hello anatomy friends this is Dr. Alsup and in this video we are going to talk about the muscles
of the abdomen and we're going to start with talking about what bones there are
associated with the abdominal region and then we'll get into the muscles so
kind of a trick question right off the bat in terms of what bones are going to be associated
with the abdominal region well obviously if you're looking in the posterior region you do have some
of the vertebral column that is playing a role so a little bit of the thoracic into the lumbar
region will be protecting the posterior portions of the abdomen but generally when we think about
the abdomen we're thinking from a more anterior location and there are no bones anteriorly and
there's a lot of viscera when you're talking about within the abdominal cavity so what is protecting
those structures well it's muscles and the muscles are organized in such a fashion that they are
going to be running kind of in opposite directions similar to what we had with the intercostal
muscles but a bit more robust than what we have with the intercostal muscles so they're kind
of organized almost like plywood to really help protect this region without the additional support
of bone so we're going to start with the muscles of the anterolateral abdominal wall so kind of
on the sides here and generally we think of these as our oblique muscles there are two types of
oblique muscles there's the external oblique as its name would suggest it's more superficial you
can see that the direction of the fibers in this illustration here you have the internal
oblique muscles which are intermediate in terms of depth and then the deepest will be the transversus
abdominis so you can see fibers are going in different directions to provide that protection
now there are a few roles that these muscles can play if you think of like an oblique crunch that
will play a role in terms of being able to do that but really its most important function is
to help support and in certain situations compress the abdominal viscera it's playing
the role of protection it's playing almost like a bone role in terms of that so it's got to when it
contracts it's to really just keep everything kind of in the the right place so these are the muscles
that are going to be anterolateral and their tendons and we'll talk a little bit about this
are going to be very distinctive in the fact that these will be aponeuroses
and will will form this fairly prominent thing anteriorly which is the rectus sheath so
again an aponeurosis is just a name for a wide tendon and that's exactly what's going on here
those anterolateral abdominal wall muscles their tendons will move anteriorly they will
split to enclose the anterior rectus abdominis so you can see this here on the illustration
so well let's first look at this image here so the rectus sheath is very it's rather opaque
it looks white in terms of that often what will happen with tendons you can see
that when you reflect the rectus sheath you're looking at another muscle which is not where
the tendon comes from the tendon as you can see is coming from those anterolateral abdominal muscles
so very very prominent when looking at the anterior portion of the the wall and again
it will enclose the rectus abdominis and right in the midline those fibers from the tendons
will really coalesce they will become thicker and this region is referred to as the linea
alba and you can see a rather prominent one here it will extend all the way down towards the
the pubic symphysis region and this is really just a midline raphe going along the middle
here so if thinking midline and the abdominal wall you need to be thinking the linea alba
so what so we talked about that rectus sheath and when you open up the rectus sheath you have this
rather long muscle that is within the the rectus sheath region and this is the
rectus abdominis rectus just means straight and again one of the most prominent things
about the rectus abdominis is that it is long it extends all the way from the costal margin region
xiphoid process down to the pubic symphysis so it has quite a bit of an expanse to cover
it similar to the anterolateral abdominal muscles will play a role in terms of compression of that
abdominal viscera so again protecting those deeper structures it also when
contracting can play a role in terms of flexing the waist if you think of like a typical sit up
these muscles are are going to be activated and another prominent thing that you can
see in terms of the rectus abdominis are these tendinous tendinous intersections
that we you will find throughout typically there are three pairs sometimes there is a fourth and
if these muscles of the rectus abdominis muscles become hypertrophy ooh i'm having
a hard time saying that if they become hypertrophied that can create these tendinous
intersections are creating that kind of six-pack appearance or an eight pack in certain cases
all right excellent so tremendously important area but a rather simplistic area in terms of
the amount of muscles that are present so question here for review an incision to the
midline of the abdomen would most greatly affect which of these structures is it the external
oblique or internal oblique, the linea alba, the rectus abdominis, or the transversus abdominis
so pause the video and when you're ready let's discuss this well really if i'm
getting quite technical an incision to the midline could affect any of these structures
because but the answer i was going for so it would be most greatly would be the linea alba because
that is right there in the midline of the abdomen associated with the rectus sheath now if you have
a disruption of the linea alba or the rectus sheath that can certainly affect the muscles
that create the rectus sheath so those are the tendons of these anterolateral
muscles so that can affect the integrity of those muscles the rectus abdominis is just deep
within the rectus sheath it's not right down the midline it's generally right next to the midline
or linea alba region but it could be affected as well because that rectus sheath linea alba
region is affected too but really the answer I was going for here is that midline
structure of the abdomen and that is certainly the linea alba all right excellent thanks for
thinking through this with me if you have any questions regarding these muscles please don't
hesitate to ask and if not we're going to move into the upper limb thank you