Hello anatomy colleagues this is Dr Alsup and in this video we will be discussing
the muscles of the medial compartment of the thigh. And as I assume you're
getting used to we will be discussing of course the major muscles with innervation
attachments and you can't forget the actions of these muscles. So as you might imagine the medial
compartment is located in the medial portion of the thigh and portions of it actually can be
seen in the anterior view as well so this is kind of showing a closer up view
with a deeper dissection but you can see a few of these muscles from this anterior view as well.
There are five major muscles: there are the three adductor muscles, adductor longus to me
is tied with gracilis one of the easiest to locate as it is large it's fan shaped muscle it's
more anteriorly placed so it's one of the more prominent ones that you can see particularly from
an anterior view. Locating adductor brevis takes a bit more dissection as it is deep to the adductor
longus for some of its portion as well so you can see it right here is the adductor brevis but it's
also deep to the pectineus muscle which has been removed here so if you're looking at a straight
anterior view as you can see see here without any deeper dissection it's really not visible.
The adductor magnus as you might suspect is the largest adductor muscle and it's actually composed
of two parts. There is the adductor part which is the larger part and really the bulk of the
adductor magnus is going to to be that part you can see a little of it here and a little of it
here but there's actually another portion that's often referred to as the hamstring part and that's
more closely associated both in terms of actions and innervation to the hamstring muscles in the
posterior thigh it's often hard to differentiate the two when you're looking at it in a dissection.
The adductor magnus as a whole is actually quite posterior medially placed which makes
sense that some of that larger bulk that comes with this muscle would kind of head back more
posteriorly and not further medially to kind of reduce the bulk in that region,
but oftentimes you can see a little bit of it from this anterior view.
Another muscle I find on the easier side to locate or to identify is the gracilis muscle
as it is relatively superficial and it's the most medial muscle in this compartment, so you
can see a bit of it right here, it will continue down all the way even actually to the tibia.
And it just looks like a long strap running along the medial border. The obturator externus is also
usually included with the medial compartment but as its actions don't totally align with this
compartment we are going to mention it here and move on so that is why it is not bolded.
The majority of the muscles in this compartment are innervated by the obturator nerve you can
see that here coming off of the lumbar plexus similar to the femoral nerve so both are branches
of the lumbar plexus and this is another notable compartment that is not being innervated by the
sciatic nerve except for that hamstring part of the adductor magnus which is innervated by
the sciatic nerve specifically the tibial part of the sciatic nerve, the tibial part or tibial nerve
is one of its two terminal branches. And this is actually the the same innervation that we will see
when we get to the rest of the hamstrings so that'll be our next learning objective.
But 4.5 of the other muscles 4.5 out of 5 muscles are innervated by the obturator
nerve so definitely the predominant supply to this compartment. The obturator nerve actually
splits into two parts around the adductor brevis so you can see the adductor brevis here
and you can see this little nerve traveling over that would be the anterior portion
and then the deeper or on the deep surface of the adductor brevis you
would see the posterior compartment and that's going to send branches.
All the muscles mentioned in this compartment have a proximal attachment
somewhere on the inferior portions of the coxal bones and then as you might
imagine they're going to cross the hip joint region thus being able to affect action there.
The adductor muscles so the longus brevis and magnus have some level of distal attachment on
the linea aspera of the posterior femur so this is an anterior view here and you can kind of
get an understanding that these are attaching on the posterior side of the femur, and you can see
on this just osteological portion the linea asper aspera is this rather
long line running down the posterior portion of the body or the shaft of the posterior femur.
And so the different adductor muscles will attach along the extent of the linea aspera.
Of note the gracilis muscle actually additionally crosses the knee joint so most of these don't make
make its way to the knee joint but the gracilis does and it has an attachment on the tibia.
But gracilis is a relatively weak muscle so only providing synergistic actions to the knee.
Lastly we can't forget actions! This is one is a pretty easy one too so the adductor
or medial compartment of the thigh will primarily adduct the hip joint. So adduction is key here
which is pulling the thigh medially towards or even past the the median plane so moving it in
this direction. I always conceptualize this compartment and think of getting on a horse
and you instinctively adduct your thighs or kind of try to pull them closer to the medium plane
in order to lock yourself on that horse to keep yourself from falling so think about that kind of
action that can occur there in fact individuals who competitively competitively ride horses often
have very prominent linea aspera and hypertrophy adductor muscles because of that repetitive action.
The hamstring part of the adductor magnus always has to be the odd one out and once you learn the
specifics of the posterior compartment of the thigh you can lump that that part in with that.
But this hamstring part of the adductor magnus will assist the hamstrings
in extension of the hip joint. Excellent thank you for all your time and attention here
and please do feel free to reach out with any questions. Have a great rest of your day