Test your understanding with 10 random multiple-choice questions from the question bank.
A minor mistake in the video: Superior and Inferior gluteal nerves come from the posterior divisions of L4-S1, not the anterior as shown in the scheme (apologies for this mistake).
Introduction
0:06
alright so in this video we’re going to
0:07
talk about the sacral plexus we already
0:10
talked about the cervical plexus we
0:11
talked about the brachial plexus we
0:13
talked about the lumbar plexus the last
0:16
large plexus we have now is the sacral
0:18
plexus so let’s go ahead and get started
0:20
so first we’re going to go through the
0:22
topography just talk a little bit about
0:24
which nerves feed into the sacral plexus
0:27
then after that we’re going to make a
0:29
scheme of the sacral plexus and to make
0:32
this as easy as possible to understand
0:34
and remember we’re going to draw the
0:36
general outline first
0:38
then we’re going to go ahead and divide
0:40
the nerves into long branches and short
0:43
branches
0:44
and go through each nerve and a little
0:46
bit of clinical importance related to
0:49
those nerves
0:50
and at the end there will be a little
0:51
quiz
Topography of Sacral Plexus
0:52
so let’s go ahead and get started with
0:54
the topography so here we see the spinal
0:57
nerve within the vertebral canal and
1:00
here we see the spinal nerve leaving the
1:02
intervertebral foramen
1:04
so there will be one spinal nerve
1:06
leaving on each side they’re paired
1:09
to be specific though we’re not really
1:11
talking about the whole spinal nerve
1:13
right we’re actually talking about the
1:15
anterior branch of the spinal nerve
1:18
because the anterior branch is what
1:20
forms all the plexuses that we’ve talked
1:22
about in this series of videos
1:25
alright so the sacral plexus is formed
1:27
from the anterior branches of the spinal
1:30
nerves l4
1:31
l5
1:33
s1 s2 s3 and s4
1:37
alright
1:38
so this is a pretty big plexus one of
1:40
the main nerves that are coming from the
1:42
sacral plexus is the sciatic nerve and
1:45
we’ll talk a little bit about the
1:46
clinical correlation with that so let’s
Scheme of the Sacral Plexus
1:49
go ahead and simplify this drawing what
1:52
i want you to do is to grab a piece of a
1:54
paper and a pen and i want you to draw
1:57
the scheme with me and once you do that
1:59
i promise you will remember this much
2:01
much easier
2:03
alright
2:04
first off we can start by drawing a line
2:06
from l4 all the way down to s3 like you
2:09
see here
2:11
what happens is
Sciatic Nerve
2:12
off from l4
2:14
there’s going to be a division and
2:16
anterior division that are going to
2:18
traverse this way
2:20
on its way down it will pick up a branch
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from l5 it will pick up a branch from s1
2:26
s2 and s3
2:29
another thing that’s going to happen is
2:31
that from l4 same thing another branch
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is going to emerge but this one is going
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to be more posteriorly and same thing it
2:40
will pick up a poster of your branch
2:42
from l5 s1 s2 and s3
2:46
these two nerves are called the tibial
2:49
nerve and the common feebler nerve so
2:52
the tibial nerve comes from the anterior
2:55
division of branches coming from l4 to
2:58
s3
2:59
from the sacral plexus and the common
3:01
feebler nerve come from the posterior
3:04
division of branches coming from l4 to
3:07
s3 from the sacral plexus
3:10
however those two nerves run together in
3:13
a sheath so they go together forming
3:16
this chaotic nerve it’s referred to as
3:19
the largest nerve we have in the body
3:21
it’s about two centimeters in diameter
3:24
what happens is the sciatic nerve is
3:27
going to pass through the greater
3:29
sciatic foramen
3:30
below the piriform muscle
3:32
and then pass between the muscles of the
3:35
posterior thigh and descend distally
3:38
towards the knee
3:39
posterior knee the popliteal fossa
3:43
when it’s at the posterior knee it will
3:46
split into two main branches right and
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this is where the sciatic nerve splits
3:52
into the anterior division also known as
3:54
the tibial nerve and the posterior
3:57
division also known as the common
3:59
feebler nerve
4:00
they’re both going to have a decent
4:02
amount of cutaneous and motor supply so
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for the tibial nerve the tibial nerve
4:08
travels with the posterior tibial artery
4:11
and veins
4:13
they descend between the posterior
4:15
muscles of the cuff
4:17
reaches the sole via the malarial canal
4:20
and then divides into the medial and the
4:23
lateral plantar nerves
4:25
alright so the first branch that i want
4:26
to mention here is the medial cereal
4:29
cutaneous nerve which runs with the
4:31
small saphenous vein
4:34
it lies very superficially under the
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skin and then it joins the lateral
4:39
sterile cutaneous nerve from the common
4:41
fibular nerve to form the sural nerve
4:44
the sural nerve is actually a type of
4:46
somatosensory nerve so it provides
4:49
somatosensory innervation of the calf
4:52
and the lateral side of the heel
4:54
all right other nerves that the t-build
4:57
nerve is going to give off are muscular
4:59
branches which innervates the posterior
5:02
muscles of the calf
5:04
it also gives off the medial plantar
5:07
nerve now this is a special nerve why is
5:09
it special
5:10
it’s special because the medial plantar
5:13
nerve is both a cutaneous and a motor
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nerve
5:17
so by motor fibers it supplies the
5:20
abductor hyalurosis muscle flexor
5:22
hallucis brevis flexor digitorum brevis
5:25
and the first and the second lumbricals
5:28
the sensory fibers are going to supply
5:31
the medial part of the soul and form a
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common plantar digital nerves which
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divides into six digital plantar nerves
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to supply the first second third and
5:42
half of the fourth
5:44
toes
5:45
the tibial nerve is also going to give
5:48
off a lateral plantar nerve which
5:50
travels with the lateral punter archery
5:53
and veins to the fifth toe and innervate
5:56
the quadratus plantaris which remember
5:59
is a muscle that helps with flexion of
6:01
the lateral four digits of the foot
6:04
now
6:05
the lateral plantar nerve is eventually
6:08
going to divide into two branches
6:11
a superficial branch which gives off the
6:14
proper plantar digital nerves for the
6:17
fourth and fifth toe and a d branch
6:20
which travels to the interusae and the
6:22
oblique head of the adductor holsters to
6:25
innervate the abductor digiti minimi
6:28
flexor ddt minimi brevis
6:30
interossei adductor hollisis and the
6:33
lumbricals for the fourth and fifth toes
6:37
all right so that was the tibial nerve
6:39
let’s move on to the common feebler
6:41
nerve
6:42
the common feebler nerve runs obliquely
6:45
along the lateral side of the popliteal
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fossa
6:48
curves around the head of the fibula and
6:51
then it divides into two terminal
6:53
branches
6:54
a superficial fibular nerve and the deep
6:56
fibular nerve
6:58
before we talk about these there are
7:00
some nerves that we should mention
7:02
that has some important innervation for
7:04
the local sensations here
7:06
one of the branches are the articular
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branches which provide somatosensory
7:11
innervation of the knee joints and the
7:14
tibiofibular joints there’s the lateral
7:17
cereal cutaneous nerve which provides
7:19
somatosensory innervation for the
7:21
lateral calf
7:23
and
7:24
remember it also joins the medial cereal
7:26
cutaneous nerve to form the surreal
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nerve alright so now the superficial
7:33
fibular nerve
7:34
this one will run between the fibula and
7:37
the fibularis longus and then continue
7:40
between the fibular muscles
7:42
on its way down it gives off muscular
7:45
branches to innervate the fibular
7:47
muscles
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and then it penetrates the fascia
7:50
reaching the anterior surface and then
7:53
runs superficially on the dorsum of the
7:55
foot
7:56
at this point it gives off the medial
7:59
dorsal cutaneous nerve which splits into
8:02
the dorsal digital nerves
8:04
of the foot to innervate the medial side
8:06
of the first toe
8:08
lateral side of the second toe and the
8:10
medial side of the third toe
8:13
and it gives off the intermediate dorsal
8:16
cutaneous nerve which splits into the
8:18
dorsal digital nerves of the foot to
8:21
innervate the lateral side of the third
8:23
toe the whole fourth toe and the medial
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side of the fifth toe
8:28
all right we done the superficial
8:31
fibular nerve let’s talk about the d
8:33
feeble nerve
8:34
the d fibular nerve will run along the
8:37
anterior side of the interserious
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membrane of the leg
8:41
then it follows the anterior tibial
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artery and veins to travel under the
8:47
extensor retinoclum and then it emerges
8:50
on the surface of the first interdigital
8:53
space
8:54
it gives off the lateral dorsal digital
8:57
nerves of the toe which provides tomato
8:59
sensory innervation for the lateral side
9:01
of the first toe
9:03
and a medial dorsal digital nerves of
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the toe which provides somatosensory
9:08
innervation of the medial side of the
9:10
second toe
9:12
alright it’s a large nerve i advise
9:14
y’all to draw it a couple of times it
9:16
helps
9:17
now there’s actually one thing i forgot
9:20
to mention about it it’s that the
9:22
sciatic nerve has also muscular branches
9:25
that innervates the posterior thigh so
9:28
the biceps femoris
9:30
semitendinosus semimembranosus and the
9:33
part of the adductor magnus
9:35
and it has articular branches which
9:38
provide a partial somatosensory
9:40
innervation of the hip joints
9:43
if there’s a damage to the tibial nerve
9:46
usually it occurs in the male canal and
9:49
can result from cut wounds ankle
9:51
fractures and incorrectly applied
9:53
plasters
9:55
it usually presents as impaired plantar
9:58
flexion which is an inability to stand
10:00
on a tip toes due to an impaired
10:03
function of the triceps surah and the
10:07
ankle jerk reflex is usually absent
10:10
due to the predominance of the
10:12
unantagonized dorsal flexion of the
10:14
tibialis anterior the heel is the first
10:17
part of the foot that touches the ground
10:20
while walking so this results in a
10:22
syndrome called clubfoot or pescalcones
10:26
the fibular nerve however is covered
10:28
only by skin where it lies near the head
10:31
of the fibula
10:32
in this location the nerve is most
10:34
vulnerable to trauma and also
10:36
compression from incorrectly applied
10:38
casts this location and sprains of the
10:41
knee can also cause harm to this nerve
10:44
and if there’s a damage to the fibular
10:46
nerve the anterior muscles of the leg
10:49
become impaired resulting in a flapping
10:52
foot
10:53
and an inability to stand on the heels
10:56
another thing that happens is that the
10:58
arches of the foot gradually
11:00
deteriorates due to the dysfunction of
11:02
the fibularis longus
11:04
okay so that’s the sciatic nerve finally
Posterior Cutaneous Nerve of the Thigh
11:08
the other nerve that’s generally
11:10
mentioned on the long branch category is
11:12
the posterior cutaneous nerve of the
11:15
thigh
11:16
the posterior cutaneous nerve of the
11:18
thigh come from s1
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on its way down it picks up a branch
11:23
from s2 and it picks up a branch from s3
11:27
this one exits the pelvic cavity through
11:29
the greater sciatic foramen below the
11:32
piriform muscle as well
11:34
and descends under the gluteus maximus
11:37
to the posterior surface of the thigh to
11:40
provide somatosensory innervation to the
11:42
dorsal thigh
11:44
then more distally it also supplies the
11:46
skin over the property alfossa
11:49
now what happens is is that it’s going
11:52
to give off the inferior colonial nerve
11:55
which provides somatosensory innervation
11:57
to the distal part of the gluteus region
12:00
and the perineal branches which provide
12:03
somatosensory innervation to the
12:05
perineal skin
Pudendal Nerve
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alright so that was all the long
12:09
branches the branches that kind of
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extend a little further from the sacral
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plexus
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now let’s go over and do the nerves that
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are considered short the short branches
12:20
the short branches the first one that
12:22
we’re going to mention is called the
12:24
pudendal nerve the potential nerve is
12:27
going to come from s2
12:29
and on its way it’s going to pick up a
12:31
branch from s3 as well as a branch from
12:34
s4
12:36
the potential nerve runs through the
12:38
infra-pediform foramen with the internal
12:41
potential artery and veins
12:44
then it turns around the ischial spine
12:47
into the lester sciatic foramen
12:49
enters the ischioanal
12:52
and passes inside the pudendal canal to
12:55
reach the external genital organs
12:58
so essentially this one will end up in
13:00
the genital organs it will terminate as
13:03
either the dorsal nerve of the penis or
13:06
the dorsal nerve of the clitoris to
13:08
supply the skin of the penis or clitoris
13:12
there are three main side branches that
13:14
we should be aware of for this nerve the
13:16
first one is the inferior rectal
13:19
branches which innervate the external
13:22
anal sphincter and provide somatosensory
13:25
innervation to the skin around the
13:28
intergluteal crests
13:30
the second ones are the perineal nerves
13:33
which supplies all the muscles of the
13:35
perineum
13:36
and they also supply the skin of the
13:38
perineum and terminates as the posterior
13:42
scrotal nerves for men or the posterior
13:46
labial nerves for female to supply the
13:48
skin of the external genitals
13:51
the third nerve that we should be aware
13:53
of is the anocoxide nerve which supply
13:56
the skin in the region of the coccygeal
13:58
bone
13:59
alright so that was the perineal nerves
Muscular Nerves
14:03
other nerves we have are so-called
14:05
muscular nerves
14:06
so we’re going to have nerves coming off
14:09
the l5 s1 and s2 that are going to
14:12
supply the obturator
14:15
and the superior gameless muscles so
14:18
nerve of the obturator internals and
14:20
superior gameless muscles why is it
14:23
important because these are also deep
14:25
muscles they provide lateral rotation of
14:28
the hip or external rotation of the hip
14:31
okay so that’s going to be this nerve
14:34
now there’s going to be another one
14:36
coming off s1 and s2 is a nerve for the
14:40
performance muscle which is also a deep
14:43
muscle giving external rotation at the
14:45
hip joints
14:46
all right
Superior Gluteal Nerve
14:47
the last two nerves are thankfully easy
14:50
ones too
14:52
they’re called the superior gluteal
14:54
nerve and the inferior gluteal nerve
14:57
the superior gluteal nerve come from the
15:00
anterior of your branches of l4 l5 and
15:03
s1
15:04
and this one is going to run through the
15:06
suprapedophone foramen to innervate the
15:09
gluteus medius gluteus minimus and the
15:12
tensor fasciae latae and these are
15:14
important muscles they’re abductors so
15:16
if there’s a damage or compression of
15:19
the superior gluteal nerve usually it
15:22
leads to impairment in abduction of the
15:25
hip joints
15:26
walking and standing on one foot can
15:28
become difficult and a patients develop
15:31
a duck-like gate
15:33
to prove this you can check for
15:35
trendlenberg’s sign
15:37
it’s usually positive in damage to the
15:39
superior gluteal nerve it’s
15:42
it is demonstrated by asking the patient
15:44
to stand on the affected leg
15:47
the unsupported side of the pelvis will
15:49
drop lower than the side the patient is
15:52
standing on
Inferior Gluteal Nerve
15:53
the other one is the inferior gluteal
15:56
nerve and this one is going to come from
15:58
the anterior branches of l5
16:02
s1 and s2
16:04
this one will run through the
16:05
infrapediphorn
16:07
to innervate the gluteus maximus now
16:10
gluteus maximus is important because it
16:12
provides two functions one function is
16:15
that it’s going to play a role within
16:16
extension at the hip joints and it’s
16:19
also going to play a role within
16:20
external rotation at the hip
16:22
so a paresis of the inferior gluteal
16:25
nerve usually results from impaired
16:28
function of the gluteus maximus limiting
16:30
the extension at the hip joint and this
16:33
usually causes it to be difficult to
16:34
walk upstairs
16:36
alright so that really sums up the
16:38
sacral plexus
QUIZ
16:40
now what i’m gonna do is i’m going to
16:42
give you all an easy quiz
16:44
i’m going to change all the labels to
16:46
numbers and put the names in a table
16:50
then i’m going to make all the names
16:52
disappear and can you from the beginning
16:55
tell me what is the name of number one
16:57
what is the name of number two what does
16:59
number three supply and what does number
17:01
four supply if you can do that then
17:03
you’ve got a good grasp of this topic
17:06
there you have it my friends thank you
17:07
so much for watching another one of my
17:09
videos if you enjoyed learn something
17:11
from it please remember to like comment
17:13
your favorite moment subscribe turn on
17:16
those notifications if you’re looking
17:18
for other ways to support go ahead and
17:19
check the link in the description box
17:22
see you next time peace
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