So in this second part of the tutorial, I'm going to talk about the medial compartment
of the thigh.
There are six muscles in this medial compartment.
These muscles are mainly innervated by the obturator nerve.
These muscles act mainly to adduct the femur, the thigh at the hip joint -- ad-duct, adduct.
So I'm not going to talk in too much detail about the origin and insertion of these muscles
because it takes quite a bit of time, so I just want you to get an idea of what these
muscle are and their actions.
So these muscles mainly originate on the body of the pubis and the ischiopubic ramus of
the pelvic bone, so this area on the pelvis and they insert at various points on the femur
and also in the case of the gracilis, on the tibia.
So this view here just shows the medial compartment muscles of the thigh.
I'll be flicking between the two models.
The first muscle we'll look at the gracilis muscle.
This muscle runs vertically down from the medial aspect of the pelvis on the body of
the pubis down to insert on the medial surface of the proximal tibia.
So I've just isolated it here and you can see its path.
So it runs vertically down the inside of the thigh, originating as you can see on the body
of the pubis and inserting on the medial surface of the proximal tibia.
So it inserts between the insertion points of the sartorius muscle, which inserts anteriorly.
Posteriorly, you have the insertion point of the semitendinosus muscle, which is a hamstring
muscle in the posterior compartment.
So you can see this muscle here.
This muscle, this is the semitendinosus muscle and you can see the tendon inserts just behind
the insertion point of the gracilis muscle.
And just anteriorly, you've got the sartorius muscle, which is a muscle of the anterior
compartment that descends obliquely along the thigh.
So the insertion point of the gracilis is sandwiched between these two on the medial
surface of the proximal tibia.
So this muscle is innervated by the obturator nerve and it acts to adduct the thigh and
it also flexes the leg at the knee joint.
So next, we've got the pectineus muscle, which is this muscle here.
So this muscle is a rectangular muscle and it's innervated by the femoral nerve.
So there are two muscles which are innervated by different nerves.
You've got the pectineus, which is innervated by the femoral nerve and you've got the hamstring
part of the adductor magnus muscle, which is innervated by the sciatic nerve.
So the pectineus muscle is innervated by the femoral nerve and it acts to adduct the thigh
at the hip joint and it also flexes at the hip joint.
You can see its origin up here.
This is the pectineal line.
It inserts here on the femur.
So this muscle actually forms part of the medial floor of the femoral triangle.
I'll do a tutorial on the femoral triangle, but this muscle forms part of the floor of
the femoral triangle.
So just to briefly tell you, the femoral triangle is this triangle bound superiorly by the inguinal
ligament.
You've got this medial border of the sartorius forming the lateral border of the triangle
and the medial border of this muscle, the adductor longus forming the medial border
of the triangle.
So it's this area here.
You can see the pectineus forming the floor of this triangle, the femoral triangle.
So next, we've got the adductor muscles.
You've got adductor longus, the adductor brevis and the adductor magnus.
The one you can see here is the adductor longus.
The adductor brevis and magnus sit deep to this.
So the adductor longus forms the most medial muscle of the floor of the femoral triangle
and its medial border forms the medial border of the femoral triangle.
So this is the adductor longus muscle.
You can see its origin here on the pubis and it inserts on the middle third of the shaft
of the femur.
So what this muscle does is it adducts the femur and it also can medially rotate.
And again, it's innervated by the obturator nerve.
I'll just get rid of some of these muscles of the anterior compartment, so we can just
get a clearer look at these medial muscles.
So you've got the pectineus, you've got the adductor longus muscle.
And underneath the adductor longus and pectineus, you can see the adductor brevis muscle.
So again, this muscle has its origin on the pubis and it inserts a little bit higher up
on the femur, the upper third of the femur.
What this muscle does is it adducts the thigh at the hip joint and again, it's innervated
by the obturator nerve.
So I'll just remove the adductor brevis and we can see this big muscle lying underneath
this.
This is the final adductor muscle.
This is the adductor magnus.
'Magnus' means great in Latin, so it's the big adductor muscle.
It's got two muscle bellies.
So you've got the adductor part and you've got the hamstring part, this little bit down
here.
So this lateral part of the muscle is the adductor part and the medial part is this
hamstring part.
It's this hamstring part of the adductor magnus that's innervated by the sciatic nerve, the
tibial branch of the sciatic nerve.
So in the medial compartment, everything is innervated by the obturator nerve apart from
this hamstring part of the adductor magnus and the pectineus muscle, which is innervated
by the femoral nerve.
So just taking a quick look at the origin of this muscle, you can see it's got quite
a broad origin.
It's got two origins for the hamstring part and the adductor part.
So the hamstring part originates on the ischial tuberosity and the adductor part originates
on the ischiopubic ramus.
You can see where this muscle inserts.
The hamstring part inserts on something known as the adductor tubercle on the medial condyle
of the femur, the distal femur.
You can see that there.
the adductor part inserts on the posterior surface of the femur.
This muscle adducts and medially rotates.
So there, it's just important to know about these two different parts.
And then you've got this little circular opening in the muscle.
This is known as the adductor hiatus.
This allows the femoral artery and veins to pass through.
If I just bring those in, you'll be able to see how they pass through this hiatus in the
adductor magnus muscle to run into the popliteal fossa.
The final muscle is the obturator externus muscle.
We'll just show you that.
If you remember from the tutorial on the gluteal region, you've got the obturator internus
which originates on the medial surface of the obturator membrane.
So the obturator externus is this muscle which originates on the lateral or external surface
of the obturator membrane.
So unlike all the muscles of the medial compartment, this one actually laterally rotates the femur.
It doesn't adduct.
So if we just take a look at this muscle, this is the obturator foramen and it's covered
by an obturator membrane.
You've got the obturator externus sitting on top of it.
It's this fan-shaped muscle and you can see how it extends behind the hip joint and it
inserts into this little -- you can see this little depression, this oval depression, in
this trochanteric fossa.
This is where it inserts and it laterally rotates the femur.
So you've got the obturator internus sitting on the medial side.
This is the obturator externus sitting on the medial compartment.
And again, it's innervated by the obturator nerve.
So those are the six muscles of the medial compartment of the thigh.
You've got the gracilis most medially.
You've got the pectineus, which is one that's innervated by the femoral rather than the
obturator nerve.
You've got the three adductor muscles with the adductor longus the most superficial,
the adductor brevis behind that and the big adductor magnus with its two heads, one of
which is innervated by the sciatic nerve (the hamstring part).
And then you've got the obturator externus muscle.
So those are the six muscles of the medial compartment of the thigh.