So now let’s move
on to the palmar aspect of
the hand. And the palmar aspect of the hand
contains a whole series of intrinsic muscles
that allow the hand to assume many different
positions. And also, the tendons of the extrinsic
muscles that originate in the forearm pass
through the carpal tunnel to the hand.
Again on the slide, we can see we’ve got the
thumb. We’ve got the second, third, fourth and
fifth digit. So here we have the lateral aspect
and here we have the medial aspect.
We can divide the palmar aspect of the hand into
a number of compartments, and we can identify
numerous muscles within those compartments.
So here again on the slide, we have the picture.
We have this nice central compartment that
contains mostly some deep muscles, but also
the palmar aponeurosis. And the palmar aponeurosis
is continuous here with the antebrachial fascia.
It also connected to a long muscle within
the forearm, palmaris longus, and this helps
to tighten this palmar aponeurosis. The palmar
aponeurosis is important for protection.
It’s also important in being able to form the grip.
It tightens the skin when you’re forming
a grip. So, another space we can see is
known as the hypothenar
eminence. The hypothenar eminence is located
medially within the hand, and we can see there’s
a collection of muscles here, so the hypothenar
eminence. Then we have the thenar eminence
that is associated with the thumb. So we can
see the thenar eminence here. We then have
a small adductor compartment, which is just
here, in between the thenar eminence and the
central compartment. And then deep in between the
metacarpals, we have an interosseous compartment.
And we are now going to explore all of these
Let’s have a look at the palmar fascia, first
of all, and look at the palmar aponeurosis.
And we can see that the palmar aponeurosis is
running over the whole palm but it is actually
thin over the hypothenar and the thenar eminences.
So it’s thin laterally, it’s thin medially.
But it thickens centrally and this is where we
have this triangular-shaped palmar aponeurosis.
The apex of the palmar aponeurosis here is
continuous with the palmaris longus muscle
as I mentioned. And distally, it forms four
longitudinal bands. And these longitudinal
bands pass over the digits and support the
digital sheaths that enclose the flexor tendons
of flexor digitorum superficialis, FDS, and
flexor digitorum profundus, FDP.
Remember, these muscles are originating in
the forearm and they’re passing through
the central compartment deep to palmar aponeurosis
to pass through the digits. And these muscles
are enclosed by the digital sheaths. And these
longitudinal bands help to support those sheaths.
So let’s now look at the thenar eminence.
This collection of muscles is associated with
the thumb. We can see the thenar eminence
is here. What we’ve done is we’ve removed
the palmar aponeurosis on this diagram. So
now we can just concentrate on this space
here, the thenar eminence. The lateral aspect
of the palm, the thenar eminence, contains
three muscles: opponens pollicis, abductor
pollicis brevis, and flexor pollicis brevis.
These muscles are primarily responsible for
opposing the thumb, for opposition of the
thumb, so it can assume a very unique position
where you can draw the thumb across the palm
of your hand, opposition. We can see
these muscles here. Deep within
the thenar eminence, we can see opponens pollicis.
We can see this muscle here, opponens pollicis.
And then we can see that what were being cut
are two muscles. We have flexor pollicis brevis
here, flexor pollicis brevis. We can see the
two cut-ends over here. So we have this muscle,
flexor pollicis brevis, and we have a part
of it here. And then more laterally, we have
abductor pollicis brevis. So we can see abductor
pollicis brevis here and we can see where it has
been cut here. You also have a slightly deeper
head of flexor pollicis brevis, and we can
just make that out deep. It’s at the same
plane as opponens pollicis.
So these are the three muscles that are within
the thenar eminence. We can see the muscles
here in this table highlighting their origins
and insertions. And all three of these muscles
come from the flexor retinaculum and specific
tubercles of the scaphoid and trapezium bones.
So, all of these three muscles have a common
origin. Opponens pollicis inserts onto the
lateral side of the first metacarpal. Abductor
pollicis brevis and flexor pollicis brevis
attach to the lateral side of the proximal
phalanx of the first digit. So just make
sure you’re happy with the origins and insertions
and refer back to the diagram if necessary.
All of these muscles, your thenar eminence,
are supplied by a branch of the median nerve,
and this is known as the recurrent branch
of the median nerve. This nerve runs very
superficial and can easily be damaged. But
these three muscles are supplied by the recurrent
branch of the median nerve. The function of
these muscles really is as their name suggests.
So, opponens pollicis helps to oppose the
thumb. Abductor pollicis brevis abducts the
thumb and it also supports opposition. And
flexor pollicis brevis helps to flex the thumb.
You should make sure you’re happy with the
movements of the thumb.