3D anatomy tutorial on the skeletal features of the thoracic wall, using the BioDigital Human (
This is a tutorial on the thoracic wall. So
the thorax extends from the superior thoracic
aperture to the inferior thoracic aperture.
It's comprised of this bony skeletal framework,
which protects the cavity and the vital structures
within it.
So we'll just take a look at the opening to
the thorax first. So this superior thoracic
aperture is formed at the back by the body
of the 1st thoracic vertebra. And then, the
lateral borders of the thoracic aperture are
formed by the medial margin of this 1st rib,
which I'm outlining here. And then anteriorly,
we've got the manubrium of the sternum and
it forms this nice ring, this aperture or
opening into the thorax.
So structures that enter and exit the thorax
enter and exit through this aperture. So you've
got structures coming from the head and the
neck and you've got structures going to and
fro the upper limbs.
So the inferior thoracic aperture at the bottom
of the thorax is formed by the — we've got
the costal margin anteriorly. And then laterally,
we've got the distal tip of the 11th rib.
And then you've got the 12th rib and posteriorly,
you've got the body of T12. This forms the
outlet for the thorax and it's actually closed
off by the diaphragm.
So you've got the body of the 12th thoracic
vertebra at the back. And then posteriorly
and laterally, we've got the whole of rib
12 and the distal part of rib 11, so the end
of rib 11. And then we've got the costal margin
formed by these costal cartilages anteriorly
and laterally. And then, right anteriorly,
you've got the xiphoid process.
So you can see how the inferior thoracic aperture
is actually closed off by the diaphragm muscle.
So structures that pass from the thoracic
into abdominal cavity pass through the diaphragm
or they pass behind the diaphragm. So you've
got structures like the aorta and the inferior
vena cava as well as the esophagus, which
pass through the diaphragm.
So in terms of the bony framework which makes
up the thorax, you've got the 12th thoracic
vertebra at the back, which make up the posterior
part of the thorax. And then you've got the
ribs which form the lateral part. So you've
got 12 ribs which articulate with the 12th
thoracic vertebra forming the lateral walls
of the thorax. And then anteriorly, these
ribs articulate via a costal cartilage with
the sternum. So you've got these three elements
to the sternum. You've got the manubrium of
the sternum, the body of the sternum and you've
got the little xiphoid process at the end.
So within the thorax itself, you've got three
cavities. You've got two pleural cavities,
which contain the lungs and they sit laterally.
So I'm just drawing this on in red. So you've
got two pleural cavities containing the lungs
in the thorax. And in between these two pleural
cavities, you've got the mediastinum, which
contains the heart and the great vessels as
well as other structures like the trachea
and esophagus, various nerves and other lymphatic
structures.
So the thoracic wall is this musculoskeletal
framework which can protect the vital structures
that lie within it within these three cavities.
Just to mention about the ribcage, you've
got 12 ribs which articulate with the 12 thoracic
vertebrae. You've got seven true ribs and
five false ribs. So the top seven ribs are
called 'true' ribs because you can see this
costal cartilage which sits at the end of
the rib and articulates with the sternum.
So the top seven ribs have this costal cartilage
articulation with the sternum.
And then you've got the five ribs below, ribs
8-12, which are false ribs. So the bottom
two ribs are actually called floating ribs
because they don't have any costal cartilage,
so they're essentially floating, which gives
rise to the name.
And then you've got ribs 8-10, which do have
a costal cartilage because these costal cartilages
actually articulate with the inferior cartilage
of the cartilage above. So they don't have
independent articulations with the sternum.
So these are also called false ribs.
So the top seven are true ribs, the bottom
five are false ribs and the bottom two are
floating ribs.
So that's the skeletal framework of the thoracic
wall.

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