hello all this is Dr. Alsup and in this fourth block of videos we are going to discuss the
musculoskeletal regional anatomy of the thorax, abdomen, and the upper limb
and we're going to start with bones of the thorax so quite a bit to go through obviously our
we've discussed the vertebrae already in terms of the thoracic vertebrae which are a component of
the thorax so that means we need to continue our discussion with the sternum and the ribs which
are the rest of the part oftentimes you'll hear the terms thoracic cage thoracic wall when we're
talking about the thoracic wall generally you're talking about the ribs and the sternum component
and so that's what we'll be focusing more on is that thoracic wall as we've already discussed the
thoracic vertebrae and there's lots of functions associated with the thorax or the thoracic cage
probably the the most intuitive one is that it will protect the organs so obviously we
can think about the organs that we kind of think about more in this area so the heart is going to
be right underneath there the lungs are going to be there but components that are associated
with the abdomen that project a little bit more superiorly such as the spleen a good amount of
the liver a little bit of the kidneys those are also going to be protected by the thoracic wall
also importantly the the thoracic cage is going to play a role in terms
of breathing and helping to facilitate it so that rhythmic type of movement that occurs
with the respiratory muscles will allow for the thoracic cage to expand and that creates
a vacuum which can draw air into the lungs and when that is compressed it will allow air to be
expelled as well so play an important role there as well and then last but not least but obviously
important in terms of musculoskeletal anatomy this region is going to serve as an attachment point
for many muscles that are associated with the upper limb and we'll talk about those when we get
to the muscles so let's talk we'll start with the most anterior bone and this is the sternum
this is going to directly over it's going to be more in the midline it's going to directly
overly much of that mediastinal viscera and there are three parts these are generally
joined by symyphyses even though the literature kind of goes back and forth in terms of some of
that and many times the symphysis will turn into a synostosis or a bony joint in older individuals
the most superior is going to be the manibrium that means handle so it's kind of like the handle
of the sternum I've seen it described as kind of the top of a necktie and I can't kind of get that
out of my head so sometimes that helps there the middle portion of the longest portion is the body
and the most irregularly shaped and most inferior portion is going to be the xiphoid process
when we are looking at the manibrium particularly the superior most portions
of the manibrium there are two two general areas really three when you talk about the pairs
that are very prominent and then in the case of the jugular notch which i'm outlining right here
is palpable so that can help in terms of better understanding that region so right here
in the midline this kind of divot that you can feel right here on yourself
that's going to be the jugular sometimes referred to as the suprasternal notch and the trachea is
going to be just deep to the structure and then on either side of that jugular notch there will
be other divots that during life this is where the medial end or sternal ends of the clavicles
will articulate to create those sternoclavicular
joints which is a type of synovial joint that will allow some movement of the clavicles
now the area between the manibrium and the body is this region right here called the sternal angle
and the sternal angle is also palpable so generally you can palpate the jugular
notch and then move down just a little bit inferiorly and the most anterior projecting
part of the sternum is this sternal angle and so generally what you can do is palpate that sternal
angle and you know that you are at the level of the second rib in terms of where the
second rib will attach and that helps in terms of being able to count ribs
and you'll talk about this a bit more when you get into the the cardio portion of the course but that
can help in terms of being able to to get a better idea of where to put the bell of the stethoscope in
order to be able to to hear different heart sounds so being able to count those ribs is helpful there
moving on to the ribs which have a close relationship to the sternum there are 12
pairs of ribs so there are 12 right ribs there are 12 left ribs there is variation in terms of the
amount but it's not specific to any type of sex or specific ancestries or so forth so there can
be variation but for the most part all individuals are going to have these 12 pairs of ribs
there are what's referred to as true ribs these are generally the first through the seventh ribs
so first is going to be the most superior and they reduce in terms of numbers and they're
called true ribs because each one of these will attach to the sternum via their own
costal cartilage and costal cartilage is just a strip of hyaline cartilage
that's actually a remnant of the the ossification process that occurred so the ribs turned into bone
and then there's this remnant of cartilage that maintains and it helps in terms of the elasticity
of the the rib cage the false ribs also have costal cartilages associated with them but
they have an indirect connection to the sternum so they don't have a one-to-one ratio so you see this
third rib has its own costal cartilage and it goes to the sternum whereas the 8th through the 10th
and sometimes the 7th you will see that these kind of have their costal cartilage but they join up
to form this one connection to the sternum and this will form this costal margin
and then last but not least we have what's referred to as floating ribs or sometimes
you hear them referred to as free ribs these are these do have costal cartilages associated with
them but generally it's just a little bit that does not extend all the way up to the sternum
and so these are generally your 11th and your 12th rib sometimes the 10th rib
between the ribs and the costal cartilages you will have what's referred to as intercostal spaces
and these are named according to the rib forming the superior border so that fourth intercostal
space is going to be between ribs four and five so that's how these are named and this will be filled
in during life with muscles and we'll talk about that when we get to the muscles of the thoracic
of the thorax and then just to to kind of reiterate you do have this fairly prominent
costal margin or arch that is formed by the shared cartilages of those those ribs and this in this
general region these false ribs here and you can palpate kind of where your costal margin is
now we know we talked about how the ribs are going to articulate with the sternum
but they're also going to articulate with thoracic vertebrae and you recall we had
a little bit of this discussion here we've seen this image before so that head of the rib
is going to articulate with the body or bodies of the of these thoracic vertebrae
and then that there is a tubercle you can see this on this rib that's not articulating
just distal to the head that is going to articulate with the transverse processes of those
thoracic vertebrae so you have two separate joints formed by the ribs and the thoracic vertebrae
and I do want to mention one of the more unique ribs the 11th and the 12th ribs are fairly
rudimentary there's not much going on there they're usually pretty distinct in addition
the first rib is quite distinct it is the most curved it's very sharply curved in comparison to
the rest of the ribs it's broader it's shorter and it's a bit more rough because you're going to have
more muscles than just the intercostal muscles that are attaching here specifically and the
anterior scalene is going to attach here which is one of the deep muscles of the neck we didn't
talk too much about this this particular muscle but it is going to to form a fairly prominent
bump or tubercle on this rib now what i think is cool about the first rib is that so it's the most
superior rib as the number one would suggest but a good amount of this rib is actually going to lie
above the level of the clavicle so it is very associated with the root of the neck region
and it's quite deep so it's not easily palpable like many of the other ribs of the thoracic cage
all right excellent we have made it to our review question so the clavicle we'll talk
a bit more about the clavicle when we get to the upper limb but that's going to be your collarbone
I think we're all pretty familiar with where that is that's going to articulate with which part of
the sternum is it the body is it the manubrium or is it the xiphoid process pause the video if you
need to and when you're ready let's talk about how b the manibrium or that most superior portion is
the correct answer so you can see that handle here of the sternum articulating with the clavicles on
on either side and those clavicular notches that we discussed so it makes sense the clavicles are a
bit more superior so it's going to be articulating with that superior most portion and I really think
that this is a cool joint this is where you're having the articulation of bones of the upper
limb with the axial skeleton it's really the only place that that occurs so we'll talk a
bit more about that when we get to the upper limb as well all right thank you so much for your time
and attention here as always please reach out if you have any questions see you in the next video