00:00
So now let's move on to the short muscles and how that arranged alongside the
extrinsic tendons. So here we can see some deep dissections of the hand. We can
see that we've cut away some of the tendons and we've opened up the carpal tunnel
and here we have removed some of those tendons as well to look deep and see some
dorsal and palmar interossei muscles. So if we have a look, we can see the all 8 tendons,
see them here, flexor digitorum profundus. And we can see the cut tendons here,
flexor digitorum superficialis, and to the central compartment of the hand by passing
through the carpal tunnel. And if you remember, FDS, flexor digotorum superficialis,
pass to the middle phalanx of digits 2-5. Whereas FDP, flexor digitorum profundus, pass
to the distal phalanx of digits 2-5. So there's an important arrangement here that
we need to observe. As the tendons or flexor digitorum superficialis pass to the middle
phalanx, the tendons actually split and we can see that here. Here, we can see the
tendon of FDS passing towards the middle phalanx and its tendons splitting. See
it here? We can also see it happening here. See the tendons splitting into 2 as they
go in to touch to the middle phalanx. We can see again here once these tendons
are actually being reflected somewhat. So the tendon of flex digitorum superficialis
here and we can see this actually splits, one going down onto this lateral side and
one just going down this medial side. It's a little bit covered by these, the tendon
of flexor digitorum profundus. The tendon of flexor digitorum profundus as we
can see passes deep through this split. So as the tendon of flexor digitorum
superficialis split, so the deeper tendon of flexor digitorum profundus pass through
this split as it pass to the distal phalanx. And this is a really important arrangement.
02:18
We can see again here, flexor digitorum profundus is passing deep to flexor digitorum
superficialis. And then as it splits, the tendon here is splitting FDP passes deep to it.
02:32
And this enables the tendon of FDP to pass to the distal phalanx. We also have some
vincula tendinum. We have two of these and these are very small little slips of
tissue and they actually attach the tendons of FDP and FDS to each other and also
to the phalanx. We can see these small little tendinous slips. We can see them
passing down here and here we have a longum and a brevia. We have a long one
and we have a short one and these are important in connecting those 2 tendons
to the tendinous sheaths and also in permitting some microcirculation. So these
carry some micro blood vessels to the tendons for that blood supply. So they're
really important in connecting the tendons to each other and also to the phalanges
and also permitting some microcirculation so the tendons can receive that oxygen
and nutrients. So these muscles are capable of working across 2 different joints.
03:43
We have a lumbrical here. We have another lumbrical here, are 2 lateral unipennate
lumbricals. And then we have 2 bipennate lumbricals. We can see we have 1 here
and we have 1 here. So we have 4 lumbricals together. Notice how they all originate
from the tendon of flexor digitorum profundus and they don't work on the thumb,
they don't work on the first digits or any associated with digits 2, 3, 4, and 5. So if we
have a look, we can see lumbricals 1 and 2. These originating from the lateral
2 tendons of FDP and these are unipennate ones, I indicate it. And then we have
lumbricals 3 and 4 and they're originating from the medial 2 tendons of FDP and these
are bipennate. They insert onto the lateral surface of the extensor expansions, as I
mention, of the digits 2 and 5. So they don't work on the thumb, just digits 2-5. The
lumbricals 1 and 2, the lateral 2 lumbricals, are innovated by the median nerve
whereas the lumbricals 3 and 4 associate with the medial tendons of FDP are
innovated by the ulnar nerve. So we can see the lumbricals have a different innovation,
a different nerve supply. The function of these lumbricals is important because they
can both flex and extend different joints. So they can flex the metacarpophalangeal
joint, the joint between the phalanges and the metacarpals, so they can flex that
joint. The phalanges here and the metacarpals, they can flex that joint. And they
are also capable of extending the interphalangeal joints. So they're capable of flexing
that joint but also extending the interphalangeal joint. And that is because of their
position. They run anterior to the metacarpophalangeal joint so they can flex it
and by passing to the extensor expansion, they're running posterior to the
interphalangeal joints. So contraction of these muscles allows flexion of that joint,
the metacarpophalangeal and extension of the interphalangeal joint. And these
position here is important if you're holding a pencil if you're about to write. So these
muscles are important for the digits to assume complex positions. Now let's carry on
looking at a series of short muscles, and these are known as your interossei muscles.
06:22
We have 2 different types of interossei muscles. We have dorsal interossei positioned
on the dorsal aspect of the hand and we have palmar interossei muscles positioned
on the palmar surface. Here, we can see the dorsal interosseous muscles. We have
4 of them. We can see 1, 2, 3, 4 and we can see these have 2 heads. They're
running from the adjacent surfaces of all of the metacarpals. So we can see the dorsal
interosseous here is running from the medial surface of the 1st metacarpal and the
lateral surface of the metacarpal here at the 2nd metacarpal. And we have similar
arrangements. And these are passing towards the extensor expansion, those
extensor hoods over the digits. And then we have the palmar interossei. These
are just running from one of the metacarpal surfaces and we can see they're
coming from digits 2, they're coming from digits 4, and coming from digit 5. Digit 3
does not have an attachment of these interossei muscles. The interossei muscles
do not attach. So we can see that these muscles are going to be associated with
abducting and adducting the fingers. We can see the dorsal interossei are coming
from the dorsal sides of all the metacarpals, these are bipennate muscles. And the
palmar interossei, as I said, come from the palmar sides of metacarpals 2, 4, and 5.
08:02
They insert on to the base of the proximal phalanges and also the extensor
expansions. The nerve supply for these interossei is by the ulnar nerve, the deep
branch. And the dorsal interossei are associated with abducting digits 2-4. Palmar
interossei are associated with adducting digits 2, 4, and 5 this time towards the axial
line. I've put that here towards the axial line and away from the axial line. What
does that mean? Well, if you imagine the axial line is running down in line with the
middle finger, so an axial line is running down here. This is the line at which these
fingers are going to be abducted or adducted. And we can see that with contraction
of these muscles we can put the muscles in cartoon form here. With this axial line,
we can see that the dorsal interossei are going to pull the fingers away from this
axial line. So these dorsal interossei can pull away. This dorsal interossei can pull this
middle finger away. It can also, because we have the dorsal interossei on the other
side, abduct it the other way. For the fingers, we don't talk about abduction and
adduction as moving them towards the midline of the body. We talk about moving
away from this axial line. Therefore, the middle finger can both abduct this way
and it can abduct that way. Whereas the other fingers will all abduct away from
this axial line like that. The middle finger can abduct away either side. If we look
at the palmar interossei, then we look at adducting, so palmar interossei adducting,
and they are going to draw the fingers towards the middle finger, towards the axial
line. So we can see that this interossei will move across, this interossei will move
across, this interossei will also move across. So we've got our middle finger. We can
adduct here, we can adduct here, and we can adduct here. So all the fingers are
together. Don't forget we have adductor pollicis so we can move the thumb across.
10:18
It doesn't need an interosseous muscle. So here we can see the origins and insertions
of these muscles. The easy way to remember the function is for the dorsal interossei
to use the D from dorsal and the AB, so you can have DAB, dorsal interossei abduct.
10:36
And you can have PAD, using the P from palmar interossei pad as the palmar interossei
adduct. So in this lecture, we've looked to the dorsal aspect of the hand, we've
looked at the extrinsic extensor tendons and tendinous sheath. We've looked at
extensor expansions and the anatomical snuffbox, its boundaries and contents.
10:58
We then looked at the palmar aspect, we looked to the carpal tunnel and the ulna
canal. The boundaries and contents. We then looked at compartments, central
hypothenar, thenar, adductor, and interosseous. And we looked to the muscles
within each of the compartments. And then we looked to the extrinsic flexor tendons.