hello all this is dr alsup and in this video we are going to be discussing
the peritoneum which is always something that seems conceptually difficult but as we
kind of work our way through i think you'll become more more comfortable
so the goal of this video is not to get down into the fine details or specific mesenteries and
omenta but more to discuss what is a mesentery or what is the omentum what even is peritoneum
so more of what these things are some more definitions then we're going to do the
discussions of the specific parts associated with viscera when we get to those organs
so let's start with just what is peritoneum peritoneum is a serous membrane lining the in
fact it's the the largest serious serous membrane of the body and it lines the abdominopelvic
cavity and note that i did say pelvic cavity as well so as it does extend and end in the pelvic
cavity so we'll be talking about that peritoneum even when we move into that region of anatomy
so similar to what we had with the pleura of the thoracic cavity there's going to be a parietal
and a visceral peritoneum parietal peritoneum is attached to the muscular layers of the abdominal
wall so it's going it's going to line those walls of the abdominal cavity and it's going to
be connected by extra peritoneal connective tissue and we talked a little bit about that when we were
talking about the anterior abdominal wall now the visceral peritoneum is going to be firmly adhered
to at least some surface or surfaces if not all of them of abdominal viscera and it's
going to be it's going to suspend that viscera into or within that abdominal cavity region
now the space between the parietal and visceral peritoneum is the peritoneal
cavity this is often referred to as a potential space and Gray's is going to describe it as
of capillary thinness so you can get an idea of just how small we're talking
but it's often depicted as much much larger in images like the one on this previous slide here
obviously you're going to have viscera that's going to invaginate into this area
so the peritoneal cavity is not going to be nearly as large as what you see in illustrations
it does contain peritoneal fluid which plays a role in lubrication to allow that mobility that
you need in the visceral in this region as well as it has some defensive properties now the majority
of the peritoneal cavity is referred to as the greater sac and this is the largest portion it's
going to surround most of the abdominal and pelvic viscera and it's a bit hard to conceptualize with
any image really because you have to imagine the abdominal wall was also here and so that space
between the parietal peritoneum on the wall on the abdominal wall and the visceral peritoneum
that's associated with the organs that would be the greater sac portion of the peritoneal cavity
there's also a lesser sac often referred to as the omental bursa which is located posterior to the
stomach and the lesser omentum so this is your stomach this is the lesser omentum right here
and so it's going to be located behind these structures but anterior to the pancreas so
that it's just going to be just posterior to this and that greater and lesser sac can
communicate or are connected via the epiploic or omental foramen
of winslow so many different names associated with that connection between the greater and lesser
sac all right let's begin to explore how this peritoneum particularly the visceral peritoneum
can be organized into very discrete invisible structures within the abdominal pelvic cavity and
those generalized terms that are used to describe them so let's start with mesentery as it's kind of
the the most important of these mesentery just generalized is a double layer of peritoneum that
attaches intra peritoneal viscera to the posterior abdominal wall so that is how it's going to have
that connection to more retroperitoneal structures specifically neurovasculature
so it's going to allow neurovasculature from the posterior abdominal wall to kind of move through
and actually supply or drain these intraperitoneal viscera also it serves as an anchoring point
much of the abdominal viscera is intraperitoneal and we will be using and we will have a whole
other video regarding what intraperitoneal viscera is but in short intraperitoneal
organs are almost completely covered in visceral peritoneum now mesenteries are often quite visible
and you can often very clearly see neurovasculature associated with it
these mesenteries are usually named um based on their like location and most will have a meso
associated with it so you're you have a transverse mesocolon which is going to be an attachment to
the transverse colon and then you have a mesoappendix that would be attached to the appendix but if you
ever hear someone referring to the mesentery you know this is the a capital t-h-e they are likely
talking about the mesentery of the jejunum and ilium or the majority of the small intestine
and it's named the because of its size it is hard to miss the mesentery during a surgery
or dissection so it'd be this portion here that is connected to that small mesentery
so very large very dominant within the abdominal cavity moving to the omenta
omenta and mesentery are made of the same thing but what is unique is that the omenta all have
some form of attachment to the stomach and the proximal duodenum or the first part of the
first parts of the duodenum all right so therefore it is special and it gets its own name so this is
kind of the key is that you it's basically a mesentery associated with these two structures
now let's start with the lesser omentum which is which is like a mesentery in terms of it being a
double layer of peritoneum it's going to extend from the lesser curvature of the stomach and um
i'm kind of putting that lesser curvature here because that's what helps me remember where it's
located but it also will extend uh to the proximal duodenum so this area right here
is going to be the lesser omentum now once again it can be subdivided into peritoneal ligaments
which are different name for the same thing just broken down into more specific parts
but does give you a better indication of location when you use these terms
so you'll have a hepatogastric which i'm kind of outlining that portion here and then you'll have a
hepatoduodenal all parts of the lesser omentum so we'll come back to this term ligaments in a moment
the greater momentum has some attachment to the greater curvature of the stomach so the the larger
portion of the curvature as well as extending to the proximal duodenum it like the lesser
momentum is is going to be further subdivided into small segments of ligaments the most prominent of
these ligaments is the gastrocolic ligament often referred to as the omental apron and so
this right here is going to be what's referred to as the elemental apron which is a component
of the gastrocolic ligament this is going to hang down like an apron from the greater momentum and
proximal dual duodenum over the small intestines it'll actually cover this small intestine and
then it will loop back superiorly to attach to the anterior surface of the transverse colon
thus this portion of the greater momentum is actually four layers now some people think
that the omental apron is synonymous with the greater omentum as in they're the same thing
but that's not true it is a part of the greater momentum there will be other ligaments associated
with the greater momentum that we'll talk about more detail as we get to those specific viscera
now we keep talking about those peritoneal ligaments so let's actually define it
now ligaments are going to peritoneal ligaments are double layers of peritoneum that connect and
you see i have that in italics so that's a key to understanding what a peritoneal ligament is
so it's connecting viscera with other organs or viscera to the wall so again same thing as
a mesentery or omenta but just a bit more specific in regards to describing what is
connected and these are typically one of those seemingly rare cases in anatomy where
names are helpful i know it doesn't always seem like that so these names are can often be broken
down to tell you exactly which organs they connect so in the case say of the hepato-duodenal ligament
you have hepato which means liver and you have duodenal which means duodenum so
the hepatoduodenal ligament is connecting the liver to the duodenum and again these
ligaments are typically just subdivisions of the larger mesenteries or omenta
lastly i did want to review peritoneal folds even though we have discussed them in another learning
objective video as their name would suggest they certainly do have something to do with peritoneum
so in the case of folds the peritoneum more covers a structure than say connecting them
so they think putting a sheet of peritoneum over an already existing structure and this
structure will create a little bump in that sheet and that is those peritoneal folds
so the most prominent these and we've talked about these are the umbilical folds so you have
that median medial and lateral umbilical folds that are lying over say developmental structures
that are occluded or neurovasculature in the case of the lateral umbilical fold
all right and that brings us to our summary slide which i know contains a bit more information than
typical but this learning objective really defines a lot of the terms that we will
be using throughout the rest of our time in our discussions of gastrointestinal anatomy
most of these terms are describing the same thing so specific areas of peritoneum
what differs are what they connect and where they are located so i highly advise taking some time
to be comfortable with these terms because we're going to be using them throughout the course and
we'll get a bit more specific as we do as you review if you have any questions always feel
free to reach out with any questions and i hope you have a great rest of your day