All right. Now, let's continue our discussion
of the upper limb by going to the elbow
and we're going to start with
where we left off last time with the humerus.
At the distal end of the humerus, we see that there are these bumps
on either side called the lateral epicondyle
and the medial epicondyle on the lateral,
medial sides, respectively.
Epi means upon and there are
these sideways projections of a condyle
which is the round part that's actually going to articulate
with the bones of the forearm
but those portions are covered by articular cartilage
because all ends of bones ideally at joints
are going to be covered in cartilage
so bone isn't rubbing up against other bone.
Distally in the elbow joint,
we have two forearm bones.
On the lateral side, we have the radius
and on the medial side we have the ulna.
And it's always good to remember when we talk about medial
and lateral or really any anatomic terms,
we imagine we're in the anatomic position
with the upper limbs resting at our sides
and our palms pointing forward so that way we have an idea
in our mind which side is lateral, which side is medial.
Here, we see an x-ray of the elbow and we can make out the humerus
because of how wide it gets out those epicondyles
and then we can see the forearm bones with,
again, the radius being lateral and the ulna being medial
and one thing you'll notice is it looks very dense
or very bright white at the very superior end of the ulna
where it almost looks like it's overlapping with the humerus
and that's what's actually happening.
We have to actually go to a lateral view
though to see why it's overlapping.
And from a lateral point of view,
we can see how the elbow is really a hinge joint
because we have the humerus
coming down meeting the radial head
and then the ulna really cups it and it sort of provides this socket,
if you will, for the rest of the humerus to fit nicely into
and it's around this axis that will have our hinge-like movements.
So here, we have an x-ray where we see it in a lateral position.
So, again, with the humerus
coming down to the radius and ulna
and we can see the ulna forms this cup-like structure
so it can receive the humerus
and that tells us a little bit about the movement
that's going to happen at the elbow joint.
It's not going to have a whole lot of movement because it's constrained
by this cup-like configuration and can really only move in two directions.
We can have a little bit of extension
from a neutral position and then a lot of flexion,
and of course the opposite of that
will be going back to extension again.
So we really have flexion and extension and it acts,
basically, as a hinge so it's a prototypical hinge joint.
If we look at the forearm a little bit more,
it's quite a bit different from the arm because we have two bones here
and there's going to be a lot of things
that need to connect these two bones so they act in unison.
So, again, we have the ulna and we have the radius
and going all the way in between is this connective tissue sheet
called the interosseous ligament.
Interosseous just meaning between bones.
If we zoom in at the proximal end
where it's near the elbow, there's a lot more.
We have a radial head that's going to be part
of the articulation at the elbow joint
and a neck separating that head from a bump or tuberosity
on the radius called the radial tuberosity.
And when we have these bumps on the bone
is because they serve as attachment points for muscles.
Similarly, that cup-like shape of the ulna
has a posterior portion called the olecranon
and then it's giving rise to a little notch
called the trochlear notch.
Trochlea means pulley and then a coronoid process on the other side
so that the distal end of the humerus
is actually nicely wedged in between
the olecranon and coronoid process.
And the ulna has its own bumps or tuberosities for muscles to attach to
and they're called the ulnar tuberosity.
Between the two bones,
we do have a proximal radioulnar joint.
And where there's a proximal joint,
we can generally assume there's going to be a distal joint.
We do have a distal radioulnar joint as well.
At the distal end of these bones,
you can see they're almost the opposite.
Proximally, the radial head was really small
and the ulnar was really wide.
Distally, the radius become fairly wide and the ulna has a smaller head.
It's almost like they're flipped.
And at the edges of both of these bones,
we have little projections called styloid processes
and they look like they're kind of reaching out
and almost forming a cup-like shape here as well
and that cup like shape is where we're going to
find the first bones of our hand.
And when we're talking about the wrist and hand,
the first thing we talk about proximally are those carpal bones
that are wedged right up against the distal end of the radius and ulna
and beyond those carpals are the metacarpals.
That's actually what meta means, next, so beyond the carpals,
the next thing after the carpals are the metacarpals,
the bones that make up the majority of your palm of your hand.
And then, distally on the digits, we have the phalanges
and the fingers or digits two, three, four, five have a proximal, middle,
and distal but the thumb only has a proximal and a distal.
The movements at the wrist are similar to those of the elbow
and that we have extension and we have flexion.
We also have movement in a little more degrees
of movement than we do in the elbow
and that's because if we think back to our anatomic position,
with our palms pointing forward,
this would be a posterior view of the right hand and we think,
okay, the thumb in this sense is actually lateral to the pinky.
That way when we make a motion
where our pinky is moving towards the midline,
that would actually be adduction similar to the adduction of the arm
that we saw at the shoulder joint, just on a smaller scale.
And if we move our thumb outward
again, we actually will get abduction
so it's a smaller scale movement
but same ideas what we had at the shoulder joint.