Hello all this is Dr Alsup and in this video we will be discussing the basics of the bones
or the osteology of the upper limb. Much to do here so let's get started!
We will start with our old friend the clavicle or colloquially referred to
as the collarbone. This bone is kind of a strut between the thorax, this region,
and the upper limb region and is palpable for most individuals throughout its length.
There is a sternal or medial end which I typically describe as being more bulbous it looks a little
bit more circular and as its name would suggest it's going to articulate with the sternum.
And it also has an acromial or lateral end which appears more flattened in comparison
to the medial end and this is going to articulate with the acromion of the scapula.
We will be spending quite a bit of time on the scapula in upcoming sessions but for now
just a reminder of location of this bone. This bone is often referred to as the shoulder blade
and can be seen from an anterior view in terms of these projections right here and the glenoid fossa.
But it's really most prominent when you're looking at a posterior view where you can really see the
body and size of the scapula. So certainly more to come in upcoming sessions regarding the scapula.
The humerus articulates with the scapula at the head of the humerus which is the ball
in the ball and socket joint that is the shoulder joint here's the socket right here of the scapula.
The head always points medially when you're trying to get oriented so it's heading
towards or in the direction of the thorax.
Looking at the distal end of the humerus it widens again
and that makes sense as it will be forming joints again
and in this case we're talking about the elbow region when we're talking about the distal humerus.
Any time that you have a smooth area on bone this is a good indication that that portion of bone
plays a role in joint formation, there would be articular cartilage there during life.
The trochlea which I'm outlining right here, is kind of spool shaped is more medially placed
and will articulate with the ulna to form the humeroulnar joint which is the true elbow joint.
I think the trochlea is pretty distinguishable from the more bulbous capitulum over here which
is just lateral to it but if I'm still confused and i'm trying to get my bearings I look to see
which one is next to the more distinct projection just superior to it, which right here this is
the medial epicondyle we'll talk more about that in terms of it's being attachment site for forearm
muscles. But the the articular surface that's closest to the medial epicondyle will be the
trochlea. Now if you flip the humerus to see a posterior view so this is an anterior view
this is a posterior view and I know that because you see this prominent depression right here
called the olecranon fossa. And this is where the olecranon of the ulna or the point of
the elbow so if you're feeling the back of your elbow region that bone right there, if it's
in the olecranon fossa during full extension of the elbow joint so you
do need a depression on the humerus in order to be able to receive that portion of the bone.
Moving to the bones of the forearm of which there are two. The ulna is the medial forearm bone
and it's significantly larger or more complex proximally, so this is proximal or superior, and
tapers to much smaller as you move distally. And this has everything to do with the fact that the
ulna plays a dominant role in the elbow joint and little and no articulating role in the wrist joint.
There are two dominant structures on the proximal portion of this bone.
On the posterior surface of the ulna so this is a straight anterior view here so you can't see it
very well but you can see over here this posterior surface right here is the olecranon. And again
this is a robust region it's the point of the elbow so easily palpated on the posterior portion
of the elbow it's built up because that triceps brachii muscle is going to attach there.
More anteriorly placed there is this semilunar notch
right here and you can see it right here as well. This is called the trochlear notch and
this is going to articulate with the trochlea of the humerus that we saw in the previous slide.
The radius is the more lateral forearm bone and it has kind of an opposite pattern from the ulna
it's going to be smaller proximally as it plays a smaller role in the elbow region
and widens as you move distally because it plays an important role in the radiocarpal
or wrist joint. And let's discuss structures on the ends of these bones. The head is this button
shaped circular region at the very proximal most portion of the radius, and this is going
to articulate with both the capitulum of the humerus that we saw on the distal end of the
humerus as well as the radial notch of the ulna so it's going to form two separate joints there.
On this distal most end in fact you have to kind of flip the bone over to really
see, you see this area right here called the carpal articular surface.
This is really nice and smooth indicating that there was hyaline cartilage there during
life and plays a big role in terms of joint formation specifically in terms of the wrist joint.
Now we have finally reached the wrist and hand so we will start proximally and move distally.
Shaded in green here you have the carpal bones which are often referred to as wrist bones of
which there are eight and you're going to have two separate rows you'll have your proximal row
and your distal row of carpal bones. Shaded in orange are the metacarpals and these are
located in the palm region and are numbered 1-5 from lateral to medial so this stout bone
right here is the lateral most and it is the one associated with the thumbs and so the
bones associated with the thumb are going to be numbered 1 and they're the lateral most.
So the first digit in the hand is lateral which is the opposite of what occurs in the foot with
the first digit being medial. I always remember first digit in hand is associated with the thumb
first digit in the foot is associated with the big or great toe and then I can kind of count from
there. So this would be the first metacarpal second third fourth and the fifth will be the medial most
in terms of the metacarpals. There are three types of phalanges named based on relative location.
Shaded in pink are the proximal phalanges which are numbered in the same scheme as the metacarpals,
in light purple you will have the middle or intermediate phalanges notice that there is
not an intermediate phalange or middle phalange in the first digit that's why there are 14 phalanges
not 15, and lastly in light blue you will have the distal phalanges which are quite distinctive
in shape this interesting shape like that.
Excellent that was the basic introduction to the bones of the upper limb. Please take time to look
at this image that gives a complete picture of the bone so you can see the relationship with other
bones and you can appreciate things a bit more. Notice how much longer the humerus is than the
other bones, notice that the ulna is medial and the radius is lateral, things like that kind of
just use this to to kind of take in everything that you just learned in the previous slides.
I thank you for your time and attention here and always feel free to reach out
to me or any of my anatomy colleagues with questions. Have a great rest of your day