hello everybody and welcome back to another Anatomy tutorial today we're going to be discussing the peritoneal cavity I'm going to show you how we can separate the peritoneum into multiple distinct spaces and then we're going to look at some of the intra-abdominal organs that fill the peritoneum itself I'm going to show you how to identify all of these on a CT scan as well as looking at some diagrams here to make our understanding a bit clearer there's a lot of folding and rotating that happens in the abdomen that makes it sometimes quite difficult to know where we're dealing with or what space we're in hopefully by the end of this talk you'll be able to comfortably know where you are in the abdomen which space the various organs are occupying so let's have a look at this sagittal section through a female patient it's obviously a schematic drawing we've got at the top here our lung fields in represented in this orange yellow color here then this green section here is our peritoneum the peritoneum has a layer that touches the abdominal border here this Green Layer wraps around our pelvic organs we've got our uterus here our bladder here and the rectum posteriorly and then goes along this posterior abdominal wall here this is all known as parietal peritoneum it's represented by this green line here the peritoneum also then invaginates in towards the peritoneal cavity and wraps itself around the various organs within the abdomen and that's represented by this double orange line here that goes around the intra-abdominal organs that's what's known as visceral peritoneum so we've got parietal peritoneum on the outside of the abdominal wall and as we head inwards and we wrap around the organs that's what's known as our visceral peritoneum then these parts that head out towards the various organs you can see they're a double layer this here is our transverse colon if you imagine the transverse colon spreading away from this parietal peritoneum pushing through and reaching into the abdomen it's created a double layer of peritoneum now a double layer of peritoneum that comes out from the abdominal wall and heads to a hollow viscous is what's known as mesentry now there are four different mesen trees within the abdomen we've got our transverse mesocrolon mesentry we've got our small intestine mesentry we've got our sigmoid mesentry and we have a little bit of mesentry going for our appendix our appendicial mesocolon mesentry then peritoneum that goes from the stomach which is represented in Orange here towards other organs such as the liver the spleen and our transverse colon that is what's known as momentum we sometimes call these ligaments any double old of peritoneum we can also call it a ligament and here we have between our stomach and our liver we've got our gastro hepatic ligament or otherwise known as our lesser omentum then from the stomach hanging right down the front of the abdomen folding back up so we've got four layers of peritoneum here going back up to the transverse colon that's what's known as our greater momentum so we've got less momentum at the top greater momentum at the bottom you'll see that we've got a couple of retroperitoneal structures behind the peritoneum we've got our abdominal aorta coming here giving off our Celiac our SMA and our IMA we've got a whole lecture a whole talk on the abdominal aorta and its various branches if you haven't checked it out I'd highly recommend going to look at that it really intricately matches what we're looking at here in this abdominal CT we also have our pancreas here that wraps around this is the Antonette process of the pancreas up to the body here wrapping around the SMA as we're going to see in our CT scan as well as some of the bowel is also retroperitoneal so our second or fourth part of the duodenum as well as our ascending and descending colon all our retroperitoneal structures so we're going to have a look at a CT the first thing I want to do is identify the various organs that fit within the abdominal cavity then we're going to go back to a diagram and I'm going to show you how we can separate the peritoneum into multiple different spaces and then go through another CT where I can show you how to identify those spaces so let's start by having a look at a normal axial slice CT scan so whenever you're looking at the abdomen on a CT scan it's best to start in the thorax and head your way into the abdomen so you don't miss things on those uppermost portions of the abdomen so you can see here we're in the thorax we've got our heart centrally we've got our right and our left lungs the patient's front is here anterior posterior divertible column this is their right side and then that is their left side there so we can scroll down into the abdomen the first thing that we see is the top portion of the liver here we know that our right Hemi diaphragm is slightly higher than our left because our liver is occupying space within that right Hemi diaphragm so let's scroll down through the liver what I want to do first is have a look at the gastrointestinal tract I want to show you how you can follow it all the way from the esophagus all the way down to the rectum and then we can go back up and look at various different organs within the abdomen so we've got our liver on the right and we can see our spleen coming in on the patient's left and what I want to do is start at the esophagus and work my way down so let's go down the esophagus the esophagus is going to pierce the diaphragm it's going to move in to the stomach we can see the stomach here note its relation to the liver and to the spleen we follow the stomach it should make this J shape around head on to the patient's right hand side become the pylorus and then into the first part of the duodenum here I can follow with my mouse the duodenum there in the first part heads backwards to Port towards the retroperitoneal space you can see how it comes backwards here this now becomes the second part of the duodenum which heads inferiorly so let's keep scrolling inferiorly this part of the duodenum is now retroperitoneal it doesn't have its own mesen-free supplying it it's just got parietal peritoneum over the front of it here can follow that duodenum now it should then head across the midline of the patient that is our third section of the duodenum and then once it's headed across it heads back up superiorly so let's scroll up superiorly we can follow that duodenum here and we should get to a turning point you see this Turning Point here that's what's known as our DJ Fletcher and that's where the ligament of trites is our duodenum there in the fourth part now becomes the jejunum so we can then see our judging them here and I'm not going to follow all the small bowel Loops exactly down but we can keep scrolling inferiorly and we can see that these small bar Loops coming across the abdomen and we can see these blood vessels all coming through the mesentry towards that small bowel all of this small bowel is in the peritoneal cavity taking up the majority of the space centrally so we can scroll all the way down this patient doesn't have much intra-abdominal volume here you can see all these small bowel loops and those small small bowel Loops head all the way down into the pelvis here we can then follow the last bits of the small bound our Ilium follow it back up and we should see this coming into our cecum here we can see here the small bar Loops follow it here comes into this more dilated section here I'll see him and we might be able to just see our ileocecal valve so now that we're in our secant we can go and look for our appendix we should see a small out pouching we can see posteriorly here if we follow this out parching let's see it from its roots follow it out we can see it coming superiorly here heading all the way up it should be a hollow blind ending tube let's go up you can see some air in it keeps scrolling up and it should it goes all the way up towards the liver here and it ends there so it's quite a long appendix it's behind the sequence a retrosecal appendix heading up towards this inferior portion of the liver let's follow that appendix back down to our second and seeing it inserting there let's follow the C come up this is now our ascending colon I mentioned to you the ascending colon doesn't have its own mesentry it's actually technically retroperitoneal although when we doing surgery and we go into the abdomen the ascending colon and the descending colon kind of act like intraperitoneal organs but they actually are technically retroperitoneal they don't have that masonry supplying them so let's scroll upwards follow the cecums now becoming our ascending colon that should head all the way up right into our hepatic flexure where our ascending colon then becomes our transverse colon so here is our hepatic flexure we should be able to follow that across now and there is our transverse colon coming all the way across the abdomen there our transverse colon heads across and that then that should also go up towards our splenic flexure before it becomes our descending colon so let's head up superiorly we should see this transverse colon coming higher and higher towards the spleen here it wraps around and then we can see it come into here the most Superior portion of that transverse colon and then it comes down into our descending colon you can see how this is retroperitoneal we've got our peri-renal space here filled with fat and in next week's lecture I'm going to be discussing the retroperitoneal structures and the various fascia that runs through the retroperitoneum but we can see that this lies in the retroperitoneal spaces no separate mesentry following that descending colon so let's follow the descending colon all the way down and that should keep going down that patient's left hand side and eventually become our sigmoid colon which actually as we mentioned earlier has its own mesentry the sigmoid is an intraperitoneal structure so we see it coming forward here and now you can see a couple of blood vessels coming towards it it's now transitioning into the sigmoid column those blood vessels are traveling through that sigmoid mesentry let's follow it it sometimes crosses the midline you see it crossing the midline here and then we can follow that all the way around back towards the rectum now and we can follow the rectum all the way down there to the anal canal now while we're down here there's a female patient here's the rectum anteriorly to that is the vagina and anteriority to that is the bladder this patient doesn't have a very full bladder we can see the bladder there as we scroll superiorly the vagina now becomes the uterus and we can also see Fallopian tubes and ovaries there so let's head our way now all the way back up we've followed the gastrointestinal tract all the way down let's have a look quickly at the liver and the spleen we've got the liver on the patient's right hand side here we can see the cordate lobe the left and right lobes of the liver I'm not going to go into this in detail I've got a whole talk discussing how to segment the liver into its eight different segments I'll link it above highly recommend going through that if you don't know how to separate the liver into the liver segments and then we've got our spleen that's posteriorly here we can see it with our splenic vein and torturous splenic artery coming that way and again if you don't know the blood supply to these organs I've got a torque on the abdominal aorta that'll also recommend watching if you don't know the blood supply well of the abdomen Okay so we've gone through a basic rundown of the abdomen on these axial CT slices now I'm going to show you how we can separate this peritoneum into different spaces that become clinically important and become important when we're writing reports on our CT abdomen so here we can see our sagittal section now I'm going to go across into an axial section this is the axial slice that I want to eventually look at but I first want to talk about the foregat and how it rotates in utero now initially we have our four gut and hind gut supplied by our Celiac our SMA and our IMA our foregat has both a dorsal mesen tree and a ventral mesentry it's got peritoneal folds that come posterior and attach all the way anteriorly now at the level of the duodine in this first bit of the duodenum that ventral mesen tree falls away and we only have a dorsal mesentry as I've represented up here so if you think of this blue structure as being from the duodenum downwards it's only got dorsal mesentry we've got no mesentry attaching it to the front now this first part of the abdomen I've got three different colors here anteriorly here I've got the liver in the middle I've represented the stomach and at the back here I've represented the spleen and what happens is that rotates 90 degrees anti-clockwise and this the way we're looking at it now it's anti-clockwise 90 degrees so the liver forms on the left hand side of our image would be the right hand side of the patient then the stomach and then the spine we can see how that four gut rotates 90 degrees in this plane here okay when we look at the mid gut later it's going to be rotating 90 degrees in this plane but here we've got 90 degrees on our horizontal plane and with that rotation if we look at an anatomical view of the foregat our liver is now on the left this ventral portion of mesentry that comes across here is now the falsiform ligament then we can see the connection between the stomach and the liver is our gastro hepatic ligament otherwise known as the Lesser momentum that we looked at before the Lesser momentum on that lesser curvature of the stomach going towards the liver and then a gastrosplenic ligament forming here and spleno renal ligament at the back we can see how that rotation happens and what that does is it separates our abdomen we can see we had a left and a right hand side of the abdomen separated now we've got an anterior and a posterior this anterior side is what becomes our greater Sac of the peritoneum and this posterior side this side represented here in front of our pancreas and behind our stomach and liver there that's what's known as the Lesser Sac so now we divided our abdomen into a greater sac and a lesser Sac you can see the peritoneum coming forward round like this behind that that's our retroperitoneum with our kidneys our adrenals our aorta and our IVC as well as our pancreas coming across you can see our vertical bodies at the back can have a closer look at that you can screenshot this if you want to remember that rotation how the liver has now become on the right hand side of the patient and the spleen has come down to the left now guys I don't often ask people to like the videos or share the videos with their friends but I've spent my whole weekend doing these diagrams I'm not an artist by any means I'm hearing from you all that it's really helping so I'd really appreciate if you liked the video subscribe to the channel and maybe leave a comment below so now we've got our sagittal section on the left and we have our axial section on the right and you can see what I described as the Lesser Sac here posterior to the stomach is here our lesser Sac let me draw it in here our lesser Sac extends from this lesser momentum here through the greater momentum here here's the mesentry of the transverse mesocalon this whole section here is our lesser Sac of the abdomen all of the rest of the peritoneum all of this here extending this way all of this is part of the greater SEC we can then also divide the peritoneal cavity into the Supra mesocolic region above the transverse mesocolon and the infra mesocolic region so we divide it into lesser and greatest acts that's kind of an anterior and posterior Division and then below the transverse colon we can describe anything below that as being Infamous colic and anything above that as being Supra mesoconic now we can look at an anterior view of the abdomen we've got our liver on the patient's right we can see our lesser momentum coming from the Lesser curvature of the stomach heading up towards the liver we can see our gastrosplenic ligament there as well and then we can see anteriorly this big apron of mesentry four layers of peritoneum coming down we're looking at this section here that's covering our small and large intestines when you open up in surgery and you've got that big fatty apron that you can lift up that is our greater momentum so we've got our lesser momentum at the top greater momentum at the bottom going off the greater curvature of the stomach and you remember from our abdominal aorta lecture we've got our right and our left gastroepiploic arteries epiploic meaning referring to the momentum what you can notice here as well is that our lesser momentum comes to an end here that's where our four gut ends at the beginning of that duodenum here and we get what's known as the free edge of the Lesser momentum here if you open up an abdomen and surgery you can actually put your finger behind that free Edge and you'd be entering the Lesser Sac you can see the free edge here heading towards the liver so it we actually have this lesser momentum can be called our gastro hepatic as well as a hepatitude or ligament here and there's really important structures that pass through here we've got our common bile duct as well as our hepatic artery and our portal vein and that opening that epiploic foramen or our epiploag foramen of Winslow is what connects the Lesser Sac to the greater Sac within the abdomen they're not two distinct spaces fluid can track between those two two spaces and that is where it will happen so let's take away that apron let's lift it away and we can see our small intestine I told you I'm not an artist and by this stage I've just chosen to abstractly represent the small intestine and then our large intestine our ascending transverse descending sigmoid and rectum now we talked about a 90 degree rotation in the foregat you can see here if this was once a straight tube there's now been a full rotation like this in the vertical plane a full rotation 270 degree rotation all the way around like that so our jejunum our ilium our ascending transverse descending colon has rotated 270 degrees on itself and what that has done is the mesentry that's supplying the small intestine as well as our transverse colon has also rotated and if we think about where that mesentry is coming off the posterior surface of the patient it follows this diagonal course here we've then got our ascending colon which doesn't have mesentry and then we've got a horizontal plane of mesentry coming to our transverse mesoconon like that and so we've separated now this infra mesocolic region into a right hand side and a left-hand side you can see on the right hand side this space here between the root of the mesentry of the small bowel and the ascending colon this space here is our right infra mesocolic space to the right hand side of this ascending colon this is what's known as our right paracolic gutter on the left hand side by the descending colon we've got our left paracolic utter and here separated by this mesentry of the small intestine is our left infra mesocolic space so we've looked at the infamous colic space and now we can see that these paracolic gutters head up towards the spleen and the liver and the space between the liver and the diaphragm that potential space is what's known as our right subphrenic space and the same on the left hand side between the spleen and the diaphragm is our left subphrenic space we've got a couple of potential spaces on the sagittal section we have our rectum coming towards our uterus here this is our recto uterine space otherwise known as the pouch of Douglas really important because it's gravity dependent if we were to have fluid in the abdomen here it would fill this space here in males we have a recto vesicular space because there's no uterus here just between the rectum and the bladder and there's a single space a the rectal vesicular space in females we have a utero vesicular space that can form here when the bladder gets large like that we also have an anterior recess which is kind of can seen that can be seen as another space so we've identified all of these on a schematic let me show you how you can see them on a CT scan so the way I'm going to show you these spaces is by using pathology normally these spaces kind of act as potential spaces the organs are abutting against each other there's no real fluid in those spaces and it's only when we develop fluid or a mass that expands those spaces is it easier to see on a CT scan so again let's start in the thorax and scroll our way down we can see the liver on the patient's right we can see this fluid density encircling or encasing the liver here and this is in the right sub forenic space the same on the left hand side is fluid surrounding the spleen here this is our left sub forenic space we've got our left and our right sub forenic spaces we scroll down inferiorly we should see the stomach forming following that J shape towards the duodenum and then we can see our pancreas which which we know sits in the retroperitoneum and in between the stomach and the pancreas has the expansion of this potential space the Lesser Sac we can see this circular Mass filling that space and this mass is within the Lesser sac I'm going to use another case to show you the greater momentum and then the spaces in the infamous colic space so we can see here let's again scroll to the top of our image again we've got grow societies filling the right and left sub forenic spaces we've got our stomach here filled with fluid and as we scroll down we can see on this anterior surface we've got this mottled appearance of our momentum and we can follow that momentum that apron all the way down follow it down the abdomen we can see it here hanging within the fluid that's filling the abdomen this is what's known as a mental caking when we've got soft tissue density deposits within the fatty momentum normally there should be fat like this the density should look like this but we've got this soft tissue density in our momentum here as I'll scroll up you can see the blood vessels going towards our small bowel Loops here and this color here this is our fluid that's filling the space this is fat density our mesentry going towards our small intestine we can see those spaces are filled with fluid now if we look on the coronal view I'm going to scroll to the back of the patient here we can actually see our Infamous colic spaces so let's scroll forward slightly so I'm posterior at the vertebral column we can see our kidneys here spleen and liver scroll slightly forward and what we'll see is us our small intestine mesentry here heading out towards the small intestine and you can remember from that diagram how the root of that small intestine masonry divides the infamous colic region into our right and our left Infamous colic region so here we can see our left Infamous colic space here and our right Infamous colic space and these spaces heading up the right and the left hand side of the patients are our paracolic gutters it's quite easy to see that if we had say a splenic laceration or bleeding from the liver we're likely to get that blood tracking down the paracolic gutters and not wrapping around the small intestine because this is the potential space so this is the space that things would communicate between the Supra mesocholic and the infra mesocolic spaces now if I head on to the last case I'm going to go back to that normal case and I just want to show you those spaces within the pelvis again we'll use an axial slice and I'm going to scroll right down to the pelvis and we can get our orientation here so let's find the rectum go down to the anal canal in front of the rectum or in front of the anal Canal is our vaginal canal and in front of that will be our bladder now this patient doesn't have a very full bladder so it's a small bladder at the front as we scroll superiorly we can see the vaginal Canal becoming the uterus here and our uterus we can see Fallopian tubes and ovaries on either side and then our rectum posteriorly now between the rectum and the uterus that's our pouch of Douglas here and between the uterus itself and our bladder that's what's known as our utero vesicular space and in males it's a recto vesicular space there's no huge risk in between the two and we'll see in the in males we'll see the seminal vesicles hitting posterity so it's a lot to cover we've discussed the abdominal organs that fill the peritoneal cavity we've seen how we can divide the peritoneal cavity into a lesser sac and a greater Sac as well as dividing it into a Supra mesocholic space which has our right subfrenic our left subphrenic and our lesser Sac filling that space and our infra mesoconic space which has our paracolic gutters as well as our left and right infra mesocolic space as we head down towards the pelvis we've got our rectal vesicular space in men or a rectal uterine space a part of Douglas and the utero vesicular space in women it's a lot to get your head around the rotation of the gut but give it time when you're going through the scans really look for the mesentry heading out towards the small intestine the transverse colon the sigma void in the appendix as well as looking at the potential spaces that surround the different organs now remember there's only about 50 milliliters of fluid in a normal peritoneum 50 to 75 millimeters so you really shouldn't be seeing a lot of fluid filling the spaces and if you see fluid then you need to go and look for a cause whether it be an oxidative process or a translative process so I hope that's helped I'd highly recommend going and watching some of the other abdominal Anatomy videos and next week we're going to be discussing the retroperitoneum so hopefully that will fit all nicely together the structures anterior to that varietal peritoneum as well as the structures posterior to it so I hope you've enjoyed this lecture found it useful in some way and I'll see you all in the next video goodbye everybody