Okay, so I'm going to do a couple of tutorials on the muscles of the thigh.
So the muscles of the thigh are arranged into three compartments.
You've got an anterior compartment, medial, and posterior compartment and these are separated
by the intermuscular septum.
So the anterior compartment is known as the extensor compartment, the medial compartment
is known as the adductor compartment, and you've got the posterior compartment which
is the flexor compartment.
So these various compartments have different actions on the hip and knee joints.
And the different compartments are supplied by different nerves.
So the anterior compartment is supplied by the femoral nerve.
The medial compartment is supplied mainly by the obturator nerve, and the posterior
compartment of the thigh is supplied by the sciatic nerve.
So in this first part of the tutorial I'm going to talk about the anterior compartment
of the thigh.
So this is this group of muscles here anteriorly in the thigh, obviously and these muscles
are supplied by the femoral nerve.
And you've got five muscles in this compartment.
You've got the four large quadriceps femoris muscles, and then you've also got the sartorius
muscle.
As well as these muscles, you've also got the terminal ends of two muscles here.
So the iliacus and the psoas major, you can see them superiorly here, on the anterior
compartment, the terminal ends of these two muscles.
I'll show you these muscles now.
So we'll take a look at the iliopsoas muscles.
Now the iliopsoas muscles are the psoas major and the iliacus.
So collectively the iliacus and psoas are knows as the iliopsoas muscles.
So the iliacus muscle is this muscle here.
And it inserts onto the lesser trochanter of the femur together with the psoas major
muscle.
So this is the psoas major muscle here and they have this common insertion point on the
lesser trochanter of the femur.
So the iliopsoas and the iliacus muscle are collectively referred to as the iliopsoas
muscles.
So you can see here I've just highlighted the iliacus and psoas major muscles so you
can see the origin and the insertion a bit more clearly.
So you can see the psoas major muscle originating on the sides of the vertebral bodies of the
transverse processes and the intervertebral discs.
And it originates from the vertebral bodies from L-sorry, T12 down to L5.
And you can see its insertion on the lesser trochanter of the femur.
And also the iliacus muscle which sits in the iliac fossa, and then inserting on the
same place on the lesser trochanter.
So, what these muscles do is they flex the hip.
Flex the thigh at the hip joint.
Okay, so the next group of muscles in the anterior compartment are the quadriceps femoris
muscles.
So you've got four muscles in this group.
You've got the rectus femoris muscles, and you've got the three vastus muscles.
So you've got the vastus medialis, lateralis and intermedius which lies on top of the rectus
femoris muscle.
So, the rectus femoris muscle is interesting.
It originates on the pelvis.
So it has action both at the hip joint and at the knee joint whereas the vastus muscles
only act at the knee joint.
So the rectus femoris muscle is this muscle here which lies in the anterior compartment
and is the most superficial muscle.
So this muscle originates on the pelvis, on the anterior inferior iliac spine, and its
also got another head which is called the reflected head which isn't shown on this model
but it's reflected back and originates just superior to the acetabular fossa.
So there's two heads to the rectus femoris muscle; one originates on the anterior inferior
iliac spine, and the other is reflected back and it originates on the... just superior
to the acetabulum, and that's called the reflected head.
The head that originates on the anterior inferior iliac spine is known as the straight head.
So the rectus femoris along with the vastus muscles inserts by the quadriceps tendon onto
the patella bone.
And the patella bone inserts onto the tibia by the patellar ligament.
So a muscle is attached to the bone by tendons and bone is attached to bone by ligaments.
So the quadriceps tendon is this common insertion onto the patella bone.
And the patella then inserts onto the tibia by the patellar ligament so it's attached
to the tibia by the patellar ligament.
So because the rectus femoris originates on the pelvis, it flexes the thigh, the hip,
whereas the vastus muscles don't do that because they originate on the femur.
So let's take a look at the vastus muscles.
So I'll just get rid of the rectus femoris muscle.
And you can see this muscle here sitting laterally, this is the vastus lateralis.
And again, this originates from the femur and it inserts onto the patella by the quadriceps
femoris tendon.
Then medially you've got this teardrop-shaped muscle, which is known as the vastus medialis
because it sits medially.
And this again inserts by the quadriceps femoris tendon by the patella.
And just under the rectus femoris muscle, which I removed, you've got this muscle here,
the vastus intermedius.
So these three muscles all originate on the femur and they insert onto the patella by
the quadriceps femoris tendon and extend the leg at the knee joint.
So the final muscle we have is this muscle here called the sartorius.
This is a strap-like muscle which runs from the anterior superior iliac spine, all the
way down on the medial surface of the proximal tibia.
So this is the sartorius muscle and it acts to flex the thigh at the hip joint and also
to flex the thigh at the knee joint.
So let's take a look at it more isolated.
So you can see you've got the anterior superior iliac spine here where the sartorius muscle
originates and just below you've got the anterior inferior iliac spine where the rectus femoris
muscle originates.
And the sartorius winds around obliquely descending along the thigh to insert on the medial surface
of the proximal tibia.
So the insertion point here is just anterior to the insertion point of the gracilis and
the semitendinosus muscle.
So you can see you've got the hamstring muscle here and the gracilis, so they insert just
behind the insertion point of the sartorius muscle.
So that's the sartorius.
So, these were the muscles of the anterior compartment of the thigh.
You've got the iliopsoas muscles, you've got the quadriceps femoris muscles and you've
got the sartorius muscle.
And the muscles that originate on the pelvic bones have actions at the hip and knee and
the muscles that originate only on the femur only act on the knee joint.
So the rectus femoris muscles and the iliopsoas muscles act on the hip, and the quadriceps
femoris muscles act at the knee.
And these muscles are innervated by the femoral nerve.