Abdomen Opening

Lab Summary

The structure of the abdominal wall and the peritoneal cavity along with its contents are taught. A video of McBurney’s incision emphasizes the structure of the abdominal wall. The abdominal wall is further emphasized through a layer by layer dissection. The peritoneal contents are presented in an overview including critical four quadrant structures and the course of the digestive tract.

Lab Objectives

Explain the significance of McBurney’s Point.
For a McBurney’s incision, describe the orientation of the muscle fibers as the abdominal layers are encountered.
Describe and differentiate visceral peritoneum, parietal peritoneum and mesentery.
Explain peritoneal and retroperitoneal.
Describe the greater and lesser omentum.
Describe the position and importance of the omental foramen.
Describe the portions of the duodenum.
Describe the major structures in the 4 abdominal quadrants.
Describe the passage of food from the esophagus to the anal canal.

Lecture List

McBurney’s Incision, Abdominal Wall, Abdomen Basics

Anatomy of the Abdomen

The Abdomen Gallery

1.1a) Abdominal cavity is continuous with the pelvic cavity
1.1b) Abdominal structures protected by bone and muscle
1.1c) Parietal peritoneum lines the abdominal cavity. Visceral peritoneum cover the gut tube.
1.1d) Some parts of the Gl tract become retroperitoneal during development
1.1e) Peritoneal regions of the gut tube have a mesentery
1.1f) Peritoneal and retroperitoneal structures
1.1g) The greater omentum (one of the mesenteries of the stomach) covers much of the abdomen
1.1h) Greater omentum removed
1.1i) Ileum and jejunum removed by dividing the root of their mesentery
1.1j) Blood supply of ascending and descending colon is retroperitoneal
1.1k) The peritoneal parts of the large intestine removed (cecum, transverse, and sigmoid colons)
1.1l) Lesser omentum
1.1m) Omental foramen (epiploic foramen of Winslow) connects main peritoneal cavity with lesser peritoneal sac
1.1n) Omental bursa (lesser peritoneal sac)
1.1o) Hepatoduodenal ligament (part of the lesser omentum) transmits hepatic triad
1.1p) Hepatic triad
1.1q) Spleen and its mesentery
1.1r) Duodenum is divided into four parts
1.1s) Bile duct runs through pancreas and empties into the duodenum next to pancreatic duct
1.1t) GI tract summary
1.1u) Parietal peritoneum removed to show the retroperitoneum
1.1v) The three arteries of the gut
1.1w) The arteries and their distribution
1.1x) Hepatic portal system

McBurney’s Incisions

McBurney’s Point

Locate McBurney’s point one-third of the distance from the anterior superior iliac spine to the umbilicus.

Draw a line parallel to the inguinal ligament and through McBurney’s point to mark the planned incision.

Make an incision about 12 cm in length through McBurney’s point parallel to the inguinal ligament to expose the superficial fascia.

2.1a) McBurney’s point
2.1b) McBurney’s incision

McBurney’s Incision

Incise the superficial fascia to expose the external oblique muscle. Note the direction of the fibers.

Continue the incisions to identify the internal oblique muscle, transverse abdominis muscle, pre-peritoneal fat and the parietal peritoneum.

Open the peritoneum and search for the ileocecal junction. The appendix may be retrocecal and difficult to locate before the abdomen is completely opened. Note the appendix on different donors since there may be considerable anatomic variability.

2.2a) Superficial fascia
2.2b) Layers of superficial fascia
2.2c) External oblique
2.2d) Internal oblique
2.2e) Transverse abdominis muscle
2.2f) Pariental peritoneum
2.2g) Mesentery of cecum
2.2h) Retrocecal appendix

Abdomen Wall

Abdominal Skin Incisions

Make a midline incision from inferior to the xiphoid process to two finger breadths superior to the pubic symphysis incising around the umbilicus.

Make bilateral incisions inferior to costal margin as far lateral as midaxillary line. If the chest has been previously opened, use those medial to lateral skin incisions.

Make incisions parallel and two fingers superior to the inguinal ligament. Incorporate McBurney’s incision.

Reflect the skin and superficial fascia to expose the rectus abdominis muscles and external oblique muscles.

Labels (top to bottom): Incision inferior to costal margin, incision around the umbilicus, midline incision, incision superior to inguinal ligament, Pfannenstiel incision — 3.1a) Skin incisions

Abdominal Wall Musculature

Incise the anterior layer of the rectus sheath. Along the inferior lateral margin of the rectus abdominis muscle, identify the inferior epigastric artery as it passes deep to the muscle. Divide and reflect the rectus and follow the inferior epigastric artery on the deep surface of the muscle.

Reflection of individual muscle layers as shown in the video is complex and optional.

3.2a) Superficial musculature of abdominal wall
3.2b) Internal oblique
3.2c) Tranverse abdominis
3.2d) Rectus abdominis
3.2e) Inferior epigastric vessels
3.2f) Inguinal ligament
3.2g) Divided rectus abdominis
3.2h) Posterior layer of rectus sheath
3.2i) Superior epigastric vessels

Abdominal Wall Incisions

Make a midline incision from xiphoid to pubis to the left of the umbilicus through the abdominal wall. Avoid damage to bowel by making a short midline incision and manually assuring bowel location. Use scissors.

On the left, make incisions parallel to the inguinal ligament and superiorly along the costal margin.

Incisions on the right are more complex in order to preserve umbilical remnants on the deep surface of the abdominal wall.

Make a superior incision from the right of the umbilicus to the midpoint of the costal margin.

Make an inferior incision to the midpoint of the skin incision just superior to the inguinal ligament.

Extend these incisions laterally to the midaxillary line along the costal margin and parallel to the inguinal ligament, respectively.

Note Fig 3.3a.

Reflect the flaps to expose the peritoneal cavity.

3.3a) Abdominal wall plan
3.3b) Abdominal wall incisions
3.3c) Abdominal wall flaps
3.3d) Elevation of umbilical remnants
3.3e) Abdominal cavity

Abdomen Basics

Abdominal Quadrants

With the peritoneal cavity exposed consider its contents in relation to four quadrants.

In the upper right quadrant, locate the liver and gallbladder. In the upper left quadrant, locate the spleen.

Lift the greater omentum to locate the cecum and appendix in the lower right quadrant and the sigmoid colon in the lower left quadrant.

4.1a) Superior abdominal quadrants
4.1b) Greater omentum
4.1c) Cecum and appendix
4.1d) Sigmoid colon

Peritoneum and Mesenteries

Identify the parietal and visceral peritoneum.

Locate the mesenteries of the transverse colon and small intestine.

Locate the ascending and descending colon and note they are fused to the body wall.

4.2a) Mesenteries
4.2b) Ascending colon
4.2c) Descending colon

Lesser Omentum (Peritoneal Sac)

Locate the liver and gallbladder in the upper right quadrant.

Retract the liver superiorly to identify the greater and lesser curvatures of the stomach, the first part of the duodenum and the lesser omentum.

Lesser Peritoneal Sac

Place your finger posterior to the free edge of the lesser omentum. Your finger will pass through the omental foramen (epiploic foramen of Winslow) into the lesser peritoneal sac (omental bursa). The foramen is bounded posteriorly by the IVC and anteriorly by the hepatoduodenal ligament which contains the hepatic triad.

4.4a) Omental bursa
4.4b) Hepatorenal pouch

Liver Dissection

Remove the left lobe of the liver by incising along the falciform ligament and left triangular ligament.

With the left lobe removed, identify the regions of stomach: fundus, body, pylorus, and greater and lesser curvatures. Locate esophageal hiatus.

4.5a) Removal of left lobe of liver
4.5b) Stomach

Stomach, Duodenum, and Jejunum

Follow the course of the digestive tract.

Identify the regions of the stomach and the first two parts of the duodenum. Note the second part is retroperitoneal.

Reflect the greater omentum superiorly and follow the duodenum. Identify the second, third and fourth parts and the ligament of Treitz at the duodenal jejunal flexure.

Follow the length of the small intestine from the ligament of Treitz to the ileocecal junction.

4.6a) Stomach and duodenum
4.6b) Ligament of Treitz
4.6c) Small intestine

Colon

Identify the cecum and look for the appendix on its posterior surface.

Follow the ascending colon to the right colic or hepatic flexure and follow the transverse colon on the deep surface of the greater omentum to the left colic or splenic flexure.

Reflect the small intestines to the right and follow the transverse colon to the descending colon, sigmoid colon and rectum.

Abdomen Opening

Contents

Key Structures

Resources

Abdomen Opening

Lab Summary

Lab Objectives

Lecture List

Anatomy of the Abdomen

The Abdomen Gallery

McBurney’s Incisions

McBurney’s Point

McBurney’s Incision

Abdomen Wall

Abdominal Skin Incisions

Abdominal Wall Musculature

Abdominal Wall Incisions

Abdomen Basics

Abdominal Quadrants

Peritoneum and Mesenteries

Lesser Omentum (Peritoneal Sac)

Lesser Peritoneal Sac

Liver Dissection

Stomach, Duodenum, and Jejunum

Colon

Anatomy of Trunk

Abdomen Surface Anatomy

Physical Examination of Abdomen

Review Quiz