00:02
So this brings us to
the leg which again,
you're probably used
to seeing arm and leg,
but we know arm is only
a part of the upper limbs.
00:10
Similarly,
leg is only a part of the lower limb,
just the part between
the knee and the foot.
00:17
And again,
there should be some similarities
coming to mind when we
talked about the forearm
because this is the lower
limb equivalent of the forearm.
00:25
So instead of one bone,
we have two,
one's a bit smaller
than the other.
00:30
The small one
laterally is the fibula.
00:34
It has a head and a neck.
00:37
And at the distal end,
there's a bump or malleolus.
00:41
And because it's the lateral bone,
it's called the lateral malleolus.
00:45
And when you reach
down towards your ankle,
and you feel those two
bumps on either side,
that's what you're feeling the
lateral malleolus of the fibula.
00:53
The larger bone more
immediately is the tibia.
00:58
And it has a long
anterior crest,
you can usually palpate
or more likely run into
something hard in the
dark and hit your shin.
01:06
And that anterior crest
is pretty vulnerable,
because there's not a lot
of muscles directly over it.
01:12
And that's why when
you hit your shin bone,
that's where you tend to hit it.
01:17
And it's bumped at the distal
end is called the medial malleolus.
01:21
So when you feel that bump
on either side of your ankle,
they're actually on
two different bones,
the lateral malleolus
on the fibula,
and the medial
malleolus on the tibia.
01:32
And there are these
interosseous borders
very similar to what happened
in the radius and the ulna.
01:38
If we look at the
proximal end of that tibia,
we see there's a lateral
condyle and a medial condyle.
01:47
And of little space in between
between the two would
be called intercondylar,
so little on intercondylar
eminence there.
01:55
Very similar, again,
to the joints of the upper limb.
02:00
So we'll put those bones
back together as they like to be.
02:04
And we see we have a
superior tibiofibular joint
and an inferior
tibiofibular joint.
02:11
Again, all of this is very,
very similar
if you've already seen the form.
02:17
Generally speaking,
the movements are a little confusing
when we talk about the
movements down at the ankle,
and the muscles that
we're going to talk about
what they do don't
really fit our typical
descriptions with
flexion and extension.
02:32
So the situation here
is a little different.
02:35
And you're just gonna
have to bear with the fact
that these terms really
only exist down here.
02:40
So what I'm saying is
when the foot is moved,
such that the toes lift up,
that's something
called dorsiflexion.
02:49
And that's something
that we're going to see
called the deep fibular
nerve comes into play,
but the opposite is also called flexion,
unfortunately,
so moving the other ways,
something called plantar flexion.
03:02
So pointing the toes
up is dorsiflexion,
pointing them down,
is plantar flexion.
03:07
It's kind of funny because
we're like wait flexion and flexion.
03:10
But we throw in
these descriptors,
dorsi versus plantar
to help us understand.
03:15
Unfortunately,
that's just how they're named in this area.
03:19
That said,
when we're talking about the
anterior compartment
of the leg muscles,
generally they're going to be
the toe razors or dorsiflexors.
03:29
And there's going to be
a nerve we're going to see
called the deep fibular nerve
that takes care of things here.
03:35
So we have the tibialis anterior,
great name.
03:40
We just said the tibia is here
and we're talking about
the anterior compartment.
03:44
We have extensor
digitorum longus.
03:48
Right now, you're probably
thinking that sounds very similar.
03:50
So why don't we just
call dorsiflexion extension
if we're calling these
muscles extensors?
Well, we just we just don't unfortunately,
I'm sorry.
04:00
But it tells you a little
bit about what's going on.
04:03
Digitorum in this sense,
not four fingers, but for toes.
04:08
We also have extensor hallucis
longus and fibularis tertius.
04:13
Fibularis over on
the fibular side.
04:16
But extensor hallucis longus,
hallicus a new one.
04:19
Hallucis is our word for big toe
just like we had
pollicis for thumb
and lot of similarities here.
04:28
If we swing around to
the lateral compartment,
these do another unique
movement here at a different
ankle joint called the
subtalar joint we'll see.
04:37
And that's where
we move the outside
of the foot up something
called eversion.
04:42
And we're going to
see there's a nerve
called the superficial
fibular nerve
that takes care of things here.
04:48
So here we have
the fibularis brevis.
04:52
And we can see that
it's going down into
the foot to carry out
that eversion action
and a fibularis longus
which also is going down
into the foot to carry
out those actions.
05:02
And fibularis is a great name
because we said the fibula
is the lateral bone and we're
in the lateral compartment.
05:10
If we go to the
posterior compartment,
we're going to see that
there are some superficial
and deep layering
to the muscles here.
05:17
But they're generally
going to be the opposite
of the anterior compartment,
as is usually the case.
05:21
So they're going
to do plantar flexion
or basically point
the toes downward.
05:26
And they're going
to be innervated
by something called
the tibial nerve.
05:31
The first thing we're going to see
something called the gastrocnemius.
05:35
Gastrocnemius,
it's going to have two heads,
a medial head
and a lateral head.
05:42
And we can see
that it has this really
thick tendon called
the calcaneal tendon,
because that's the bone
in the foot it's attaching to.
05:49
But more commonly referred
to as the Achilles tendon,
because you've probably
heard of the Achilles tendon
and the story of Achilles
and being dipped by the heel,
and that was the
vulnerable part.
06:00
Well, here we see it's
a really thick tendon.
06:03
And it's attached to these
muscles that you probably
have heard before
called as calf muscles.
06:09
And the first one we're
seeing is the gastrocnemius,
really strong, thick tendon,
a lot of stress is put on it.
06:15
That's why it's
so big and thick.
06:19
But if we remove it,
we see a flat muscle called the soleus.
06:24
Almost like if you've seen,
like Dover sole, the flat fish,
it's kind of like a sole,
like a very thin flat muscle.
06:33
And unlike the gastrocnemius,
which also crosses the knee,
and therefore has an action
of a little bit of knee flexion,
the soleus acts purely
as a plantar flexor.
06:47
And actually, that's why if
you've kind of noticed some
soreness in your calves,
when you go up hills, for example.
06:53
If you have your knees bent,
the gastrocnemius
because it's crossing
the knee joint can't
actually do plantar flexion.
07:01
So if your knees
are kind of bent,
such as like,
if you're going up a steep hill,
it's actually all your soleus.
07:07
So that calf soreness
is actually deeper,
and it's not your gastrocnemius,
it's your soleus.
07:14
We also have this
tiny muscle with a
really long tendon
called the plantaris.
07:20
And that is sort of the
equivalent of our palmaris longus
in the sense that we
don't really need it.
07:25
But if we needed a
long tendon for a surgery
to replace something
more useful elsewhere,
we can take that out and not
really have any consequences.
07:36
Now we'll go into the
deep compartment.
07:39
And that's where we're
going to find that little
unlocking muscle of the
knee called the popliteus.
07:44
And the tibialis posterior,
which again,
we can see that tendon
going all the way
down into the foot.
07:51
We also have the
flexor hallucis longus.
07:54
Again, hallucis,
meaning our toe or big toe.
08:00
And we can see that going all
the way down to the big toe as well.
08:03
Flexor digitorum longus,
And again,
this is all equivalent to the stuff
that we saw in the forearm,
going down to the digits.
08:12
In this case, the toes,
all very similar
to the stuff we saw
already in the hand.
08:20
So now let's look at the
arterial supply of the leg.
08:25
We already said the femoral
artery has to go behind
the knee so that it
doesn't get so compressed,
and when it goes
behind the knee,
it changes named
to the popliteal artery.
08:35
Then we're going to
have these branches
such as the
anterior tibial artery,
as the name implies,
it's going to go
take care of the
anterior compartment.
08:43
We're gonna have the
posterior tibial artery
taking care of the
posterior compartment.
08:47
And a fibular artery.
08:49
Again, fibular,
the fibula is on the lateral side,
that's going to take care
of our lateral compartment.
08:56
Now let's take a look
at the nerves of the leg.
08:59
That big prominent nerve
we saw on the posterior thigh
called the sciatic nerve is
eventually going to branch
into a posterior tibial
nerve and take care
of the muscles of the
posterior compartment.
09:11
And then a common fibular
nerve that is going to branch again,
into a deep fibular nerve going
over to the anterior compartment,
and a superficial fibular nerve
taking care of the
lateral compartment.