 So, this is going to be a demonstration of the colon. The large intestine, we have completely e-viscerated out and we have spread it out here. This is the terminal ilium and we have put a probe inside the opening of the terminal ilium and we can see it is coming out through the iliocecal junction. This is the cecum, this is the ascending colon, this is the transverse colon and this is the descending colon and after that was the sigmoid colon which we have removed. This is a remnant of the castrocholic ligament which is a part of the greater momentum which is coming from the greater curvature of the stomach to the transverse colon. This is part of the transverse mesocolon. These are the parts of the greater momentum that we have retained just to show the continuity. Having mentioned these, I would like to draw your attention to a few basic things about the colon. We can see these dilatations of the wall of the colon. These are called postray or the sacculations. Then we can see this ligamentous structure on the surface of the colon that is known as the tinia coli and we can see it in some places very clearly. The tinia coli is actually condensed longitudinal muscle fibers. Length of the tinia coli is slightly less than the total length of the colon and that is the reason why we have these dilatations which we refer to as the hostrate. The tinia coli are three in number and they are called tinia mesocolica, tinia omentalis and tinia liberea. The naming is based on their location in the transverse colon. The tinia which is in relation to the transverse mesocolon that is called tinia mesocolica. The tinia which is in relation to the greater momentum that is called the tinia omentalis. And the third tinia which is free from either of these is called tinia liberea which is liberated and that is the name which continues for the rest of the colon. At last to the tinia coli we see these fatty projections. These are known as appendices epiploike and really these can undergo torsion to produce a condition known as epiploike appendegitis. Now let's take a look at the interior and see a few of the characteristics. This is the heliosecal opening, opening of the heliop and we have put the instrument from the heliop. We can see it has got a small projection this is known as the heliopapula. In a cadaveric dissection it has got a distinct upper and lower lip and that's why previously it used to be called the heliosecal valve but now we know there is no true valve here it is just a projection with an opening. In this particular cadaver the appendix has been removed so therefore we cannot see the appendix opening where my finger is located this is the most likely place of the opening of the appendix and this fibrous psychiatric that we see here this represents the remnant of the stump of the appendix and we can see a suture here. So this is the stump of the appendix where it has been removed. Now let's take a look at the interior of the rest of the colon. We can see these mucosal folds. These are called the semilunar mucosal folds. Semilunar folds are because of the shortening effect produced by the tinea coli. Now let's take a look at the interior of the transverse colon a section of the transverse colon. This is a section of the interior of the transverse colon and we see some additions are there inside and we can see some pseudo diverticulae here and when I put my finger on to the descending colon we notice that there is a very tight stenosis here. As a matter of fact my finger with a lot of difficulty it has gone in so therefore there is some sort of narrowing in this junction here between the transverse colon and the descending colon. In an endoscopy if we were to see in a living person then we will see that the mucosal pattern inside the transverse colon will be fully circular as opposed to the mucosal pattern in the ascending and the descending colon. This is a colonoscopic view of the transverse colon to show the triangular lumen and the circular mucosal folds. This is a colonoscopic view of the descending colon to show the semilunar mucosal folds and this is an enlarged view of the previous to show the splitting impression at the region of the splitting flexure. So that is the differentiating point between the transverse colon and other places but here we cannot see that. Now let's take a look at the descending colon. We can see these projections here. These are known as diverticulae. The descending colon is known for formation of diverticulae and my instrument has gone into one of them and I'm going to put my instrument in a second one this one. So these are called diverticulae which are more common in the descending colon and they can be a cause of bleeding correct. So these are the findings that we can see from the outside and from inside. Now let's take a look at the blood vessels. Straight away we notice that all around the colon we have this vascular pattern which goes along the margins of the colon. This blood vessel is referred to as the marginal artery. I will trace the marginal artery all the way from one side and we can see it is going all the way around following the margin the vicentric side and it continues and it comes here onto the ascending colon. This marginal artery is formed by the union of the following blood vessels. One, this is the heliocolic artery which divides into an heliobranch and a colic branch which divides into an ascending and a descending. Then we have the right colic artery which divides into a descending and ascending. Then we have the middle colic artery which divides into a right and a left branch and then we have the left colic artery. In this case we see two left colic arteries. The left colic artery incidentally comes from the inferior mesentery artery. All the others come from the superior mesentery artery. The left colic artery also divides into a descending and ascending and finally we of course we have the sigmoid arteries which go to the sigmoid colon. So all these ascending descending right left and ascending descending branches they all unite to form a vascular arcade on the mesentery side of the colon and that is called the marginal artery. And from the marginal artery we can see straight arteries going into the colon and that is how the colon receives its blood supply. The junction between the right two thirds and the left one third the transverse colon up to that much is the midgard supply and from here till the rest is the hindgard supply. So superior mesentery artery is the midgard artery and the inferior mesentery artery is the hindgard artery. So that brings me to one or two words of clinical correlation. Colonic cancer is quite common. Then we will have to do what is known as hemicolectomy. If it's a problem on the descending colon we have to do a right hemicolectomy. If there's a pathology in the descending colon we have to do a left hemicolectomy. In the process of doing hemicolectomy we have to basically ligate these arteries and that is the principle that we have to employ while doing any resection of the colon. And after we have removed it we have to take the stump of the ilium and anastomose it with either the transverse colon or we have to take out the portion of the descending colon and bring it out as a colostomy. Before we conclude let me mention a few words about the iliocecal junction. It's at the iliocecal junction. As we mentioned this is the arterial supply of the iliocecal junction. The iliocolic artery gives an ilial branch. Ilial branch as it descends down. One branch goes in front of the ilium. One branch goes behind the ilium. The branch which comes in front of the ilium is this one here and it raises the fold of petronium where my finger is located. This is referred to as the superior iliocecal fold and this can be a source of internal herniation. Likewise we can see a fold of petronium below the ilium and we can see it here. This is inferior iliocecal fold and this can also be a source of internal herniation. The difference is while the superior iliocecal fold has got a blood vessel inside it and therefore it is more risky to operate the inferior iliocecal fold is bloodless and therefore it is relatively safe and therefore this is referred to as the bloodless fold of trees. To continue with the story the descending ilial branch is the one which gives an appendicular artery which supplies the appendix but in this case as we mentioned appendix has been removed. So these are all the points which I wanted to mention about the colon and its blood supply and the parts of the colon. Thank you very much for watching Dr. Sanjay Sanyal signing out. Dr. Gomthi Chudilal is the camera person. If you have any questions or comments please put them in the comment section below. Have a nice day.