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