So this is the
ulna bone which we can see in isolation. It
sits within the forearm alongside the radius.
And we can see we have a number of views here
that reveal various bony landmarks.
So let's have a look. The ulna is longer than the radius
and within the forearm it is involved in stabilizing
the forearm and of the two bones it's positioned
medially. So the ulna is medial and the radius
is lateral. Here we can see the anterior
view, here we
can see a posterior view and this view is as
if we're looking at it from the radius.
So as if we are looking at it from the radius is
positioned. We can see it is really a lateral
view as if we were the radius and we have got some
features I would like to detail. So proximally,
up here we have the olecranon we can see that
here on the posterior surface and here on
this lateral view we can see the olecranon
and not proximal kind of extension of the
ulna helps to form this C-shaped cavity and
this C-shaped cavity is known as the trochlear
notch. We can see we've got the trochlear
notch here. We can see we've got the olecranon,
the C-shaped notch which gives rise to this
coronoid process. And just remember, on the anterior
surface of the humerus, we had the coronoid
fossa while this enables the coronoid process
to sit in it when the forearm is fully flexed.
So we can see the coronoid process here when
the forearm is fully flexed. So the forearm is
sitting against the arm, the coronoid process
can sit inside the coronoid fossa and that
add stability to the flexed forearm.
So we have got the olecranon which we can see,
we have got this C-shaped trochlear notch
and we have got this coronoid process. The
trochlear notch is going to articulate with
the humerus, specifically the trochlea of the
humerus. So we have got this kind of barrel
shaped trochlea of the humerus and that is
going to allow articulation with the trochlear
notch. We can also see the coronoid process,
we can see it here on the anterior process we
can see it here posteriorly sticking out somewhat.
Laterally, we can see we have the radial notch,
the radial notch here on this anterior view
and we have got the radial notch here
on this lateral view. And that is important because
that is going to receive the head of the radius.
We also have this crest running down here, known as
the supinator crest and that offers the
attachment of supinator muscle. More inferiorly
from the coronoid process,
we find we have the tuberosity of the ulna
and we will come back to that in a moment.
So some important bony landmarks we
can see on this proximal region of the ulna.
If we look at the shaft of the ulna then that
is not the great deal to really mention just
that it has a sharp interosseous border. So
here we have got the anterior view, we've got this anterior
surface running down here. And we can see
we have got the sharp interosseous border.
We can see it quite prominently here on this
lateral view. The interosseous border is important
because it allows the interosseous membrane
to run between the radius and the ulna.
Distally if we look at the ulna we have the
head, a rounded head and then we have the ulnar styloid
process and this sticks out we can see here
on the posterior surface. We can see it
here and on this anterior view we can see
the ulnar styloid process sticking out.
And this can be palpated medially at the wrist joint.
The distal end of the ulna does not articulate
directly with the carpal bones. There is an
articulation there but it's separated by an
articular disc. And we will come back to that
when we look at the joints.