hello anatomy friends and welcome to station 25 where we are going to look at abdominal
wall muscles and recall how important and how functionally important these anterior lateral
abdominal wall muscles are because we don't have any bony structures associated with the anterior
portion like we did say with the sternum and the ribs when we're talking about the thorax
it is all about these muscles that are playing a role in terms of protection and compression of
the viscera if needed so when we're talking about the anterior lateral abdominal walls
a lot of times these are associated with the oblique muscles and these will go from and this
is looking at a section right here so we're kind of looking at a section of the anterior lateral
abdominal wall you can see the external oblique is going to be the most superficial with the internal
intermediate and then you have a very thin layer right here which is your transversus abdominis
and so these are the three layers of the anterolateral abdominal wall this is not an
image i would use in a practical i just wanted to kind of give you an idea of how thin these muscles
are but the fact that their fibers are running in different directions really kind of like
plywood allows for a lot of protection and a lot of flexibility in this area so similar to what we
had with the external intercostals these external oblique muscle fibers are going to be moving kind
of inferior medially whereas the internal obliques are going to be running perpendicular to that
and then the deepest transversus abdominus muscles the fibers are more transverse
even though they are some of them can look kind of similar to the internal oblique fibers as well
so if we're looking at a an anterior view where the subcutaneous tissue has been mostly removed
and we're looking at the muscles and sheath in this region you can see the external oblique in
this particular dissection because we have not gone deeper to that so the internal
oblique as well as the transversus abdominis have been
have been occluded from view because we can we're only looking superficially
and you can see this fairly prominent structure right here in the middle of the abdominal wall
and this is the rectus sheath this whole area right here is part of the rectus sheath and the
the rectus sheath is formed by the the tendons of those anterior lateral abdominal muscles so
the external oblique the internal oblique and that abdominus so those fibers of the tendons are going
to kind of intermingle to create this very robust rectus sheath and where they all kind of meet
and sometimes even decade or cross over are going to be is going to be the linear elbow
which kind of runs right down the midline so closely associated with the umbilicus
and it is going to appear a bit more opaquely white than the surrounding tendons
now if you open up that rectus sheath so if you reflect it you will see the straight
rectus abdominis and that would be the same thing here if you were to open up this rectus sheath
and the rectus abdominis rectus means straight so it's very straight in terms of muscle fiber
direction as opposed to the oblique muscles or the transversus abdominis on the side here
and it's going to be completely surrounded by the rectus sheath so you'll have a
posterior rectus sheath behind the rectus abdominis for almost the majority of its run
actually the rectus sheath kind of stops in the posterior inferior portion but one thing you can
really notice here in this rectus abdominis are these tendinous intersections that can be located
kind of throughout the muscle usually you have three sometimes you can have four and if you have
a hypertrophy of this muscle or you're contracting these muscles sometimes it can kind of bulge out
because these tendonous intersections will not so that's what kind of gives that
that six-pack appearance in certain very lean individuals with robust rectus abdominis muscles
okay so those are the muscles of the anterior lateral abdominal wall
in addition to the rectus sheath or the tendons of those anterior lateral muscles
work your way through this material if there's any particular areas that you're still
confused about you know it's always a good idea to reach out to me with any of those questions
thank you for your time here and i will see you at the next station