on the radio-ulnar joints. Here, we can look
at the anatomy with all of these muscles put
together. We can see the actual region of
the forearm is quite complicated with all
of these muscles. And here, we’re just looking
at the superficial and the middle layers.
We can see on this superficial layer, we have
those muscles, pronator teres, flexor carpi
radialis, palmaris longus, and flexor carpi
ulnaris. We can see they’re all radiating
away from this medial epicondyle region, and
they’re passing across the forearm.
So we can see pronator teres here, we can see flexor
carpi radialis, and then giving rise to its
long tendon. We can see palmaris longus that is
passing down here towards the palm. And then
we can see flexor carpi ulnaris on this most
medial aspect running down here. So this is
in the superficial layer. We can also see
in this middle layer, we have flexor digitorum
superficialis. Flexor digitorum superficialis
lies deep to this superficial layer.
So to see that, we’ve just cut away a piece of
flexor carpi radialis here. We can see a bit
more of pronator teres running around here. And
we’ve just reflected this muscle, brachioradialis.
So we’ve cut through flexor carpi radialis.
We’ve cut through palmaris longus.
And underneath, we can see this large muscle belly, which
is flexor digitorum superficialis. We can
see here we’ve got its radial head. And
here, we’ve got its humero-ulnar head.
Remember, flexor digitorum superficialis originated
from the radius, the ulna, and the humerus,
and we can see all of those heads. Ultimately,
it was giving rise to a muscle belly. It was
giving rise to four tendons that went to digits
2, 3, 4, and 5. So, as these muscles pass
towards the wrist, they are held in position
by the flexor retinaculum. The flexor retinaculum
is a really important structure, and that
it prevents bowstringing of these tendons.
So it’s held in position by flexor retinaculum,
and also the palmar carpal ligament. And we’ll
see this when we move into the hand. Although
brachioradialis, which is the muscle we can
see being reflected here, this muscle also
flexes the elbow. So although brachioradialis
flexes the elbow, which is similar to what
these muscles do, it is actually within the
posterior compartment. And it’s in the posterior
compartment because it’s supplied by the
radial nerve. So although we can see that
muscles in the anterior compartment flex the
elbow, brachioradialis, although it flexes
the elbow is in the posterior compartment
because of its nerve supply. Brachioradialis
muscle is supplied by the radial nerve, and
therefore, it’s known to be in the extensor
compartment. We’ll come back to it in the
next slide. If we look at the deep layers
of the anterior compartment, then here we
can just see the middle layers once again
with these muscles haven’t been cut and
brachioradialis reflected. What we’ve done
now is we’ve cut through flexor digitorum
superficialis. So here, it’s flexor digitorum
superficialis. And on this side of the screen,
we can see that we’ve cut through it. This
is flexor digitorum superficialis being cut.
And what we can see is flexor digitorum profundus.
Here, deep to flexor digitorum superficialis,
we can see flexor digitorum profundus. We
can see we also have flexor pollicis longus.
So flexor pollicis longus is running in this
direction. We can see it’s coming from the
radius. And also deep in here, we can just
make out pronator quadratus, the deepest of
the muscles. But what we can see here, these
cut tendons, these are the cut tendons of
flexor digitorum superficialis. And deep to
them, we can see now the tendons of flexor
digitorum profundus. Remembering that flexor
digitorum profundus had that dual nerve supply.
The medial muscles, the medial tendons were
innervated via the median nerve, so 2 and
3, and tendons to digits 4 and 5 were innervated
via the ulnar nerve. So here we can see it
quite deep. So now let’s move on to the posterior
compartment. And the posterior compartment is