hello anatomy friends this is dr alsup and in
this supplementary dissection video we will be discussing some of the muscles particularly
associated with the abdominal wall certain structures associated with the inguinal
canal and anything in that surrounding area the inguinal canal is a traditionally
difficult area in dissection so we will take our time in this region to discuss some
of those basics that you need to know but let's start with the abdominal wall
first specifically the most superficial of the anterolateral abdominal wall
muscles which are the external obliques the muscle fibers of the external obliques run
in a similar direction as those of the external intercostal muscles between the ribs i always
think of kind of putting your hands in your front pockets in terms of the directionality
of the muscle fibers for the external oblique and if you're looking at a superficial dissection
you are looking at the external oblique you would have to reflect the external oblique to
see the deeper internal oblique and transversus abdominis and as we aren't asking you to identify
those you should be in pretty good shape there in terms of being able to identify this muscle i also
really like this image as it shows how the tendons of the oblique muscles really form
the rectus sheath which is this whole area right here on this particular
individual the rectus sheath is quite robust and um they're essentially continuous because
it is the tendons or the flattened tendons called the aponeurosis of the oblique muscles and
transversus abdominis that form the rectus sheath the sheath is pretty hard to miss it is the
dominant white and kind of variably opaque structure in the anterior portion of the
abdominal wall you can see see through it a little bit in terms of seeing some of the muscle
fibers but for the most part it's fairly opaque and running down the midline you have umbilicus
here so you know that you're in the midline is going to be the linea alba which means
white line and it's notably more opaque than the rest of the rectus sheath and
it's the medial most attachment point of those three anterolateral
abdominal muscles on both sides now let's see what we can see when we reflect a
portion of the rectus sheath which has been done here in fact in order to review the rectus
abdominis muscle you have to reflect the anterior portion of the rectus sheath which is
what's happened in this image on the left side the anterior rectus sheath has been left in place
on the right side so you can really only see the left rectus abdominis you can see how long the
rectus abdominis is it extends from the xiphoid process up here all the way down towards the
pubic symphysis so very long muscle and you can see the tendonous intersections that are going
to be interspersed throughout the muscle here on this particular individual there are three
on this side which is the most typical pattern now i put this second image over
here with the rectus abdominis reflected inferiorly in order to point out that
there is a posterior portion of the rectus sheath which you can see right in this region remember
that the rectus sheath is going to envelop the rectus abdominis but it's not complete it
actually ends about three-fourths of the way down and what you're left with in this inferior
most portion is just transversalis fascia which typically appears a little more transparent
than the posterior rectus sheath and this line of demarcation is called the arcuate line all right
let's move to the inguinal canal region and as i mentioned at the beginning this is a traditionally
complex region and there are a lot of structures that we're not going to have you identify
we're really only picking up on the structures that are on the easier side to identify the
more prominent structures now the inguinal canal extends from the deep inguinal ring which
as the name would suggest is deep and not visible from these more superficial dissections and the
superficial inguinal ring which has been opened on this dissection it would be right about
here but it is visible on this dissection so right here kind of where you have that opening
is going to be the superficial inguinal ring this is the exit or medial aperture of the
inguinal canal and is formed by the external oblique aponeurosis and you can typically see
structures exiting the canal and you can see that in both of these images we will start with
this one where you can see the round ligament of the uterus exiting the where the superficial
ring would be located and the round ligament is sometimes difficult to identify as it presents
as a tubular collection of adipose tissue which may be difficult to differentiate
from some of the surrounding adipose tissue but one thing that you can see a little bit of
here is that there and i drew already kind of a line through it is going to be a nerve called the
ilioinguinal nerve which will run superficial to the uh the round ligament sometimes that helps
with identification sometimes not so much as a rather small nerve but when you when you do
see a collection of fat or adipose tissue with a nerve running right on top of it you're
likely looking at that round ligament the round ligament of the uterus connects the uterus to the
labia majus although in some individuals it does not extend all the way to the labium majus into
adulthood and it's a remnant of the gubernaculum on this individual you can see the spermatic cord
exiting the superficial inguinal ring with that ilio inguinal superficial to it and you can see
on this side the spermatic cord has been dissected to show you the different components of the cord
and we will discuss both the round ligament of the uterus and the spermatic cord in more
detail in the reproductive anatomy session now one last thing i want to discuss here is the
inguinal ligament and you can't see it well here as recall that the inguinal ligament is the
floor of the inguinal canal and we can still see these more superficial structures of the
inguinal canal so it's occluding the view of the inguinal ligament but we can conceptualize
where it would be located as it extends from the anterior superior iliac spine to about the
level of the pubic tubercle around this region and um that is going to um to give you an
indication that that inguinal ligament is longer than the inguinal canal as it doesn't actually
begin the inguinal canal doesn't actually begin until the deep inguinal ring which is a
little bit more right around this region so that inguinal ligament is going to be made up
of external oblique aponeurosis and so it's going to be very similar in terms of composition
is what we see right around this region okay moving to the deep surface of the anterior
abdominal wall here and you can see peritoneal cavity over here you can see some of them
the omenta right here a little bit of viscera this all looks a bit a little
bit overwhelming i get that but there's a lot going on but let's
take these things one at a time so here um this individual is actually holding
the anterior abdominal wall that's been reflected and i can see kind of right off the bat one
of the most prominent things is i see the inferior epigastric vessels so you can see the two
paired veins and then the artery right in between and much of the peritoneum has been removed here
so this is less the lateral umbilical fold than just the vasculature now just lateral to this you
can see right around this region a collection or what looks like a tubular collection of adipose
tissue is entering into this region here all right and that's exactly what is happening this is
that round ligament of the uterus entering into the deep inguinal ring and so that area where you
have the invagination of the transversal fascia is the deep inguinal ring the entrance or
internal aperture of the inguinal canal now the round ligament tends to be a bit more
robust around the deep inguinal ring than at the superficial inguinal ring but there is noted
variation there now important to note here in this image the inferior epigastric vasculature is going
to be medial to the deep inguinal ring and that relationship is something that comes up often
particularly in discussions of inguinal hernias and lastly here is the trusty diaphragm
so this is going to be the left hemidiaphragm and this over here will be the right
hemidiaphragm and we discussed the diaphragm in the previous block but it's just as important
here as a major subdivision between the thoracic and abdominal cavity you can see the liver right
underneath here with that very close relationship in the stomach it's just going to be deep to um oops i have these mess mixed up this should be
the left and this should be the right always patient left and patient right see that that gets
us sometimes uh even though we think about these things quite often so that makes sense because the
liver should be on the right so right underneath the the right hemidiaphragm will be the liver
and right underneath the left hemidiaphragm which you can't see very clearly because it's not
poking out underneath here will be the stomach apologies for for that but you can see kind of
on the fly how we can get those things confused now recall that the diaphragm has three
openings that allow structures to traverse the region uh recall the esophagus is going
to traverse the region you will have also the vagal trunks will be closely related to to that
you'll have the inferior vena cava that will ascend through this region to get to the right
atrium and of course you'll have the aorta which is also going to traverse the diaphragm in
order to get to the abdominal cavity region okay that should wrap us up regarding
the musculature in the session and the inguinal canal structures and contents
please take your time to review and reach out if you have any questions i
hope you have a great rest of your day