Prelab Images - Peritoneal Cavity & Intestines

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Review the bony landmarks of the abdominal cavity.

The pelvic inlet is composed of the following structures: sacral promontory (N157 or TG1-08), ala of the sacrum (N157 or TG1-08), iliopectineal line (arcuate plus pectineal line in plate N486 or TG3-05, pubic body (part of pubic bone between the inferior and superior pubic rami of plate N486 or TG3-04), and the pubic symphysis (N248 or TG5-03). Plate N248 or TG5-03 shows a good view of the entire pelvic inlet and the lumbar vertebrae. Plate N268 or TG5-01 also shows the relationship of the lumbar vertebrae to the abdominal cavity. See the learning module and the "Intestinal Rotations" animation for the embryonic development of the gut.

Step 2. Expose the abdominal organs by making a midline vertical incision. (Play movie)

Plate N247 or TG5-01 shows the abdominal surface where you will need to make a vertical cut from xiphoid process down near to the pubic symphysis (while going around the umbilicus). It may be easiest to extend the cut inferiorly and superiorly from the horizontal cut you made the last lab to avoid cutting too deep. Plate N260 or TG5-06B or TG5-06C reviews the layers of the abdominal wall (peritoneum, extraperitoneal connective tissue, transversalis fascia, etc.).

Step 3. Examine the abdominal contents, identifying organs, mesenteries, and their relationships. (Play movie)

Plates N348, N331 or TG5-42, and N349 or TG5-43 show the parietal (lining the abdominal cavity) and visceral (lining the organs) layers of peritoneum. These layers are continuous with each other and the peritoneal cavity lies between the two layers. Structures that are "peritoneal" or "intraperitoneal" have their surfaces covered with peritoneum and have mesenteries (double layer of peritoneum that anchors the structure to the body wall). Structures that are "retroperitoneal" are behind the peritoneum, although they may have peritoneum on their anterior surface (Ex: duodenum in plate N348 or TG5-29, kidneys in plate N331 or TG5-31, and ascending and descending colon in plate N349 or TG5-43 are all retroperitoneal). Plates N273 and N274 or TG5-29 also show the pancreas and kidneys to be retroperitoneal. In plates N348, N331 or TG5-42, and N349 or TG5-43 the abdominal cavity is the entire region of space between the anterior and posterior body wall and the peritoneal cavity is just the potential space between the parietal and visceral peritoneum. Plate N269 or TG5-12 shows the liver, stomach, falciform ligament, and small intestines. The omental apron, the part of the greater omentum that hangs down from the transverse colon, is seen in plate N269 or TG5-12. Plates N271 and N284 or TG5-12 show the large intestines. Plate N269 or TG5-12 shows the small intestines and plate N306 or TG5-13 shows them attached to "the" mesentery (the mesentery of the small intestines is known as "the mesentery"). Plate N270B or TG5-14 shows the duodenojejunal flexure (where the duodenum becomes the jejunum), and plate N270A and N311 or TG5-14 shows the retroduodenal fossa and the paraduodenal fold, which contains the inferior mesenteric vein. Plate N281 or TG5-15 shows the ileocecal junction. Plates N280A or TG5-16 and N280B or TG5-16 show the jejunum and the ileum. Plate N306 or TG5-13 shows "the" mesentery (of jejunum and ileum) carrying the vascular supply to the small intestines. Plate N271 or TG5-29 shows the attachment of the mesentery to the body wall with the small intestines removed. Plate N348 or TG5-13 also shows the mesentery anchoring the small intestines to the body wall. The learning module reviews the development of "the" mesentery. The large intestines are shown in plates N271 and N284 or TG5-12. Plate N284 or TG5-12 labels the cecum, appendix, ascending colon, right colic (hepatic) flexure, transverse colon, left colic (splenic) flexure, descending colon, sigmoid colon. Plates N271 and N284 or TG5-12 also label the teniae coli (free taenia), haustra (sacculations), and omental (epiploic) appendages. Plate N284 or TG5-14 shows mesentery connecting to the transverse and sigmoid colon, which are peritoneal. The ascending and descending colon are retroperitoneal. Plate N281 or TG5-15 shows the mesentery attaching to the cecum, which is intraperitoneal. Plate N281 or TG5-15 demonstrates the anterior (vascular) cecal fold, ileocecal fold, and the mesentery of the appendix (mesoappendix). Plate N284 or TG5-14 shows the transverse mesocolon and sigmoid mesocolon. The learning module describes the gut development and fusion fascia (this fusion fascia is possessed by the ascending and descending colon and the other retroperitoneal gut structures, duodenum and pancreas).

Step 4. Remove the peritoneum from the right side of the mesentery to expose and identify the superior mesenteric artery and vein and their branches. (Play movie)

Plate N264 or TG5-34 shows the abdominal aorta and 3 of its major branches (celiac, superior mesenteric, and inferior mesenteric arteries) that supply the digestive tract organs. The superior and inferior mesenteric are covered in this session. Plate N306 or TG5-13 shows the intestines pulled to the left like you will need to do in the lab. Then, you can begin digging through the mesentery to find intestinal arteries, arcades, and arteriae rectae (all labeled in plate N306 or TG5-13). Plates N306 or TG5-13, N280A or TG5-16, and N280B or TG5-16 show how the arcades differ throughout the length of the small intestines. Plates N306 or TG5-13 and N307 or TG5-14 trace the superior mesenteric artery and its branches. Plates N300 or TG5-13, N311, and N312 or TG5-28 show the superior mesenteric vein. By removing posterior body wall peritoneum you can find branches of the superior mesenteric artery (ileocolic artery with its anterior cecal, appendicular, ileal, and colic branches; right colic artery with ascending and descending branches; and middle colic artery), which are shown in plates N306 or TG5-13 and N307. Plate N281 or TG5-15 also shows the anterior cecal artery and the appendicular artery.

Step 5. Remove the posterior body wall peritoneum to expose the inferior mesenteric vessels. (Play movie)

By removing more peritoneum from the posterior body wall you can find the inferior mesenteric artery branching from the aorta. Plate N307 or TG5-14 identifies the left colic (ascending and descending branches), sigmoid, and superior rectal arteries. Plate N311 or TG5-14 shows the inferior mesenteric vein accompanying the ascending branch of the left colic artery. Plates N306 or TG5-13 and N307 or TG5-14 can be used to compare and contrast the arteriae rectae from the large and small intestines. Plate N307 or TG5-14 labels the marginal artery connecting all the arteriae rectae of the large intestines. See plate N308 for variations in the colic arteries. Plates N310 or TG5-13, N311 or TG5-14, and N312 or TG5-28 show the superior and inferior mesenteric veins and the hepatic portal system. Plate N266 or TG5-37 shows the lymph drainage of the abdominal cavity. Plates N316 or TG5-36A and N317 or TG5-36B shows the lymph nodes of the small and large intestines that you might find embedded in the mesentery.

Step 6. Examine the jejunum, large bowel, cecum, and ileocecal valve and examine their interiors on plastinated specimens. (Play movie)

Plate N280 or TG5-16 shows the circular folds of the jejunum. Plate N284 or TG5-15 shows the semilunar folds of the large intestine. Plates N282 and N284 or TG5-15 show the ileocecal valve and the labia of the ileocecal valve (282 or TG5-15.