Okay let's continue our discussion of the skeletal muscle and now we're finally getting
into the appendages and we're gonna start with the lower limb now we're going to focus quite a
bit of our efforts in terms of skeletal muscle in these appendages because this is really where the
majority of your muscles are particularly your your bigger muscles your more forceful powerful
contracting muscles specifically in the lower limb so we're gonna split this particular discussion in
terms of regions and we're going to start with the femoral or the thigh region so not only the
anterior portion but also the posterior portion then we'll continue later with the leg and the
foot region so let's start with the anterior compartment of the thigh and these are some of
your strongest muscles of the whole body right in this region particularly your quadriceps femoris
right here this is a complex of four muscles and we'll talk about this in a bit more detail but
there are other muscles in this region as well your iliopsoas which is a very powerful flexor
of the thigh and your sartorius which has the distinction of being your longest muscle in the
body all right so it's going all the way from up in terms of the pelvic girdle all the way to your
tibia so a very long muscle now the muscles of the anterior compartment of the thigh are going
to play a role in terms of flexion of the hips so think of moving your entire lower appendage
anteriorly and as well as extensors of the knee so when you think of standing up straight or if
you are getting up from sitting you are going to be extending your knees or straightening
straightening those out and most of these muscles are going to be innervated by your femoral nerve
so very large nerve from the lumbosacral plexus so let's actually look at some of these
so in this particular dissection we're looking anteriorly let's start with the sartorius and
you can see here is your ilium so remember putting hands on your hips we're feeling
the iliac crest so it's going to extend from there all the way kind of wrap around to your
tibia so a very long expanse in terms of what it does now the sartorius is more of what we refer
to as a synergist meaning that it's not a very powerful contractor it's going to assist other
muscles and actions and a lot of times you hear this muscle referred to as the tailor's muscle
if you think of sitting crisscross all the actions that occur to allow for you to sit
in this position the sartorius will play a small role in terms of that now let's focus
a bit more on the quadriceps femoris and this is this main complex of the anterior compartment so
all these muscles right here like I said and as the name would suggest it's going to be made up
of four separately named muscles that kind of come together now remember when we were talking about
the osteology portion we had that important sesamoid bone right in there the patella is
actually going to form within the tendon of your quadriceps femoris so let's look at this
in a bit more detail these different components you're gonna have your vastus medialis and as its
name would indicate this is the more medial one right in the middle and superficial is the rectus
femoris and then the largest component of your quadriceps femoris is the vastus lateralis and
obviously as the name would indicate its lateral this is the muscle that a lot of physical therapy
when you're conditioning the muscles in this region a lot of those exercises focus on the
vastus lateralis so it can really help protect your knee joint in this region now if you were
to reflect your rectus femoris then you can see that fourth component of the quadriceps
and that's your vastus intermedius so in between the medialis and the lateralis and deep to the
rectus femoris so think about we discussed it previously but what are these muscles do and
they contract that's right they're going to extend your knee joints so straighten out the knee joint
one other muscle that that I skipped but we want to come back to it is the iliopsoas the
iliopsoas is actually made up of the combination of two muscles you have your psoas major and your
iliacus muscle and those two muscle bellies they have a common tendon and we refer to that as the
iliopsoas and you can't really see it very well in this visual it's actually quite difficult to
see unless you reflect a lot of the muscles right here so it'd be deep to this but here's
your psoas major and your iliacus is right in this region and this is a very powerful muscle this is
the main flexor of the hip so although you can't really see in this particular dissection because
it's deep it's a very important muscle now let's move to the medial compartment of the thigh so
you can also see these typically in an anterior view as well but they're going to be separated
they're going to have their own fascial compartment and they're going to be more medially placed and the
main muscles here are your adductors and you're going to have three adductor muscles you'll have
a longus adductor longus adductor brevis and the big one and the more powerful one adductor magnus
additionally the most medial muscle of the medial compartment is your gracilis muscle this is a not
a very powerful muscle it will play a synergistic role in terms of adduction now I have right here
a picture of the femur obviously and importantly this is going to be a posterior view and you see
this line right on the shaft of the femur and the posterior view this is your linea aspera this is
going to be the distal attachment for most of these muscles of the medial compartment so if
you think about contracting those what are they going to do contract those adductor muscles well
obviously they're going to aduct the thigh or put them back more into anatomical position
so whereas the muscles of the anterior compartment are going to be innervated by the femoral nerve
the medial compartment is going to be innervated by the other large nerve of the lumbar plexus
the obturator nerve so let's actually look at some of these muscles so you can see in
this visual this is an anteromedial view so here are those anterior compartment muscles or
the quadriceps femoris and you can see where this is obviously medial here is your adductor
longus your abductor brevis would be deep to the longus and then your gracilis is your most medial
muscle right here one muscle that you can't see in this view is your adductor magnus and
it is easier to see this muscle from a posterior view of the thigh and you can see it right here
so very closely associated with those hamstring muscles in the posterior thigh and actually the
adductor magnus has a component that acts in the same way as the hamstring muscles now there are
a few clinical considerations that I want you to think about in terms of a medial compartment one
and this is a common theme for these muscles that are more synergistic what we refer to as
gracilis transplantation so if you were to remove components of the gracilis muscle it's not going
to play that big a role in terms of the actions of the thigh so you can take portions of the muscle
fibers there and transplant them to other areas particularly the external anal sphincter you can
move muscle fibers from there from the gracilis to this region if you have extreme damage there
and it won't affect the muscle or the actions of the medial compartment of the thigh additionally
when you hear the term groin pull it's typically talking about some type of damage to the proximal
attachment attachments of the adductors so let's think where would these proximally attach
if you're thinking about a groin pull what's very closely associated osteologically that's
right the pubis bone all right so your proximal attachments going to be the pubis bone if you
have a tear there in terms of the tendons if you have inflammation this would be what we refer to
as a groin pull all right now let's move so we were talking anteromedial now we're
gonna move posteriorly and we'll talk about some of the most powerful muscles you had your
quadriceps in the anterior and you'll have your gluteal muscles in the posterior so let's start
with the big one as its name would indicate your gluteus maximus and this is really what's forming
the bulk of your gluteal region and you can see right here it's the most superficial of your
gluteal muscles and the largest the fibers in this region are very coarse very thick it's very hard
to dissect this region because the muscle fibers kind of intertwine with the deeper medius and
minimus now one thing I want you to note in this dissection its main distal attachment
is your IT band or your iliotibial tract so that makes sense in terms of the main action of this
muscle is going to be extension of the thigh so if you think about climbing stairs your gluteus
maximus are really playing a big role in terms of that extension so let's this is a superficial
dissection here if we were to reflect the gluteus maximus then you're gonna see the deeper gluteus
medius and the gluteus minimus and as their names would indicate this is going to be the second
largest and the third largest of the gluteal region now these muscles unlike the gluteus
maximus they have a different insertion site which is going to be the greater trochanter of
the femur so they have a separate attachment site so obviously they're going to have a different
action and that's going to be abduction or moving the the hip joint or your thighs away from the
midline as well as playing a role in terms of medial rotation of the thigh now these two muscles are
going to have a different innervation than the gluteus maximus and we didn't talk about that
before gluteus maximus is going to be innervated by your inferior gluteal nerve whereas the medius
and minimus are going to be innervated by the superior gluteal nerve so let's actually look
at these muscles here so your gluteus maximus and this image has been reflected and you can see how
large and how thick these fibers are they're just deep - that is your gluteus medius you
can see that piriformis that we discussed before which is exiting the greater sciatic notch and in
order to really see the gluteus minimus you also have to reflect the medius and you can see this is
going to be right on the bone for the gluteus medius so one other thing I want to make sure
you understand so we talked about how the gluteus medius and minimus are innervated by the in excuse
me the superior gluteal nerve and they play a role in terms of abduction and medial rotation of the
hip but really the main role of the medius and minimus is to help your hips stay in line okay
the sides of your hips from kind of falling when it contracts or when your locomoting or walking so
if you have injury to your superior gluteal nerve so say you have a injury to your right superior
gluteal nerve that can have implications in terms of how you walk so in a typical walk you're going
to lift your left foot and the right gluteus medius and minimus are going to contract and
allow for your pelvic girdle to stay in line but say your superior gluteal nerve
on the right side has been injured when you lift your left foot this is not going to be
able to contract this right gluteus medius is not going to be able to contract so you'll actually
kind of tip your pelvic girdle and allow for you not to be able to pick up your foot as well as
you typically would so locomotion will be very very much affected in some type of injury here
and this is referred to as your Trendelenburg sign or a positive Trendelenburg sign alright
let's go back to the piriformis I told you that we'd get back to it and here we are so in this
particular visual the maximus and the medius have been cut you can see your gluteus minimus here and
then this pear-shaped piriformis recall that it attached from the sacrum and it's got to go
all the way to the greater trochanter in order to play a role in terms of lateral rotation now let
me erase this right here so you can see a clean view of the piriformis there is a very important
nerve that's also exiting through the greater sciatic notch inferior to the piriformis and it
is the main nerve of your lower limb your sciatic nerve and we've all heard of that sciatic nerve
is the largest nerve of the body and it's going to innervate all muscles of the lower limb except for
those in the anterior and medial compartments of the thigh so everything in the posterior thigh as
well as the lower limb or the leg in the foot so let's talk about that posterior compartment of the
thigh so this is the last area that we're going to talk about in this particular presentation
and we refer to these muscles of the posterior compartment of the thigh as your hamstrings and
we've all heard of that before and these are very rope like muscles so they're very strong
very powerful particularly your biceps femoris muscle and that's going to be the more lateral
muscle you also have your semitendinosus and your semimembranosus and we'll actually look at those
in a moment importantly these muscles have a proximal attachment of the ischial tuberosity
so remember that ischial tuberosity and the posterior portion of the pelvic girdle is very
built up because it has these strong muscles attaching here these muscles are going to be
innervated by that sciatic nerve that we just discussed and specifically the tibial portion
of the sciatic nerve and you'll get into this in a bit more detail in the neuro portion but
I want to introduce the concept here because it's important sciatic nerve largest nerve of your of
your body it's really made up of two components the tibial and your common fibular nerve so even
though at this point in the posterior thigh these two portions are combined they're wrapped up in a
connective tissue together it's really only these fibers of the tibial portion that are
innervating the hamstrings so lastly think about your hamstring muscles think about what happens
when you contract them so you're flexing the leg so if you think about flexing the
knee these are the main flexors of the knee and they also will play a role in terms of extension
of the thigh or of your hip joint now remember what's the other main extender of the thigh is
the gluteus maximus so how are these different in terms of their roles well the hamstrings
are going to be tonically contracted when you're standing upright when you're just standing during
a lecture working etc if you're not actively moving from flexion of the thigh to extension
that's more of the gluteus maximus the hamstrings are more tonically contracted so let's look at
these you have your like we discussed before your biceps femoris is kind of the powerhouse in terms
of your hamstrings and this is going to be the lateral of the hamstring muscles and then you're
going to have the kind of paired on the other side semimembranosus and semitendinosus and how
you can tell these apart really come into their name so the semitendinosus and you can see right
here this is going to have a much longer tendon it's going to extend to the tibia like all the
hamstring muscles do so it has a very dominant tendon where and this is also going to be more
superficial so superficial to the membranosus which is going to be deep and really if you're
looking at a posterior view of a thigh you're not going to see very or a dominant rope like tendon
for the semimembranosus like you do with the semitendinosus but really in terms of that flexion
of the knee this biceps femoris is really the the powerhouse there so we see muscles here that are
actually extending past the knee joint so playing a role in terms of the actions of the knee joints
we're going to continue our discussion in the next presentation for those muscles that are
actually within the leg that are going to affect both the ankle as well as the digits of the foot