 Good day everybody. This is Dr. Sanjeev Sanyal, Professor of the Department Chair. So this is going to be a demonstration of the colon. We have removed the small interesting from here. There's a supine cadaver. I'm standing on the right side. Camera person is also on the right side. So before we start the colon itself, there are a few other points which I need to mention to you. Take a look at this peritoneal space where my hand is moving right now. This is called the right paracolic gutter and similarly on next to the descending colon, this peritoneal space is called the left paracolic gutter and both these paracolic gutters, if there's any abnormal fluid collection, the fluid can drain down into the pelvis, which is here. This is the transverse colon. So therefore the portion of the peritoneal cavity below that is called the infracolic compartment and we have removed the mesocolon from here. The portion of the peritoneal cavity above that is called the supracolic compartment. The fluid, any abnormal collection from their supracolic or infracolonic or both, can track down the paracolic gutters and they can come into the pelvis. So this is one point which I want to let you know. Now let's come to the colon itself. So this is the entire colon that we have excised and we have opened it out. This is the terminal ideal, which we have cut. This is the appendix. This appendix, in this particular cadaver, it was touching this muscle here. This is the iliosoas muscle and therefore we already know that in cases of appendicitis, which is the pelvic appendix, it can irritate the iliosoas muscle and can produce what is known as the hip flexion soas sign, also called the cope sign. And if we passively extend the right hip, the patient will have pain. That's called the copes test. So this particular cadaver, though he has a normal appendix, it could have been a soas sign if he had an inflamed appendix. This structure that we see here, where the ilium is opening, this is the secum. The secum is a unique part of the larger distin, which is 7.5 centimetres wide and 7.5 centimetres long, so it's got equal length and width. This is the ascending colon and you can see it is attached here by means of a peritoneal fold. This is called the right phrenocolic ligament, which is attached to the hepatic flexure of the colon. This is the transverse colon, which we have separated out. There was a transverse mesocolon here, a double fold of peritoneum, which we have removed. Then we have again another fold of peritoneum, which is attaching this portion of the colon here. This is called the left phrenocolic ligament, which attaches the sprenic flexure. And we can see deep down this structure is the spleen, so therefore this is the sprenic flexure. And this spleen can produce an impression on the sprenic flexure that we can see through a colonoscope. And thereafter, this is the descending colon. And then it continues as the sigmoid colon. And we can see it is making a lazy S shaped curve. That's the reason why this is called the sigmoid colon. And then it continues into the pelvis as the rectum at the level of S2. So this is the full extent of the colon. Now let's come to a few other parts of the colon. Now if you look very carefully, we can see one band of muscle tissue here. We can see only part of it here. This is what is known as tina coli. What is this tina coli? Tina coli are three longitudinal bands of muscle, smooth muscle on the surface of the colon. They are bundled smooth muscle, longitudinal smooth muscle. And they have been given names according to their location in the transverse colon. They have been respectively called tina mesocolica, tina libera, and tina omentalis. We can see a part of the tina coli here. To trace the tina coli further down, we can see this is the tina coli here. This is the tina coli. The unique thing about the tina coli is that all the three bands of tina coli, they merge at the base of the appendix. So this is useful landmark that we can use during surgery to trace the base of the appendix during appendicectomy if we have difficulty in locating the appendix. The next structure which I will draw your attention to are these fatty bundles that we see here. These are called appendices epiploike. There were many appendices epiploike and we have removed many of them. They are attached to the tina coli. These are covered by thin layer of visceral petonium. Rarely they can undergo torsion and get inflamed and that condition is known as epiploike appendigitis. The next thing which I would like to draw your attention to are these small dilatations of the colon. These are called saculations or hostry. What are these saculations or hostry produced by? These are produced by the slight shortening of the tina coli which is a longitudinal smooth muscle. And therefore it produces these dilatations and constrictions, dilatations and constrictions which are called hostry. And this same hostry will produce mucosal semilunar folds inside the lumen of the colon. So these are three landmarks of the colon that I wanted to bring your attention to. The next thing which I will draw your attention to is the vascular supply. So for that, again, take a look at this arcade of arteries which I will draw your attention to. We can see one arcade here and please follow me. We can see that it is going all the way around. It is continuing around. It is going across. It is going across and then it is continuing to the left side and it is continuing down. It will continue into the sigmoid also though we have not dissected out the mucentry of the sigmoid. This is called the marginal artery of drumwood. And from the marginal artery of drumwood we can see numerous straight blood vessels are going to the colon. Ascending colon, they are going to the transverse colon, they are going to the descending colon. So this marginal artery, how is it formed? It is formed by the branches of the superior mercenary artery for the midcut and branches of the inferior mercenary artery for the hindcut. Where exactly is the junction between the midcut and the hindcut? This is the transverse colon as I told you earlier. The junction between the right two thirds and the left one third of the transverse colon is the location of the junction between the midcut and the hindcut. So the hindcut is supplied by the inferior mercenary artery which we have not dissected out. It comes out from the abdominal artery approximately where my finger is located at the level of L3. But we can see the superior mercenary artery and that we have already removed. This is the superior mercenary artery and this is the superior mercenary vein. The superior mercenary artery is the artery of the midcut. This arises from the abdominal artery as an unpaired visceral branch from the level of L1. And we can see it is crossing in front of the third part of the duodenum. This is the third part of the duodenum. And it is giving off numerous branches. These are the geigenergal and the ileal branch. But let's not focus on that. Let's focus on the branches to the colon. We can see this branch here. This is the terminal branch of the superior mercenary artery. This is called the ileocolic artery. And this ileocolic artery it divides into an colic branch or a secret branch and an ileal branch which we have cut here because we have removed the small intestine. Then we have the next artery coming from the superior mercenary that is this one here. This is right colic artery. Then we have this artery here. This is the middle colic artery. And then we have this artery here. This is the left colic artery which comes from the inferior mercenary. What do these colic arteries do? Each of these colic arteries they divide into an ascending branch and a descending branch. And we can see that very clearly here. We can see the right colic is dividing into an descending branch and an ascending branch. The middle colic is dividing into a right and a left. This branch is dividing into an upper and a lower. And similarly, this is dividing into a descending and an ascending. All these ascending and descending branches, right and left branches, they all form an asthmatic arc. And this forms what is known as the marginal artery of Drummer. And from there the blood vessels go and supply the colon. The venous drainage for the midcut is the superior mercenary vein. And this is the superior mercenary vein. The branches we can see the tributaries. The superior mercenary vein will unite with the superior mercenary vein behind the pancreas and form the portal vein. Again, the inferior mercenary vein is located here where my finger is tracing. But we have not yet dissected out peritonium. We shall dissect out and then we will be able to see it. The two parts of the colon which have got miscentry. The transverse colon, this has got the transverse mesocolon which we have removed as I said. And the other is the sigmoid colon. It has got a sigmoid miscentry which is called the meso-sigmoid. The meso-sigmoid, if you see carefully now, it is inverted V-shaped, the root of the meso-sigmoid. This is one limb of the V, this is another limb of the V and this is the apex of the V. And crossing under the apex of the V will be the left ureter. So therefore, when we are doing any sigmoid surgery, we have to be careful not to injure the left ureter. That brings me to a few other clinical correlations. Cancer of the colon is not very uncommon. Especially the descending colon because the fecal matter is in contact for a longer duration. We can also have sigmoid ovulus. Left side descending colon, we can have sigmoid diverticulosis. So any of these conditions may require excision and anastomosis of the colon. For example, we may require to excise the ascending colon. This is called right hemicolectomy. And then we can anastomose the ilium to the transverse colon that is called iliotransverse anastomosis. We may have to do a subtotal colectomy where we have to remove the two flexures and the transverse colon. And then we can do a colocolic anastomosis. We may have to do a left hemicolectomy. And we can do, like for example, in cancer of the sigmoid, we may have to do anterior resection. And then we can do a colorectal anastomosis. Or we can bring out the terminal colon as a colostomy. So these are some of the surgeries that are commonly performed for the various pathologies that afflict the colon. For each of these surgeries, we have to be cognizant of these branches. And we have to know exactly which branch to ligate so as to remove that segment of the colon. So these are some salient points about the surgical aspects of the colon that I want to bring your attention to. That's all for now. Thank you very much for watching Dr. Sanjay Sanyal signing out. Solomon is the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day. Please like and subscribe.