoracic vertebrae
and the intercostal spaces.
Compare and contrast the movements of the
thoracic wall and cavity.
Describe the thoracic apertures.
Categorize thoracic muscles as extrinsic and
Describe the attachments, innervation and
actions of the thoracic muscles.
Describe the neurovascular structures of the
And then we'll summarize the key take-home
messages from this lecture.
And then we'll provide attribution for the
images that were used throughout this presentation.
This is our body map and the thoracic wall
will have an anterior aspect to it, a lateral
aspect and then we also have posterior structures
that are associated with the thoracic wall.
So, that will be our focus for the remainder
of this presentation.
And that we'll begin with the relevant osteology.
And so, our focus here will be on the ribs,
sternum and thoracic vertebrae. But first,
we need to understand the fact that we have
12 pairs of ribs. And we can count those 1,
2, 3, 4, 5, 6, 7, 8, 9, 10 and then, more
posteriorly, we can see 11 and 12. If we stick
with the posterior view, you can see that
there are spaces between the ribs and these
are termed intercostal spaces. We will have
a total of 11 intercostal spaces.
Ribs can be classified on the basis of their
attachments and whether or not they are true
ribs or false ribs. We can categorize ribs
as being vertebrosternal, vertebrochondral
or simply vertebral. Vertebrosternal ribs
are the first seven pairs 1, 2, 3, 4, 5,
6 and then here is 7. At the anterior aspects
of the first seven pairs of ribs, you will
see these blue bars of hyaline cartilage.
They are termed costal cartilage for each
rib and they will connect each of the first
seven vertebrosternal ribs directly to the
sternum. Because of this direct connection
between the costal cartilage to the sternum,
these are called true ribs.
The vertebrochondral ribs would be ribs 8,
9 and 10. And if we take a look here, here
is number 8, here is number 9 and then here
is number 10. You will see that they too have,
on their anterior ends, costal cartilages,
but they will then, instead of attaching directly
to the sternum, these costal cartilages will
connect to the costal cartilage above. So,
here's the costal cartilage of rib number
8 and you can see it connects with the costal
cartilage of rib number 7.
Similarly, rib number 9 intersects or connects
with this portion of the costal cartilage,
and then the 10th one does so as well. The
name for these false ribs would be vertebrochondral
because of their posterior attachment to the
vertebral column and their anterior attachment
to the costal cartilages.
The last two of ribs just have vertebral attachments
to the thoracic vertebrae, the lower two,
and no anterior attachment. So here, we see
number 12, here we see rib number 11. They
just have posterior vertebral attachments
and they do not have a direct anterior attachment
to either of the costal cartilages and they
certainly do not connect to the sternum.
We can also take a look at ribs to best understand
some of their osteologic features. And we
can classify ribs in this context as either
being typical ribs or atypical ribs. We first
want to understand the basic architecture
of a typical rib and typical ribs will be
rib pairs 3 through 9.
The osteologic features of a typical rib,
and we’re going to focus on these two illustrations
here in the image. The typical features would
include a head and there are two articular
facets to the head of the typical rib. Just
distal to the head of the rib, the rib will
narrow and for a very short distance, you
will have what is known as the neck of the
rib, also shown in the illustration above.
And then just distal to the neck of the rib,
there will be an expansion of the rib and
this expansion is known as a tubercle.
And you can see this blue-colored area in
this portion of the illustration as well as
the rib above and that will serve as an articular
process for a transverse process of the thoracic
vertebra. Just distal to the tubercle, you
can see that the rib makes a band and it will
be directed inferiorly and anteriorly at this
band. This band represents what is known as
the angle of the rib. And just anterior to
that angle, this is typically the most common
point for a rib fracture because this is the
weakest point of a rib. And then if you look
on the inferior aspect of a rib, you will
note the presence of a costal groove.
Atypical ribs would be rib pairs 1, 2 as well
as 10, 11 and 12. The features of atypical
ribs are going to deviate from those that
we just went over with respect to a typical
rib. And of these atypical ribs, the most
unique and peculiar rib is actually going
to be rib 1. And we see rib 1 in the upper
portion of this illustration and its head
will articulate with just one thoracic vertebra.
That’ll be T1. It is highly curved and tends
to be more shelflike rather than directed
upwards and downwards and the top of the shelf
presents two grooves. This groove is more
anterior to this one and the subclavian vein
crosses over rib 1 in this anterior groove.
And then lying behind the subclavian vein
is the subclavian artery and it will course
through the groove located here.
If you're very interested in some of the other
features that deviate from a typical rib,
I would direct you to your anatomy textbook.
We probably don't need to overly focus on
some of those features that do deviate from
the typical ribs.
The sternum is another osteologic feature
of the thoracic wall. It will lie in the anterior
midline. The sternum has three parts to it.
We have a manubrium and then the superior
portion that we see here notched within the
manubrium is the jugular notch. And then we
have clavicular articulations here. So, the
clavicle on each side articulates at this
particular point. The manubrium makes an articulation
or joint with the main portion of the sternum
and this is termed the body. And then the
most inferior component of our sternum is
the xiphoid process. And in the illustration,
the xiphoid process in this example is bifid
and it can come in different morphologies
or forms. I do want to point out this area
right in through here where the manubrium
does articulate with the body of the sternum.
And if we shift our attention here to this
lateral view, you see the manubrium. You see
the point of articulation with the body and
you can see that there is a slight angle as
a result of this articulation. This is the
anterior portion. It is readily palpable on
the anterior thoracic wall and this angle
represents the sternal angle or the angle
At this angle, you see a point of connection
for the costal cartilage of rib 2. And so,
by identifying the sternal angle and going
laterally from there, identifying it here
in the anterior view and go lateral in either
direction, you can then identify the level
of rib 2 and then you can count your ribs
below that if you have to identify some of
the intercostal spaces.
Since all the ribs have an attachment to thoracic
vertebrae, let’s pause for a moment and
look at how the ribs do articulate with the
thoracic vertebrae. Many of your ribs are
going to articulate with two successive thoracic
vertebrae. So, if we take a look at the example
here, we have a rib and for the purposes of
explanation, let’s say this happens to be
rib number 6.
One of the facets on the head, the more inferior
one, will articulate with the 6th thoracic
vertebra as is shown in the illustration.
Here is the superior facet on the head of
the rib. It’s going to articulate with the
inferior aspect of the 5th thoracic vertebra.
And then if we look at the tubercle, here
we can see the tubercle of rib 6 articulating
with the transverse process of the 6th thoracic
There are some exceptions with respect to
how ribs articulate. Ribs 1, 10, 11 and 12
just will articulate with their respective
vertebral level. So, rib 1 just with T1, rib
10 with just T10, rib 11 with just T11, rib
12 just articulates with T12. And then the
transverse processes associated with thoracic
vertebrae 11 and 12, there is no articulation
of those transverse processes with the tubercles
of the ribs at that level.