Hello anatomy colleagues this is Dr Alsup and in this video we will be discussing the
muscle compartments of the hand. And unlike in other compartments thus far
we are not going to really get into the specifics of the individual muscles or identifying those,
as they typically work as units to work on some of the fine control that is found in the hand,
so focusing more on the compartments or the units and the individual muscles as that is how
they are often discussed clinically. Now some of the compartments are named after just one
set of or one muscle so that will come up but for the most part we're just talking the compartments.
I also want to note that these compartments are mostly composed of intrinsic muscles
of the hand, which have both proximal and distal attachments entirely within the hand.
But there are also extrinsic muscles that certainly affect the actions of the joints
in the hand so all those long tendons that we just discussed in the anterior and posterior
compartments of the forearm, those long tendons will certainly be visible in the hand as well.
Additionally our focus will be on the palmer or anterior portion of the hand so this
is an anterior view, and all the views that we'll have from here on out will be anterior views
just different levels in terms of superficial or deep. And the reason that we're focused here is
the majority of intrinsic muscles are located on this anterior or palmar side and this makes sense.
If you feel your palm region your own palm region you can feel squishy or muscle there
then what you feel on the back of your hand which is mostly long tendon and bone so most
of these intrinsic muscles are on the anterior side. Looking superficially in
the palmar region of the hand I think the thing that sticks out to me most is this triangular
white opaque region right here which is the palmar aponeurosis. And this is a thickening of the deep
fascia of the hand, you will have some tendons that will attach there such as the palmaris longus,
and the palm palmar aponeurosis is really there to protect the deeper structures such as the
nerves, arteries, and tendons that are located more in the central compartments of the hand.
It also helps me personally split up the eminences or those moundings of muscles.
There is going to be a larger more lateral thenar eminence and a smaller and more medial hypothenar
eminence. The thenar eminence is associated with the first digit or the thumb so this means that
this is lateral. So these intrinsic muscles that are located right here in this thenar
eminence is they're going to move the joints of the first digit, whereas the hypothenar compartment
is associated with the fifth digit or the more medial digit the little finger
and will move joints associated with the fifth digit. Now note we are looking
at a superficial view of these compartments and there will be deeper muscles associated with each
eminence so we're looking at the superficial most muscles but there are deeper muscles of both the
thenar and the hypothenar eminence. Muscles in both of these compartments will flex abduct and
oppose its associated digits so either the first digit if thenar or the fifth digit if hypothenar. If
you look at your own palm, you can get a pretty set location of where these eminences are
as they present as elevations or mounds under your first digit or under your thumb
and your little finger or fifth digit. Moving to the central compartment of the hand, notice
that the palmer aponeurosis has been removed in this dissection, and this is to be able
to view some of the long tendons from the anterior forearm. So I see a tendon right here,
I see a tendon right here, some of them are a little bit occluded but I see I see them kind
of spread out throughout here there'd be another one here associated it's kind of blocked. And these
are from the flexor digitorum superficialis and profundus muscles, those tendons kind of stack on
top of one another, and we'll distally attach on either the middle or the distal phalange.
Now notice these kind of worm-like muscles which I'm putting an L next to in this region
these are unique. These are lumbrical muscles and these lumbrical muscles have a proximal attachment
on the flexor digitorum profundus tendons so they do not have a proximal attachment on bone.
If you see muscle attached to tendon in the central compartment of the hand, you are you can
definitively say you are looking at a lumbrical muscle, and you can see these really well here
lumbrical lumbrical lumbrical lumbrical right here attached to the flexor digitorum profundus tendons.
You can also see deeper muscles and notice you can see muscles where the thenar and hypothenar
eminences are so these are this is still the thenar eminence and this is still the hypothenar
eminence we're just looking at the deeper muscles in that compartment. You also have an adductor
pollicis so ADductor not ABductor, adductor which even though it does affect the first digit is not
typically included in the thenar compartment. If you get all the way to the bone which we can see
here you see the interossei muscles, so located in between the bones so in between bones interossei.
There are dorsal and palmar interossei muscles these right here are palmar interossei.
I know I'm looking anteriorly here so or on the palmar side because i can see the
pronator quadratus right here which we know is anterior. You can see a peak of the first
dorsal interossei right here kind of in between this lumbrical and the adductor pollicis.
The reason you can see this dorsal interossei from an anterior view is because
the first dorsal interosseus muscle is the largest interosseus muscle so you can see it
from both the posterior and an anterior view. The rest of the dorsal interossei are only visible
from a posterior view which we do not have here on the slide. All right excellent those
are the muscle compartments of the hand in a nutshell. Please take time to review these and
always feel free to reach out to me or any of my anatomy colleagues with any questions