00:00
Remember, we discussed about the
brachial plexus in the morning,
likewise a few things about the lumbar plexus,
lumbar and lumbosacral plexus.
00:12
Who knows about the lumbar,
lumbosacral plexus?
Tell me anything.
What are the nerves, nerve roots?
Where do they come?
Where do they go?
That's sacral. Sorry,
it’s L3 down to S2.
00:27
Anything before that, L1?
What happens to L1?
L1, L2, L3, L4,
L5, S1, S2, S3,
nerves just coming off this
are called the lumbar plexus.
00:51
Nerves coming off this are
called the sacral plexus,
and coming off both of them
is the lumbosacral plexus.
00:58
You don't have
to stand up.
01:02
If you remember your anatomy up to the umbilicus,
that corresponds to T10.
01:09
Then slightly lower
down is T11, T12.
01:13
What is Ll?
What are their roots?
Can you think of any
nerve root of Ll?
What about the sensation
to the groin?
Yes, your ilioinguinal nerve,
that's the L1,
ilioinguinal, iliohypogastric,
iliohypogastric.
01:43
Then you mentioned the
genitofemoral nerve,
this L1, genitofemoral
nerves from L1, L2.
01:58
Is there anything else
you can think of?
Have you come across a condition
called meralgia paresthetica?
Yeah. So that also usually
comes from L2, L3.
02:12
L2, L3, it runs under the anterior
superior iliac spine.
02:17
What's that?
Yeah. You get compression, and ascites,
pregnancy, or anything compressing on it
and cause altered sensation to the
lateral aspect of the thigh.
02:27
So, that is lateral cutaneous
nerve of the thigh.
02:36
Yes. That's right,
usually L1, L2.
02:44
These are the important nerves
which are all cutaneous.
02:51
Your genitofemoral nerve
has two branches,
the genital branch or genitofemoral
and the femoral branch.
02:57
The genital branch or genitofemoral is the
one which supplies the scrotum
or the external genitalia
in females.
03:03
The femoral branch is the one which
supplies sensation over the
anterior aspect of the
femoral triangle.
03:11
So that's why when you are testing
for dermatome, that's the Ll.
03:16
Now, we'll go
to mixed nerves.
03:19
That is L1, L2, L3, sorry
L1, L2 supplying.
03:23
Then from L2, L3, L4, those
unite and it forms
an anterior division and
a posterior division.
03:35
Anterior division is the one which
forms the obturator nerve.
03:39
Posterior division is the one which
forms the femoral nerve.
03:42
So, anterior division is the nerve
to the anterior compartment.
03:49
Posterior division is a nerve
to the middle compartment.
03:53
So that is L2, L3, L4. What's next?
Okay, Hannah.
04:05
Posterior branch.
04:05
Posterior femoral and it
branches to obturator.
04:10
So the anterior branches along
the middle compartment?
That’s right,
middle compartment
and the posterior one is femoral which
is supplying this compartment.
04:16
So, is it medial?
Is it posterior?
Okay, what else is there?
Then anything else?
Sciatic.
04:27
Sciatic, sciatic is
L4, L5, S1, S2, S3.
04:36
We’ll discuss sciatic in a
bit of detail in a minute.
04:39
But for now, just
remember this.
04:45
Sciatic,
anything else?
A couple of other
important nerves?
You have the superior and
the inferior gluteal nerves.
04:55
Superior gluteal nerve
comes off 4, 5, S1.
05:01
Inferior gluteal nerve comes
off L5, S1, S2.
05:06
You don't have to know
the root values.
05:08
But just remember
from these plexus,
you have the inferior and
the superior gluteal nerve
supplying all the
gluteus muscles.
05:15
The final which will be your
S2, S3 for pudendal nerve.
05:24
Pudendal, what does
it supply?
External urethral sphincter, pelvic diaphragm,
levator ani those sort of areas.
05:39
So, S1, S2, S3, S4 keeps your
rectum of the floor.
05:45
S2, S3 is always pudendal.
That’s your essentially lumbosacral plexus.
05:52
Now, if you go
back to the leg,
I'm just thinking how to do it quickly
without you standing for too long.
06:00
I'll just go through theory a bit more
and then you can stand up.
06:03
We've done the
anterior compartment,
medial compartment,
posterior compartment.
06:08
What are the muscles in the
posterior compartment?
Semimembranosus,
semimembranosus,
semitendinosus,
and biceps femoris.
06:16
So on the lateral side,
you have biceps femoris
and on the
medial side,
it’s semimembranosus,
semitendinosus
Nerve supply:
sciatic.
06:25
Now, the biceps
femoris, bi, two,
biceps femoris has got a
long head and a short head,
the long head of biceps femoris and
the short head of biceps femoris.
06:35
Usually, it is by the sciatic, but occasionally
the short head of biceps femoris
comes from the
tibial nerve.
06:44
Sciatic nerve, I think I won't
ask you the sense.
06:49
Sciatic nerve comes down right
in the midline of the leg,
comes up to the top of
the popliteal fossa,
and divides into tibial
and common peroneal.
07:11
Similar to your radial
nerve in the arm
which supplies the anterior
and posterior aspect,
the sciatic nerve supplies the anterior
and posterior aspect of the leg.
07:23
One important thing you have
to get as a concept is
your femoral nerve supplies
nothing below the knee.
07:32
Everything below the knee,
ankle, foot, it's all from the sciatic.
07:37
That's why it's such
an important nerve.
07:39
Femoral nerve’s only job
is to supply the hip flexors,
so iliacus, psoas, pectineus,
then the anterior compartment of the thigh
which extends to the knee, that's it.
07:51
Then it's cutaneous,
okay?
Everything to do with the rest of the
knee and the foot, sciatic.
08:04
Popliteal fossa.
08:09
Maybe one more time, we will be
able to finish it off, yeah.
08:13
Do you mind?
That’s fine.
08:14
Can you turn
around please?
So very quickly, I don't want him
to stand there for too long.
08:19
Very quickly, the popliteal fossa,
boundaries, content,
it’s similar to
the cubital fossa.
08:24
It is quite important. Biceps femoris,
semimembranosus, semitendinosus,
medial head of gastrocnemius,
lateral head of gastrocnemius.
08:33
Just flex, bend
your knee a bit.
08:35
So that's the skin. What else is there,
skin, subcutaneous fat?
That's deeper, but no,
on the skin itself.
08:47
Remember, we discussed
the cubital fossa.
08:49
I said you have median cubital
vein, subcutaneous nerves.
08:53
Anything can you think
of here on a skin?
I'm sure you
can think of-.
08:56
Cutaneous nerves.
What cutaneous nerves?
I'm sure you
can think of-.
08:56
Cutaneous nerves.
What cutaneous nerves?
Sural nerve, sural nerve,
you have the sural nerve.
09:02
Sural nerve comes off the cutaneous
and lies in the midline.
09:05
And what vein?
You know this.
09:08
Not popliteal vein,
short saphenous vein.
09:13
Yeah, you have a short
saphenous vein
starting from the lateral arch
of the foot coming this way
along with the sural nerve and
emptying the popliteal vein here.
09:25
So they are all on the
surface of the skin,
on the skin and the
popliteal fossa.
09:32
Now, if you reflect
the surface,
what is the first thing
you come across?
Imagine, you reflect
the skin.
09:40
What is the first anatomical structure,
nerve, artery, or vein?
Nerve, no, you come across
the tibial nerve first.
09:49
Then you have the common
peroneal nerve
which would have just sort
of given off there,
common peroneal nerve, also called
the common fibular nerve.
09:59
Now it’s called the common fibular nerve
or the common peroneal nerve.
10:03
Below that you come across
the popliteal vein,
and below that,
popliteal artery.
10:09
So the deepest structure in there.
10:10
There are two
nerves there.
10:11
There’s the tibial nerve and the
common peroneal nerve.
10:14
So superficially, you’ve got sural nerve
but then you’ve got two further deep.
10:18
That’s right. On that note,
I’ll just clarify this.
10:22
The sciatic nerve comes
down here, that way.
10:26
Now, about 5, 6 centimeters
above the joint line,
that's when it
divides into two.
10:31
So sometimes you might not see
the common peroneal nerve
lying there because
it's already gone off.
10:35
So you might see only
the tibial nerve.
10:37
Tibial nerve, you'll definitely see
because it is the midline.
10:40
Common peroneal, you might not see
because it might have gone off.
10:43
In your exam, if they ask
about the popliteal fossa,
they are expecting you to know the
tibial nerve, the most superficial.
10:50
Deeper to that is the popliteal vein.
Deepest is popliteal artery.
10:55
What’s the floor of
the popliteal fossa?
Remember, you have a
muscle here, brachialis.
11:06
Can you think of
a muscle there?
Popliteus, popliteus, okay?
So simple, popliteus.
11:11
Then you have the capsule
of the knee joint. That's it.
11:17
Just turn around for a minute
please, a little bit.
11:19
So this is your common
peroneal nerve,
winding around the neck of the fibula
or the common fibular nerve.
11:26
This is the one which divides into
superficial peroneal and deep peroneal.
11:31
Superficial peroneal supplies the
lateral compartment of the leg.
11:38
Deep peroneal supplies the anterior
compartment of the leg.
11:42
These are the
two nerves.
11:44
Your tibial nerve
at the back
supplies all the muscles in
the posterior compartment.
11:52
Do you mind just turning around
one more time?
So, that's your deep
peroneal nerve.
12:01
Just think about what you think the function
of the deep peroneal nerve is then.
12:04
So, it is to dorsiflex
the foot.
12:07
What’s the other action
of the deep peroneal?
Evert. Evert the foot,
correct.
12:13
Similar to what
we discussed,
we spent a lot of time
in the upper limb.
12:18
Likewise, this part of anatomy
is very important. It comes up.
12:21
Inversion of the foot,
eversion of the foot,
at what joint does it happen,
which nerve does all that.
12:26
So you need to just
concentrate on this bit.
12:28
So your deep peroneal nerve supplies
the anterior compartment of the leg.
12:33
What are the muscles in the anterior
compartment of the leg here?
Tibialis anterior,
tibialis anterior,
extensor hallucis longus,
extensor hallucis longus,
peroneus tertius,
peroneus tertius
One more, extensor
digitorum longus.
12:47
So, if his deep peroneal nerve is injured,
none of them will work.
12:58
Patient is going to have a foot drop
because the dorsiflexors are not working.
13:05
But the plantar flexors are working because
that is supplied through the back.
13:09
Will the patient be able
to evert the foot?
Evert? Evert.
Why not?
You can invert the foot,
but what about eversion?
You're right.
Common peroneal does both.
13:33
But the deep peroneal
does only inversion.
13:36
So if you have a common peroneal
nerve injury here, you're right.
13:40
No dorsiflexion, inversion is lost,
eversion is lost.
13:46
But if you have a deep peroneal
nerve injury there,
you have dorsiflexion is lost,
inversion is lost,
but the eversion is preserved because
the superficial peroneal nerve
will help in the eversion
and it's vice versa.
14:00
So if you have only that nerve injured,
only the eversion is lost.
14:05
So if you get a clinical scenario whereby
they say everything is okay
except that patient is unable
to evert the foot,
then it is very specific for superficial peroneal
or superficial fibular nerve.
14:18
So, the two muscles in the lateral
compartment of the leg are
peroneus longus,
peroneus brevis.
14:26
For the last time, if you
would turn around.