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.