start off by looking at muscles in this anterior
compartment. Now, there is a warning, there
is a lot of muscles here. There are a lot
of muscles in this anterior compartment of
the forearm. But conveniently, they have been
split up into various layers. And we can look
at these layers individually and the muscles
that lie within each of these three layers,
a superficial, a middle, and then a deep layer.
And we’ll look at these layers individually.
So first of all, we’ll start with the superficial
layer. We can see here on this superficial
layer we have pronator teres, we have flexor
carpi radialis, we have palmaris longus, and
we have flexor carpi ulnaris. These are all
coming from a common origin. So they’re
originating from a very similar place, this
being the medial epicondyle. There can be
some slight variations to where all of these
muscles come from. But the main common origin
is this medial epicondyle here. And we can
see they’re radiating across the elbow joint
and attaching to various places on the forearm
and also in the hand. So we can see pronator
teres is running across to the radius. We can
see flexor carpi radialis is running towards
the second metacarpal. We can see palmaris
longus is running towards the palm of
the hand. And we can see flexor carpi ulnaris
here is running towards one of the carpal
bones. So let’s look at this in more detail.
We can see in the superficial layer, we have
pronator teres, flexor carpi radialis, palmaris
longus, and flexor carpi ulnaris. If we look
at pronator teres, we’ve got two heads of
pronator teres because they have a different
origin; an ulnar head coming from the coronoid
process of the ulna, and a humeral head which
is coming from that medial epicondyle. This
is why it’s important to have those bony
attachments, those bony landmarks from the
osteology lecture previously. The pronator
teres muscle is going to insert onto the middle
of the lateral surface of the radius.
So if we go back, we can see the pronator teres coming
from the medial epicondyle. And also coming
from the ulna, its ulnar head, is passing
towards the shaft of the radius, we can see
it here. We then remind ourselves flexor carpi
radialis, palmaris longus, flexor carpi ulnaris.
And we can look at their attachments. Flexor
carpi radialis and palmaris longus are coming
from the medial epicondyle of the humerus.
So, both of these are coming from the medial
epicondyle of the humerus. As we saw, the
flexor carpi radialis attaches to the base
of the second metacarpal, whereas, palmaris
longus passes towards the palm of the hand
and attaches to what’s known as the palmar
aponeurosis and the flexor retinaculum.
And we’ll look at this as we pass towards the
hand in next lecture. All of these muscles,
pronator teres, flexor carpi radialis, palmaris
longus, are supplied by the median nerve.
The one muscle in the superficial layer that
is supplied by the ulnar nerve is flexor carpi
ulnaris, and this lied most laterally, and
this was positioned most medially within
the forearm. It originates from the olecranon
and the posterior surface of the ulnar, and
it passes to a range of bony landmarks, the
pisiform and the hook of the hamate, also,
the fifth metacarpal. So flexor carpi ulnaris
is passing to these, inserting to these bony
landmarks. It’s different from the other
superficial muscles in this compartment, in
that is innervated via the ulnar nerve. If
we look at the function of these muscles,
well, pronator teres, its name gives it away,
it pronates the forearm. It can also because
it crosses over the elbow joint, flex the
forearm. Flexor carpi radialis is important
at flexing the wrist. It also, because it’s
on this lateral aspect, contraction can abduct
the hand at the wrist joint. Palmaris longus,
this flexes the hand at the wrist. It also
tenses the palmar aponeurosis, the palmar
aponeurosis being a tough fibrous tissue in
the palm of the hand, and tensing this is
important when forming a grip. Flexor carpi
ulnaris is very similar to flexor carpi radialis,
in that it flexes the wrist. But as it’s
running down this medial side, it also adducts
the wrist, or it deviates it to the ulnar side.
So now if we go back and have a look at the
middle layer, then there really is only one
muscle that I really want to talk about in
this middle layer, and that is flexor digitorum
superficialis. Flexor digitorum superficialis,
as its name suggests, is a flexor of the digits.
As we call it, flexor digitorum superficialis,
it means that there’s going to be a flexor
digitorum profundus, and we can see that on this
picture here. But we’re just concentrating
on flexor digitorum superficialis. We can
see that its long tendons pass all the way
to the middle phalanx of the digits. We can see
that here. If we have a look at the attachments
of those muscles, we can see flexor digitorum
superficialis. It has got two heads.
It has got a humero-ulnar head, and this head is
coming from the medial epicondyle.
It’s coming from the coronoid process as well,
and that’s where we have a humero-ulnar head.
It has a part coming from the humerus, the
middle epicondyle, and a part coming from
the ulna, the coronoid process. It also has
a radial head, and it’s coming from the
shaft of the radius. So the flexor digitorum
is coming from a whole wide range of regions
from the humerus, the ulna and the radius.
This muscle belly, eventually, is going to
give rise to long tendons that go and attach
to the middle phalanges of the medial
four digits. So, there are all the digits, but
not including the thumb; so digits 2, 3, 4,
and 5. It’s supplied by the median nerve.
Nerve supply to flexor digitorum superficialis
is the median nerve. Importantly, it flexes
the hand at the wrist joint. It also flexes
the proximal interphalangeal joint. That’s
the joint between the proximal and the middle
phalanges, the proximal interphalangeal joint.
With continued action, it will flex the proximal
phalanges at the metacarpophalangeal joint.
So ultimately, it helps us to form a fist.
It helps us to form a fist. If we then look
at the deep layer, we can see we’ve got