Muscles of the Thigh and Gluteal Region

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Transcription

Part 1

Okay, so this is a tutorial on the muscles of the gluteal region and the muscles of the thigh.  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.

The gluteal region is this region here between the iliac crest and the gluteal fold, so the fold of the buttock.  It’s helpful to think of the gluteal region in terms of deep and superficial muscles.  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.

 

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.

 

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.  That’s the tensor fasciae latae muscle. You can see the spelling here.

 

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.

 

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.  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.

 

You’ve got a ligament which runs from the ischial spine to the sacrum and that’s called the sacrospinous ligament.  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.

 

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.  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.  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.

 

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.

 

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.

 

The obturator internus muscle actually sits – I’ll just get rid of these muscles and ligament.  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.  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.  You can see it originating here and it bends 90° around and then comes to and insert on the femur at the greater trochanter.

 

That’s the obturator internus muscle. You can see that 90° bend and its origin on the obturator membrane on the medial surface.

 

You’ve got the piriformis, then you’ve got the gemellus superior, the obturator internus and then the gemellus inferior underneath the obturator internus.

 

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.

 

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.

 

Those are the muscles of the gluteal region.  Just remember they’re split into deep and superficial layers.

 

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.

 

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.

 

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.  You can see that it consists of two muscles. We’ve got the psoas major and the iliacus.  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.  What this does is it flexes the femur at the hip joint.  As you can see, the terminal ends of this muscle are part of the anterior compartment of the thigh.

 

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.  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.

 

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.

 

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.  It originates on the pelvic bone, which allows it to act as a hip flexor.

 

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.  You can see these muscles have an origin on the femur and they insert onto the patella tendon via this common quadriceps tendon.  They act to extend the leg at the knee joint.  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.  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.

 

Because this muscle originates on the pelvis, it also acts as a hip flexor and it also flexes the leg at the knee joint.  Unlike the quadriceps which extend, this flexes the leg at the knee joint and also flexes the hip joint.

 

Part 2

Now, we’re going to move on to the medial compartment of the leg. The medial compartment consists of six different muscles. We’ll take a look at those now.

 

I’ll just get rid of the sartorius and we can look at the medial compartment muscles. These muscles originate in this area of the pelvis. The body of the pubis, the ischiopubic ramus, this sort of area is where the muscles of the medial compartment originate. These muscles are mainly innervated by the obturator nerve.

 

There are two muscles that are innervated by separate nerves. You’ve got the pectineus muscle, which is this muscle here. That’s innervated by the femoral nerve and you’ve got the hamstring parts of the adductor longus muscle, which is innervated by the sciatic nerve (the tibial branch of the sciatic nerve). Apart from that, they’re all innervated by the obturator nerve.

 

These muscles, this group of muscles mainly adduct the femur at the hip joint.  I’ll the first muscle I’ll talk about is this muscle, which is most medial and it runs vertically down the medial aspect of the thigh.  This muscle is called the gracilis muscle. You can see its course down the inside of the leg from the body of the pubis inserting onto the medial surface of the proximal tibia.  It inserts just behind the insertion point of the sartorius. This muscle adducts the thigh and it flexes the knee.

 

Next, we’ve got the pectineus muscle. You can see this muscle here. It’s rectangular in shape. It’s innervated by the femoral nerve rather than the obturator nerve. I’ve just isolated it here and you can see it originating here on the pectineal line and inserting onto the femur.  What this muscle does, it adducts and flexes the thigh at the hip joint. That’s the pectineus muscle.

 

And then we’ve got a group of muscles called the adductor muscles. You’ve got the adductor longus, the adductor brevis and the adductor magnus. This is the most superficial of the adductor muscles and this is called the adductor longus. This muscle adducts and medially rotates the thigh. The medial border of this muscle forms the medial border of the femoral triangle.

 

I’ve just brought back the sartorius muscle just to explain the femoral triangle. The femoral triangle is this area on the upper thigh. The superior border is the inguinal ligament which runs from the anterior superior iliac spine down to the pubic tubercle. That’s the superior border.

 

Then you’ve got the lateral border formed by the medial border of the sartorius muscle, this margin here. And then like I’ve just mentioned, you’ve got the medial border of the adductor longus muscle, which forms the medial border of the femoral triangle.  The femoral triangle is this region here.

 

The adductor longus and the pectineus muscle adjacent to it form the medial part of the floor of the femoral triangle. And then you’ve got the lateral part formed by the terminal ends of the iliopsoas muscle.  That’s just a quick bit about the femoral triangle.

 

We’ll just take a look at the adductor longus muscle. You can see its origin on the femur and the middle third of the femur.

 

I’m just going to dissect away some of these muscles. You’ve got the pectineus here. You’ve got the adductor longus, which I’ve just shown you. I’m just going to remove that muscle, so you can see what’s beneath.

 

You’ve got this smaller muscle, which inserts on the femur a little higher up in the upper third of the femur. This is called the adductor brevis. Remember ‘brevis’ means short in Latin, so it’s a shorter muscle. The adductor longus inserts further down here.  This muscle, the adductor brevis muscle lies behind the pectineus and the adductor longus muscle. This muscle adducts the thigh.

 

Most deep, we’ve got this huge muscle underneath. I’ll just get rid of the adductor brevis and we can see this big muscle here. This is called the adductor magnus muscle. ‘Magnus’ means big or great in Latin, so it’s the biggest adductor muscle and it’s got two parts.

 

It’s got a hamstring part, which is this part here, which runs up vertically. You’ve got the adductor part, which is this part here. I’ve just isolated it to give you a good view.  You’ve got the hamstring part, which runs vertically up and you’ve got the adductor part, which is this part here.

 

The hamstring part of the adductor magnus is innervated by the tibial branch of the femoral nerve rather than the obturator nerve.  This part, the adductor part is actually innervated by the obturator nerve and they’ve got two different origins.

 

The hamstring part essentially descends vertically and it originates on the ischial tuberosity, whereas the adductor part originates on the ischiopubic ramus.  This muscle adducts and medially rotates the thigh.

 

Finally, we’ve got the obturator externus muscle. You can see this muscle here. It sits on the lateral surface of the obturator membrane and it winds around behind the hip joint to insert into an oval depression in the trochanteric fossa.

 

I just isolated it again here. You can see it sitting on the obturator membrane over the obturator foramen and it winds around behind the hip joint and it inserts into this little depression here, the trochanteric fossa. This muscle externally rotates the thigh.

 

If you remember the obturator internus muscle, it sits on the medial surface of the obturator membrane.  You can see that there and its 90° bend around. You can see the obturator externus and internus.

 

Again, the obturator externus is innervated by the obturator nerve.  Just bringing back the muscles of the medial compartment, you’ve got two muscles, which aren’t innervated by the obturator nerve in the medial compartment. You’ve got the pectineus muscle, which is this rectangular muscle here innervated by the femoral nerve and you’ve got the hamstring part of the adductor longus muscle, which is innervated by the tibial branch of the sciatic nerve. But apart from that, the rest are innervated by the obturator nerve.

 

Okay!  The final compartment of the thigh is the posterior compartment. The posterior compartment is very simple because then you’ve got three muscles there. I’ll just remove the gluteus maximum to get a good look at this compartment.

 

The muscles in this compartment are innervated by branches of the sciatic nerve. These muscles, apart from the short head of the biceps femoris muscle, these originate, all originate on the ischial tuberosity. They run down to insert on the tibia. They extend the hip joint and flex at the knee joint.

 

You’ve got three muscles. You’ve got this muscle here, which sits laterally. This is the biceps femoris muscle. It has two heads. You’ve got a long head, which originates on the ischial tuberosity and you’ve got a short head, which originates on the femur. It inserts onto the head of the fibula.

 

And then medially, you’ve got the semimembranosus muscle and the semitendinosus muscle.  A way of remembering it is semimembranosus has an m in it, so m for media. Semimembranosus and semitendinosus both have a semi- in it, so they both go together. They’re both medial. Because semimembranosus is medial, so semitendinosus is medial. And then because semitendinosus has a t in it, so semitendinosus sits on ‘top’.

 

Biceps femoris laterally and then you’ve got semimembranosus and semitendinosus medially with semitendinosus sitting on the top.

 

I’ve just isolated these muscles and you can see the origin of these muscles on the ischial tuberosity. And then you can see the short head of the biceps femoris muscle originating on the femur.  The long head and the short head converge into this common tendon and then inserts onto the head of the fibula.

 

The biceps femoris muscle extends at the hip joint and flexes at the knee joint. The semitendinosus is the one that sits on the top and its medial to the biceps femoris muscle and it runs down and inserts on the medial surface of the proximal tibia.  It inserts just behind the gracilis muscle.

 

If I just bring the other muscles back in, you can see the gracilis here running down and it inserts just behind the sartorius muscle, but just in front of the point where the semitendinosus muscle inserts.

 

The semitendinosus muscle, again, it flexes the knee and it extends at the hip.  The semimembranosus muscle has the same action, extending at the hip and flexing at the knee joint. It works together with the semitendinosus muscle. Let’s just have a look at the insertion point. It actually inserts behind on the medial condyle of the femur and it also inserts posteriorly on the medial condyle of the tibia. And also, some of the fibers from the tendon blend with the fascia which covers the knee joint.

 

All these muscles of the posterior compartment or the three muscles of the posterior compartment are innervated by the sciatic nerve, so the main function of these muscles is to extend at the hip and flex at the knee.

 

That’s the muscles of the gluteal region and of the thigh. It’s probably quite long, but if you want to learn a bit more in detail about the various muscle actions and the points of origin and insertion, then take a look at my individual tutorials where I cover it in a bit more detail. Sorry if this was a bit more rushed, but feel free to rewind, re-watch, whatever and take a look at my other tutorials.