Okay, so this is a tutorial on the muscles of the gluteal region and the muscles of the
thigh.
So I'm going to cover quite a lot of muscles here, but I'm not going to go to a huge amount
of detail because I've done that in some other individual tutorials.
So the gluteal region is this region here between the iliac crest and the gluteal fold,
so the fold of the buttock.
So it's helpful to think of the gluteal region in terms of deep and superficial muscles.
So the deep muscles are small, little muscles and are mainly lateral rotators of the hip.
And then you've got the large, powerful superficial group, which you can see here, which are mainly
extensors and abductors of the hip, the femur of the hip.
So you've got three muscles in the superficial region.
You've got this muscle here which is the gluteus maximus.
This muscle is innervated by the inferior gluteal nerve.
Next you've got the gluteus medius, which lies just underneath.
You can see this fan-shaped muscle here.
This abducts the femur.
And we've got the minimus, which lies underneath.
That is also an abductor.
It works together with the gluteus medius.
So those are the three gluteus muscles -- gluteus maximus, medius and minimus.
And then you've got this muscle here, the tensor fasciae latae muscle.
This muscle inserts onto this band of fascia, the iliotibial tract.
What this muscle does is it stabilizes the knee in extension.
So that's the tensor fasciae latae muscle.
You can see the spelling here.
So those are the four muscles of the superficial group in the gluteal region.
Next, you can see these muscles underneath, which are the muscles of the deep layers.
These are mainly lateral rotators of the femur.
So I'm just going to talk you through these muscles from superior to inferior.
The top muscle here is the piriformis muscle.
This muscle originates on the sacrum.
So if we just fade away the other muscles, you can see where it originates.
You can see it's on this anterolateral surface of the sacrum and it inserts onto the femur,
so it laterally rotates the femur.
An important thing I want to point out is the greater sciatic foramen.
If you look at this side, you've got the greater sciatic notch in the pelvis and you've got
this little bump here, which is the ischial spine of the pelvic bone.
So you've got a ligament which runs from the ischial spine to the sacrum and that's called
the sacrospinous ligament.
So above the sacrospinous ligament, you've got the greater sciatic foramen.
You've also got another ligament which lies posteriorly to the sacrospinous ligament called
the sacrotuberous ligament, which is oriented more vertically.
So the greater sciatic foramen is this space between the greater sciatic notch and the
sacrospinous and sacrotuberous ligaments.
You can see that here.
I'll just rotate the model over and show a little bit more clearly here.
So this is the sacrospinous ligament running horizontally from the ischial spine to the
sacrum and you've got the sacrotuberous ligament, which runs vertically from the ischial tuberosity
to the sacrum.
That's why it's called sacrotuberous.
It refers to the ischial tuberosity, 'sacrotuberous'.
The reason I mention this is that the piriformis run through this greater sciatic foramen and
there's two little gaps above and below the piriformis.
So above the piriformis, you've got some vessels and nerves that pass through and below the
piriformis, you've got vessels and nerves that pass through.
Importantly, below the piriformis, you get the sciatic nerve and above, you get the superior
gluteal nerve and vessels.
So you can see the sciatic nerve emerging below the piriformis in the greater sciatic
foramen.
It's above the sacrospinous ligament, but below the piriformis.
And you've got the superior gluteal nerve coming above the piriformis.
So just below the piriformis muscle, you've got this muscle called the gemellus superior.
You've got the gemellus inferior below here.
Between, you've got this muscle called the obturator internus muscle.
So the obturator internus muscle actually sits -- I'll just get rid of these muscles
and ligament.
So this is the obturator internus muscle which sits on the medial surface of the obturator
membrane.
I've just isolated this muscle so you can take a look at it.
This is the obturator foramen and you've got a membrane which covers it.
So on the lateral surface, on the external surface, you've got a muscle called the obturator
externus, which I'll talk about shortly, but this muscle is the obturator internus because
it lies on the medial surface of the internal surface.
So you can see it originating here and it bends 90° around and then comes to and insert
on the femur at the greater trochanter.
So that's the obturator internus muscle.
You can see that 90° bend and its origin on the obturator membrane on the medial surface.
So you've got the piriformis, then you've got the gemellus superior, the obturator internus
and then the gemellus inferior underneath the obturator internus.
So just inferior to the gemellus inferior, you've got this quadrangular shaped muscle.
This is called the quadratus femoris muscle.
This again externally rotates, laterally rotates the femur.
All these muscles laterally rotate the femur, but these four muscles actually can extend
the femur at the hip joint as well as laterally rotate it, but the quadratus femoris only
laterally rotates.
So the gemellus superior and the obturator internus muscle are innervated by the nerve
to the obturator internus.
And then the quadratus femoris and the inferior gemellus are innervated by the nerve to the
quadratus femoris.
The piriformis is innervated by branches from S1 and S2.
So those are the muscles of the gluteal region.
So just remember they're split into deep and superficial layers.
So next, I'm going to talk about the muscles of the thigh region.
The thigh can be split into three compartments -- an anterior compartment, a posterior compartment
and a medial compartment, which is separated by intermuscular septa.
So the anterior compartment is only innervated by the femoral nerve.
The medial compartment is mainly innervated by the obturator nerve and the posterior compartment,
the hamstrings are innervated by the sciatic nerve or branches of the sciatic nerve.
So the anterior compartment consists of the quadriceps muscle, which consists itself of
four muscles as the name suggests -- the sartorius and then the terminal end of the iliopsoas
muscle.
Let's just take a look at the iliopsoas muscle.
The iliopsoas muscle makes up part of the posterior abdominal wall.
I'll just remove the muscles so we can take a look at them.
So you can see that it consists of two muscles.
We've got the psoas major and the iliacus.
So the iliacus muscle, you can see it sitting here in the iliac fossa and you can see the
psoas major originating on the vertebral bodies here and then it winds down to form this common
insertion point on the femur.
This muscle has two origins.
You've got the psoas major originating up here and you've got the iliacus muscle originating
in the iliac fossa.
These muscles are collectively known as the iliopsoas muscle.
So what this does is it flexes the femur at the hip joint.
So as you can see, the terminal ends of this muscle are part of the anterior compartment
of the thigh.
So the psoas major muscle is innervated by the anterior rami of L1, L2 and L3.
The iliacus muscle is innervated by the femoral nerve along with the other muscles of the
anterior compartment.
We'll just take a look at the rest of the muscles.
We'll start off with this muscle here.
This is the rectus femoris muscle.
The quadriceps muscle consists of four muscles as the name suggests.
We've got the rectus femoris and then you've got the three vastus muscles.
So you've got the vastus medialis, which are these teardrop-shaped muscle on the medial
side.
We've got the vastus lateralis, which is this muscle sitting laterally.
And you've got the vastus intermedius, which lies underneath this muscle here, the rectus
femoris muscle.
So these four muscles converge at this common insertion point onto the patella bone via
the quadriceps tendon.
And then the patella attaches to the tibial tuberosity via the patella ligament.
The rectus femoris muscle is interesting because it attaches to the pelvic bone, so it acts
also as a hip flexor whereas the vastus muscles originate on the femur so they only extend
the knee.
So if we just take a look at these muscles in isolation, you can see this muscle, the
rectus femoris originates on the anterior inferior iliac spine.
And there's also another head, which isn't shown here, which is reflected back inserting
superiorly to the acetabulum fossa.
So it originates on the pelvic bone, which allows it to act as a hip flexor.
So removing the rectus femoris, looking underneath, you can see this muscle here, the vastus intermedius.
This lies between the vastus lateralis and the vastus medialis.
So you can see these muscles have an origin on the femur and they insert onto the patella
tendon via this common quadriceps tendon.
So they act to extend the leg at the knee joint.
So the quadriceps are innervated by the femoral nerve.
Next, we've got this muscle, which is the last muscle of the anterior compartment.
It's called the sartorius.
It also originates on the pelvis, it winds around descending along the thigh obliquely
to insert on the medial surface of the proximal tibia.
So that's the sartorius muscle.
I've just isolated it again and you can see its origin here on the anterior superior iliac
spine.
It winds down like this, like a band onto the medial surface of the proximal tibia.
And this again is innervated by the femoral nerve because it's in the anterior compartment
of the thigh.
So because this muscle originates on the pelvis, it also acts as a hip flexor and it also flexes
the leg at the knee joint.
So unlike the quadriceps which extend, this flexes the leg at the knee joint and also
flexes the hip joint.