 To understand the regional anatomy of the colon, first the fascial arrangement will be demonstrated. The abdominal digestive tube is extremely long. During development, this tube rotates in a complicated manner. Later, fusion fasciae are formed between the adjacent cirrus membranes. Surgically, these fusion fasciae provide a cleavage plane allowing mobilization of the colon. Lifting the navel, the peritoneum is transversely cut, and then longitudinally cut along the falciform legament, revealing the left and right lobes of the liver. By reflecting the greater momentum and transverse colon, we see the small intestine. And reflecting the small intestine, we note the root of the mesentery. Now we will view the root of the mesentery from the left. With the forceps holding the duodenal jejunal flexure, looking beneath, we see the upper part of the root of the mesentery, as well as the sickle-shaped peritoneal folds and various retroperitoneal fasciae. Close to the left margin of the fold, the inferior mesentery vein ascends and reaches the retro-pancreatic area. Tracing along the root of the mesentery, we reach the cecum. Again, from the right, we note that the greater momentum and transverse colon fuse from the right colic flexure to the left colic flexure. In this diagram of early development, the gray shaded area is the peritoneum. As the greater momentum develops, it is completely independent of the transverse mesocolon. Later, however, these two become joined by fusion fasciae, as seen here in blinking red. Here, the posterior layer of the greater momentum is separated from the transverse colon. This separation is easier during an actual operation. By separating along the cleavage plane provided by the fusion fasciae, we note that the transverse mesocolon is completely separated from the greater momentum. The border of the cirrus membrane and fusion fasciae runs along the lower margin of the pancreas. To facilitate the separation of the fusion fasciae of the colon, we cut and remove the main mass of the liver. The arrangement of the fusion fasciae of the colon is very complicated. Although the lower parts of the ascending colon and descending colon fusion fasciae are rather simple, the higher parts are more complex due to the presence of the duodenum and pancreas. On the right, note the pre-pancreatic fasciae at the lower half of the pancreas head. The separation of these fusion fasciae is demonstrated in the next dissection. Behind the cecum, we cut the transition of the cecum peritoneum and the parietal peritoneum to enter the fusion fascial sheath and to reach behind the appendix as well. And similarly, in the ascending colon, we separate the fusion fasciae. The root of the mesentery is cut. Now, behind the upper part of the ascending mesocolon, we can see the descending part of the duodenum. In front of and behind the duodenum, you can see yellow areolar tissues. These are the pre- and retro-pancreatic fasciae. First, we strip the pre-pancreatic fasciae and the whole root of the mesentery is removed. Now, we have completely removed the fasciae of the right hemicolon. The small intestine and right hemicolon are free and movable with the base axis of the superior mesentery artery surrounded by the duodenal loop. Now, we will observe the retro-pancreatic fasciae at the lower end of the duodenum. We enter behind the duodenal pancreas to strip the right retro-pancreatic fasciae. We have reached the duodenal jejunal flexure. By returning the transverse mesocolon, we clearly note the position of the pancreas. Reflecting this again, a peritoneal fold is seen at the duodenal jejunal flexure. Interestingly, this fold contains the inferior mesentery vein. Similarly, behind the descending colon, we separate fusion fasciae and then pull it to the right. Here, the inferior mesentery vein and the testicular vessels appear to be parallel, yet they are in different planes, previously separated by the fusion fasciae. Here, we enter behind the inferior mesentery vein. Note the communication of the right and left fusion fasciae layers, just in front of the aorta at the level between the origins of the superior and inferior mesentery arteries. Now, we will dissect the renal fasciae. After reflecting the covering peritoneum, we can see the anterior layer of the renal fasciae. The posterior surface of the kidney is also covered by renal fasciae, which can be separated from the fasciae soicae. Although the suprarino gland and kidney appear as one unit covered by renal fasciae, there is areolar tissue between them. Now, in the left side, we will examine the relationship between the renal fasciae and the fasciae covering of the ureter and testicular vessels. The lower renal fasciae includes the ureter. And from the front, we note that the proximal portion of the testicular vessels is also included within the renal fasciae. After crossing the ureter, the testicular vessels continue within the fasciae and then pass through the inguinal canal to finally reach the testis. Finally, we examine three membranous fascial groups. The stomach ciliac group, the intestine mesentery group, and the kidney renal vessel group. Looking separately at their axial point, we find the ciliac trunk to be the axis of the stomach group. The superior mesentery artery is the axis of the intestine group, and the renal artery is the axis for the kidney. The origins of these three arteries are in close proximity at the level of the first lumbar vertebrae. Therefore, in the clinical anatomy of the abdomen, the level of L1 is critical. By careful dissection of the colon, we can examine the lymphatic chains and their convergence towards the superior mesentery artery. Here, with the greater momentum and transverse colon lifted cranially, we see the small intestine. With the mesentery stripped away, we dissect the fatty and areolar tissues sandwiched between the two layers of mesentery. Similarly, we dissect various mesocolons. Lymphatics tend to run along arteries and then converge at nodes located at major arterial branching points. Here is an example. Looking at the ileocolic artery, numerous thin lymphatics are seen alongside the arteries, which originate from the ileocolic artery. Here, lymphatics converge at a lymph node and then lymph vessels ascend along the ileocolic artery to reach the area of the superior mesentery artery. Generally speaking, lymphatics run along arteries. Let us look at the arterial arrangement. This shows the superior mesentery artery and its supply area. And here is the inferior mesentery artery and its supply area. Note the numerous arteries which anestomost to form an artery parallel to the colon. This is called the marginal artery. Near the colon, thin lymphatics first converge at the epi or pericolic nodes, which lie along the marginal artery. These then form a chain, including the intermediate nodes and reaching the principal nodes. Finally, the lymphatics converge at the peri aortic nodes. Here, with the small intestine reflected inferiorly and to the left, we can see the right hemicolon. By reflecting the transverse colon below the pancreas body, we see the superior mesentery artery and vein close to their origin. Looking now at the small intestine, note the numerous vasorecta from the marginal artery. Small nodes lie near the vasorecta. Lymphatics from these nodes first converge near the marginal artery and then run proximal word. Here is the marginal artery of the colon. The vasorecta are more sparse than in the small intestine. Here, the ileocolic artery divides into several branches. The ileal branch, the colic branch, anterior and posterior sequel branches, and the ependicular artery. Interestingly, this divergence point for the ileocolic artery is actually the convergence point for the numerous lymphatics from the ileocecal region. These lymphatics then ascend along the ileocolic artery to reach the superior mesentery artery. Additionally, lymphatics ascend along the right colic artery to reach the superior mesentery artery. Several lymph nodes can be seen. There are three arteries to the transverse colon which can be seen. One runs to the right colic flexure, one to the middle portion of the transverse colon, and one to the left colic flexure. Along the marginal artery and vasorecta, small nodes can be seen. Lymphatics along the right and middle arterial branches reach the superior mesentery artery on the right side. And along the left arterial branch, lymphatics reach the superior mesentery artery on the left side. These lymphatics then communicate with the superior mesentery lymphatics. Looking now at the descending colon and sigmoin colon, we first examine the arterial arrangement. This time, the arteries are from the inferior mesentery artery. We see the obliquely ascending left colic artery, several sigmoid arteries, and also the superior rectal artery. This is the junction point where the marginal artery from superior mesentery artery communicates with that from the inferior mesentery artery. Now tracing the inferior mesentery vein, we know that it does not continue together with the corresponding artery. Rather, the inferior mesentery vein ascends to drain into the splenic vein behind the pancreas. If we trace the marginal artery along the descending colon, we see a few lymph nodes. But close to the origin of the inferior mesentery artery, numerous lymphatics converge, as we saw earlier with the superior mesentery artery. It is important to note that almost all of these lymphatics converge to the inferior mesentery artery and very few accompany the inferior mesentery vein. Now we will look at the relationship of the colon lymphatics to the upper abdominal lymphatics. With the liver and duodenal pancreas reflected to the left, we see the origin of the superior mesentery artery and ciliac trunk surrounded by autonomic nerves as well as lymphatics. Lymphatics along the portal vein reach the aortic cable nodes and just above the left renal vein. If we look near the posterior surface of the pancreas head, we note the well-developed autonomic nerve plexus. Lymphatics run along the superior mesentery artery but outside the nerve plexus to reach the aortic cable nodes just above and below the left renal vein. Now let us look at the anterior surface of the pancreas. At the lower border of the reflected stomach, the right gastroepiploic vessels are seen. The artery comes from the ciliac trunk but the vein descends in front of the pancreas head to drain into the superior mesentery vein. Near the draining point of the right gastroepiploic vein, also the right and middle colic veins drain into the superior mesentery vein. Tracing the right gastroepiploic vessels, we find that the lymphatics run along the gastroepiploic vein rather than the artery. Lymphatics along the superior mesentery vessels have been demonstrated. The autonomic nerve distribution of the colon and the composition of the related plexus will be shown. Here, with the small intestine pulled to the left and after removal of the lymphatics, the small autonomic nerve fibers along the superior mesentery artery and its branches can be dissected. The supplying nerves of the ileocecal region run along the ileocolic artery. Nerves along the right colic artery supply the ascending colon and communicate with those along the ileocolic artery. Three arteries to the transverse colon can be observed. One runs to the right colic flexure, one to the middle portion of the transverse colon, and one to the left colic flexure. Branches from these arteries join to form arterial arcades. If we trace the nerves which run along these arcades, we reach the superior mesentery plexus. With the small intestine shifted to the right, along the aorta, we see the descending branches of the superior mesentery plexus. These nerves join the inferior mesentery plexus. Interestingly, however, these nerves do not continue to the pelvic cavity. From the inferior mesentery plexus, nerve fibers are traced along the ascending branch of the left colic artery to the left colic flexure and also along the lower branch of the left colic artery. We see nerves along the sigmoid arteries as well. Along the superior rectal artery, nerve fibers from the superior rectal plexus are also seen. Let us examine the composition of the ciliac plexus. Nerves from the thoraxic sympathetic trunk pierce the diaphragm and join the ciliac plexus close to the suprarino gland. Parasympathetic fibers run from the posterior vagus. With the digestive organs removed and the inferior vena cava reflected, we look closely at the origin of the ciliac trunk and SMA as well as the complex ciliac plexus between the suprarino glands. Note, each ciliac ganglion lies between the ciliac trunk and the suprarino gland. The communication between the two ganglia is seen. Now we will trace the parasympathetic component, the posterior vagus, between the ciliac plexus and thorax. Note, the anterior vagus distributes to the stomach, while the posterior vagus distributes to both the stomach and the ciliac plexus. Let us now examine the sympathetic components of the ciliac plexus. Looking at the thoraxic sympathetic trunk, we clearly see the greater, lesser, and lowest splanchnic nerves. These nerves could be dissected out because the right cruise of the diaphragm was cut. Looking at the sympathetic composition of the left side with the left suprarino gland and diaphragm reflected, we see behind the ciliac ganglion. Here we trace the direct route of the greater splanchnic nerve between the ciliac ganglion and the thoraxic sympathetic trunk. Let us look at the renal plexus. With the right renal vein cut, we see two renal arteries. One is typical, and one is a supranumerary renal artery, here on the right. The nerves to the kidney are dissected, and tracing these nerves proximally, we reach the ciliac and aortic plexuses. Communication with the suprarino plexus is also observed. We can see the close relationship between the suprarino gland and the sympathetic nerves. If we cut numerous suprarino arteries, we can shift the suprarino gland, leaving only the nerves. The greater splanchnic nerve gives off branches to the gland. The right suprarino gland is cut to obtain a broader view. Now we will remove the diaphragm to view the direct connection of the posterior vagus with the ciliac plexus. The left renal vein is cut and opened to view the abdominal aorta and the complex connections of the ciliac and inferior mesentery plexuses. A thick complex circular plexus surrounds the origin of the superior mesentery artery. Descending fibers of the ciliac plexus enter the inferior mesentery plexus. The lumbar splanchnic nerves send fibers to both the inferior mesentery plexus and the superior hypogastric plexus. Most sympathetic nerves within the plexus originate from the lumbar sympathetic trunk via lumbar splanchnic nerves. These nerves unite near the bifurcation of the aorta to form the superior hypogastric plexus. This plexus divides to send the hypogastric nerve which enters the pelvic plexus. Looking at the critical aortic bifurcation area and here with the psoas muscle removed, the sympathetic trunk is dissected. Communicating branches with the lumbar plexus are seen. We trace the upper lumbar splanchnic nerve to the inferior mesentery plexus. The lower lumbar splanchnic nerve joins the formation of the superior hypogastric plexus. Now in the same specimen, we examine these sympathetic nerves from the left. The communication of the superior hypogastric plexus and the left sympathetic trunk can be detected. Now let us trace the parasympathetic supply of the left hemicolon via the pelvic splanchnic nerves, the pelvic plexus, hypogastric nerve and also the superior hypogastric plexus. Looking at the descending colon and sigmoic colon, we note sympathetic fibers from the ciliac plexus run along the inferior mesentery artery. Let us examine the parasympathetic supply from the pelvic plexus. Here, the pelvic splanchnic nerves which originate from the sacro plexus are seen to join the pelvic plexus. From this plexus, the component runs via the hypogastric nerve and then crosses the inferior mesentery artery to reach the descending and sigmoid colons. The autonomic nerves to various colons have been demonstrated.