PROCEDURE - Inguinal Region

Landmarks across the abdomen most commonly follow the 'quadrant system'. This consists of an imaginary transverse line at the level of the umbilicus (the transumbilical plane) and a sagittal line at the midline. These divide the abdomen into a right upper quadrant, left upper quadrant, right lower quadrant and left lower quadrant. Clinical notes often refer to quadrants to describe the location of clinical complaints (Netter251).

In the clinic you may also encounter the more detailed 'regional system' of nine squares in a tic-tac-toe pattern centered on the umbilicus. This is in less common use than the quadrant system (Netter251).

2. Palpate inferiorly along the mid-axillary line until you find the arch of the iliac crests and the anterior superior iliac spine.
    (Figure240a) (Netter187) (Netter192) (Netter250)

Verify that your previous markings are present at the ASIS landmark or the best guess approximation.

Note if the spine is laterally flexed, the left and right anterior superior iliac spines may not line up precisely (as shown in Figure240a).

Radiology - On a plain film of the pelvis the arch of the iliac crest is a prominent feature. The ASIS forms a distinct 'bump' or point to the and of the iliac crest. (Rad4001)

2. On the pelvic region palpate at the midline just superior to the external genitalia for the pubic tubercles and pubic symphysis, verifying your previous skin marker is present.
    (Figure240a) (Netter250)

Radiology - On a plain film of the pubic tubercles are inferior and at the midline with a hypodense (dark) region between the bones. That represents the cartilage of the pubic symphysis, which due to the lack of calcification has low density similar to soft tissue.  (Rad4001)

3. Start at the midline and begin a superior to inferior incision in the skin approximately 5-10cm long.
    (Figure302)

4. Pick up the corner of the skin at the midline with your hemostats and pull the skin up to begin reflecting inferiorly and laterally, extending the midline incision inferiorly towards the umbilicus.
    (Figure302) (Photo3019)

Find the tissue plane between the hypodermis and the aponeurosis of the rectus sheath. (Figure103)

The rectus sheath is a dense connective tissue sheet (aponeurosis means 'flat tendon') which will be white and glassy in appearance.

As you progress laterally, the aponeurosis of the rectus sheath becomes the most superficial abdominal wall muscle, the external abdominal oblique muscle.

5. When you come to the umbilicus make a small circular cut in the skin around the umbilicus and continue on the other side.
    (Figure304)

Approximately 2-3cm lateral to the midline you may encounter anterior cutaneous nerves that emerge from the rectus sheath to enter the superficial fascia.

Other superficial cutaneous nerves extend from the lateral sides of the body across the abdomen analogous to the cutaneous nerves of the thorax.

These all originate from different levels of the spinal cord forming part of the torso dermatomes  (Netter260). We won't dissect these cutaneous nerves specifically.

6. Continue the midline incision and skin reflection stopping ~1cm inferior to the pubic symphysis.
    (Figure304) (Photo3020)

7. As you reflect skin and superficial fascia partially from the lower abdomen observe the changing organization of superficial fascia layers.
    (Netter252) 

Starting at approximately the level of the umbilicus, the superficial fascia forms into two distinct layers continuing inferiorly (Figure305). 

Identify the fatty superficial layer of the superficial fascia (also known as Camper's fascia) and a deeper layer called the membranous layer of superficial fascia (also known as Scarpa's fascia). The membranous layer of superficial fascia sits superficial to the deep investing fascia/rectus sheath of the abdominal wall (Figure305).

Push your hand laterally into the potential space between the membranous superficial fascia and the deep fascia of the external abdominal oblique using your fingers to help separate the layers as you reflect the skin.

Inferiorly, your fingers should be blocked by fusion of the membranous superficial fascia with the fascia of the thigh (the fascia lata) creating part of the superficial pouch. 

The membranous (Scarpa’s) superficial fascia exists as a distinct entity only in the lower abdominal wall where it forms the outer wall of a potential space between itself and the deep investing fascia of the anterior abdominal wall musculature (Figure306).

The membranous superficial fascia extends inferiorly and posteriorly into the perineum where it is continuous with the membranous superficial perineal fascia (in this region is it also known as Colles’ fascia).

The membranous superficial fascia fuses around the edges of the perineum along the ischiopubic rami and the posterior edge of the urogenital diaphragm forming a delineated compartment. Thus, there is an enclosed fascial compartment around the external genitalia, the superficial perineal pouch.

Infections or bleeding into this potential space can fill that compartment and most easily progress superiorly over the lower abdomen.

8. From the pubic symphysis begin a lateral incision through the skin approximately 2-3cm inferior to the position of the inguinal ligament.
    (Figure307a) (male=Photo3021) (female=Photo3066)

The spermatic cord (in the male) or the round ligament of the uterus (in the female) lies just superolateral to the pubic tubercle. Avoid cutting too deeply into the skin as you begin the lateral incision so that these do not become trisected when you are removing the skin.

9. Extend the lateral incision following a line approximately 2-3cm inferior to the position of the inguinal ligament and ending 2-3cm inferior to the anterior superior iliac spine.
    (Figure307)

This lateral cut is approximately along the groin crease.

It is a common error on superficial examination of a patient to consider the groin crease as marking the location of the inguinal ligament. However, the inguinal ligament line is just superior to this crease (anywhere from 3-5cm depending on the body habitus of the individual).

10. Completely reflect the abdominal skin flap laterally out to approximately the maxillary line, leaving the skin flap attached along the lateral side.
    (Figure307)

11. Palpate to verify the position of the anterior superior iliac spine and pubic tubercle.
    (Netter252)

The inguinal ligament extends from the anterior superior iliac spine to the pubic tubercle. Diagrams commonly accentuate the clarity of the inguinal ligament. It is less distinct in a person (particularly post-embalming), but from the bony landmarks we can recognize the trajectory of the ligament

In anatomy the term 'ligament' is used quite generically for any material spanning or connecting two other structures that are not muscles.

The inguinal ligament is not a distinct object, but rather represents a thickening of the inferior part of the external abdominal oblique muscles tendon connecting between the anterior superior iliac spine and pubic tubercle.

12. Remove any remaining superficial fascia and sufficient deep investing fascia from the lateral aspect of the anterior abdominal wall to identify the muscle fascicles of the external abdominal oblique muscle.
    (Netter252)

The external abdominal oblique is a thin muscle originating from across the lower ribs and the costal margin. It is most distinct towards the lateral sides of the abdomen.

Approximately half-way to the midline the external abdominal oblique muscle fibers end in an aponeurosis that continues to the midline forming the outer lamina of the rectus sheath.

The external abdominal oblique has the 'hands in pants pockets' direction of fibers extending from the ribs and attaches as an aponeurosis to the iliac crest, linea alba, and pubic tubercle. At the midline, the aponeurosis forms the outer lamina of the rectus sheath.

At the pelvis, between the anterior superior iliac spine and pubic tubercle, the aponeurosis of the external abdominal oblique muscle forms the inguinal ligament.

13. Use blunt dissection (or careful scalpel scraping) to clean the inguinal ligament of any remaining superficial fascia starting at the lateral side near the anterior superior iliac spine and working towards the midline.
    (Figure308) (Netter252) (Netter359)
    (male=Photo3022) (female=Photo3067)

As you approach the midline following the inguinal ligament (which runs between the anterior superior iliac spine and the pubic tubercle), you will find a triangular opening in the external oblique aponeurosis just superior and lateral to the pubic tubercle. This opening is the external (superficial) inguinal ring.

In males: the large spermatic cord passes through the superficial inguinal ring proceeding inferiorly towards the testis. You may find a thin layer of fascia extending from the aponeurosis out onto the spermatic cord. Do not follow the spermatic cord into the genitalia at this time.  

In females: the round ligament of the uterus passes through the ring proceeding inferiorly to anchor in superficial fascia near the external genitalia. The round ligament of the uterus is small and upon emerging from the superficial ring immediately separates into small collagen fibers that insert into the fascia of the mons pubis. Do not follow it to the genitalia at this time.

The round ligament of the uterus is variable. The Netter359 illustration of the round ligament is aspirational in size and deceptive in simplicity. In some individuals it will be a distinct bundle that then separates into smaller fibers, whereas in many other individuals it will emerge as individual little bundles that are hard to isolate distinctly. Particularly if the donor has had a hysterectomy (removal of the uterus) the round ligament degenerates and becomes nearly indistinguishable from other tissues with fatty tissue infiltration into the ligament.

You may also observe a nerve emerging from the superficial ring, the ilioinguinal nerve sensory to anterior aspects of the genitalia. In males the nerve lies anterior to the spermatic cord while in females it is difficult to distinguish from the round ligament collagen bundles. (Netter260)

14. At the superolateral end of the superficial inguinal ring examine the organization of the tendinous fibers forming the opening.
    (Figure308) (Netter252)
    (male=Photo3023) (female=Photo3068)

As the inguinal ligament becomes the superficial inguinal ring, the aponeurosis 'splits' to send fibers lateral and medial forming the opening of the superficial inguinal ring. These are called crura.

The lateral crus is the part of the external abdominal oblique aponeurosis lateral to the opening.  The medial crus is the part of the external abdominal oblique aponeurosis medial to the opening. 

The inguinal canal is a space deep to the inguinal ligament through which the spermatic cord (male) or round ligament of the uterus (female) travels through before exiting via the superficial inguinal ring.

The deep inguinal ring is the opening on the inside of the abdominal wall through the transversalis fascia (deepest layer of the wall). This is the entry/exit for the testicular vessels and ductus deferens (male) or round ligament of the uterus (female) to enter the inguinal canal.

PROCEDURE - Rectus Musculature

15. Examine the anterior surface of the abdominal wall at the midline and note the features of the rectus sheath.
    (Figure314) (Netter253) (Photo3069)

The relative ease of seeing the linea alba, linea semilunaris, and tendinous intersections will depend on the individuals muscular tissue mass. In a well muscled individual these may all be readily seen, while in a less well muscled individual they will be indistinct until the rectus sheath is opened.

The rectus sheath is a 'sleeve' of the fused aponeuroses of the external abdominal oblique, internal abdominal oblique, and transversus abdominis. This sleeve holds the superior to inferior orientated rectus abdominis muscle.

Examine the anterior surface of the sheath exactly at the midline and identify the linea alba.

The linea alba is the midline point of fusion of all the aponeuroses and separates rectus abdominis into a left and right muscle.

Examine the lateral edge of the sheath approximately 5cm from the midline and identify the linea semilunaris.

The linea semilunaris is the lateral fusion point of the aponeuroses forming the lateral edge of the rectus sheath.  

In a very well muscled individual, you may observe laterally oriented fibrous bands (typically three) forming tendinous intersection lines.

In some individuals expansion of the rectus abdominis muscle on each side of the tendinous intersections give rise to bulges commonly referred to as 'six-pack abs'. However, the number of bulges can range from four to ten as the number of intersections present varies between individuals.

16. On both sides, starting at the costal margin, use scissors to cut the rectus sheath along the medial edge of the rectus abdominis muscle (approximately 1-2cm from the midline), extending the cut as far as the first of the tendinous intersections (if observed).
    (Figure315) (Photo3028)

Do not cut all the way through the abdominal wall at this point, the goal is to cut through just the anterior wall of the rectus sheath to expose the anterior surface of the rectus abdominis muscle.

17. Lift the aponeurosis of the rectus sheath at your incision point and push a finger/probe between the anterior wall of the sheath and the rectus abdominis muscle to separate the sheath from the muscle.
    (Figure315) (Photo3028)

18. Cut the superior edge of the lifted anterior rectus sheath laterally along the costal margin.
    (Figure316)

This opens the superior edge of the rectus sheath and should allow a flap of the rectus sheath to reflect laterally and inferiorly.

19. Starting at the costal margin, blunt dissect inferiorly separating the rectus sheath from the rectus abdominis muscle reflecting the anterior wall of the sheath laterally working your way inferiorly.
    (Figure317) (Netter253) (Photo3029)

As you separate the sheath extend the midline opening progressively all the way to the pubic crest as you reflect the sheath.

The sheath is firmly attached to the anterior surface of rectus abdominis by the tendinous intersections.

As you encounter these, you may need to insert scissors between the rectus sheath and the anterior surface of the muscle to cut through the tendinous connections freeing the sheath from the muscle. 

20. At the inferior end of the sheath where it attaches to the pubic crest, make another cut laterally through the anterior wall of the rectus sheath such that the entire anterior sheath wall can be reflected laterally exposing the rectus abdominis muscle.
    (Figure318) (Photo3001) (Photo3029)

The exposed rectus abdominis muscle size will vary widely between individuals.

The rectus abdominis muscle inserts into the lower rib cartilages superiorly and to the pubic crest/tubercle inferiorly.

The rectus abdominis muscle is an important positional muscle that can bring the rib cage closer to the pelvis allowing flexing of the spine, as when doing a 'sit up crunch' exercise. It also assists with forceful exhalation and raising intra-abdominal pressure.

21. On one side only, at the level of the umbilicus, along the medial edge of the rectus abdominis muscle push a blunt probe posterior to the muscle mobilizing and lifting the muscle away from the posterior wall of the rectus sheath.
    (Photo3030)

22. On one side only (same side as the mobilized rectus abdominis muscle), transect the rectus abdominis muscle transversely, leaving you with a superior half and inferior half of the muscle.
    (Figure319)

23. Reflect the superior half of rectus abdominis superiorly separating the muscle from the posterior wall of the rectus sheath.
    (Figure319) (Photo3031)

Observe vessels descending along the deep surface of the muscle. These are the superior epigastric artery and vein which arise as continuations of the internal thoracic artery and vein.
(Netter254) (Netter258) (Netter259) (Photo3031)

24. Reflect the inferior part of the transected rectus abdominis muscle to observe the posterior side for the inferior epigastric vessels.
    (Figure320) (Netter254) (Photo3032)

The inferior epigastric artery and vein arise from the external iliac artery and vein (the iliac artery/vein is not yet visible and will be seen in later labs).
(Netter254) (Netter258) (Netter259)

The inferior epigastric vessels anastomose with the superior epigastric vessels within the rectus sheath. These vessels provide a collateral channel through which arterial blood can reach the lower body if the descending aorta is occluded, or a path where venous blood can return to the heart if the inferior vena cava is occluded.

The arrangement of the inferior epigastric vessels defines a region of the abdominal wall called Hesselbach's inguinal triangle (Figure322).

The medial edge of the triangle is the linea semilunaris, the superolateral edge is along the line of the inferior epigastric vessels, and the inferior border is the inguinal ligament.

Inguinal hernias are classified by their relationship to the inferior epigastric vessels, although these classifications are just descriptive as the hernia type has negligible impact on the repair method used.

A direct hernia pushes through the abdominal wall medial to the inferior epigastric vessels (penetrating the fascia/wall breaching through Hesselbach's triangle, more common in adult).

An indirect hernia protrudes lateral to the inferior epigastric vessels extruding through the deep/superficial inguinal ring (most common as a congenital defect).

25. Examine the posterior wall of the rectus sheath at approximately the level of the anterior superior iliac crest to find the arcuate line formed by the inferior edge of the posterior rectus sheath.
    (Figure320) (Netter254) (Photo3032)

In some individuals with a thin rectus sheath, the arcuate line can be indistinct.

Review the organization of the posterior rectus sheath. Superior to the arcuate line the posterior wall of the rectus sheath is formed by fusion of the internal abdominal oblique and transversus abdominis aponeuroses. Inferior to the arcuate line only transversalis fascia is present posterior to the rectus abdominis muscle.
(Figure321) (Netter255)

CLINICAL EXERCISE - Appendectomy

26. Interventions through the abdominal wall to gain access to the abdominal cavity for an appendectomy (removal of appendix) are a common surgical procedure. In the open appendectomy, the incision is made at the 'McBurney point' directly anterior to where the appendix is located.

In this clinical exercise, you have the chance to conduct McBurney incision approach to the appendix in a mock surgical intervention.

For the steps to take:
                              ------ click here ------

PROCEDURE - abdominal contents

27. Replace the previously reflected halves of the rectus abdominis muscle into the normal position.

28. Grasp the anterior abdominal wall tissue with forceps and while lifting slightly make a starter incision ~1cm long superior-to-inferior through the linea alba superior to the umbilicus.
    (Figure323) (Photo3070)

29. Place a probe or finger into the opening to lift the anterior abdominal wall away from the underlying organs so that you can extend the incision superiorly along the center of the linea alba.
    (Figure323a) (Photo3071) (Photo3072)

As the incision becomes longer it will aid to have someone from each side lifting the anterior abdominal wall away from the underlying abdominal organs.

Immediately deep to the aponeurosis of the rectus abdominis (i.e. the linea alba at this location) there is a thin layer of pre-peritoneal fat. This fat layer varies considerably in extent between individuals. Just deep to the pre-peritoneal fat is parietal peritoneum.

30. Extend the midline incision all the way to the xiphoid process.
    (Figure323a) (Photo3073)

The midline abdominal incision is by far the most commonly used incision in abdominal surgery. It allows rapid access to all of the abdominal cavity and is extensible (i.e. it can be lengthened at need). There are no nerves/vessels crossing from left to right, minimizing tissue injury, and the strong edges of the linea alba are a robust structure for suturing closed.

31. Staying in the midline (i.e. center line of the linea alba) extend the midline incision inferiorly to a point 1 inch above the pubic tubercle.
    (Figure323b) (Photo3074) (Photo3075)

The tissue of the umbilicus can be lifted along one side to gain access to the line of the linea alba as is passes deep to the umbilicus.

It is important to stop an inch superior to the pubic tubercle to avoid injury to the bladder.

The bladder is located immediately posterior to the pubic tubercle and typically extends just superior to the pubic tubercle.

32. Insert the blades of a Balfour retractor into the incision on the left and right sides and spread the midline incision widely, locking the retractor open by turning the set screw.
    (Photo3076)

The Balfour retractor is placed with the base oriented inferiorly. In many versions of use a third retractor arm extends from the base, a 'bladder blade'. This bladder retractor secures and protects the bladder. We are not using that arm as it would obscure structures we plan to examine.

In abdominal surgery, typically large self-retaining retractor assemblies are used. These retractors come in a variety of sizes and self-retaining configurations.

Manually retracting the anterior abdominal wall with people holding the opening is possible. However, is really not feasible to do so comfortably for multiple hours of abdominal surgery on a patient. Thus, large self-retaining retractor systems are used.

33. Observe the peritoneal cavity and abdominal organs visible through the opening made in the anterior abdominal wall, in the steps below we will perform an undisturbed abdominal exploration.
    (Photo3076)

An 'undisturbed' abdominal exploration refers to an examination that does not cut any of the abdominal structures. We manipulate, move, lift, and retract structures, but not cut into any structures at this point.

As you explore the structures and connections between organs in the abdomen, keep in mind that previous abdominal surgery or prior disease states in some individuals may have left residual adhesions between structures.

The majority of the abdominal cavity contains the gastrointestinal tract and associated digestive glands. (NetterBP009)

In descriptions of the peritoneal cavity, the terms ligament, omentum, and mesentery refer to folds or reflections of peritoneum. Blood vessels and nerves enter or leave viscera within these folds of peritoneum.

Also, as you examine the abdominal contents below, note that visceral peritoneum covers abdominal organs either partially or completely and parietal peritoneum lines the wall.

The space between organs and abdominal wall makes up the peritoneal cavity. In the living, the space surrounding all of the organs has only a thin film of fluid similar to pleural spaces in the thorax.

This peritoneal fluid normally contains small numbers of immune defense cells such as mast cells, lymphocytes and macrophages. Some disease states result in excess fluid and cells accumulating in this space (this accumulation is generically called ascites).

Radiology - A plain film of the abdominal organs provides very little information about the position of the organs themselves as the soft tissues do not resolve well on a plain film. Air within the stomach (the stomach bubble) and air of flatus within the large bowel may be visible in patients. Plain film are often used for foreign bodies or as a preliminary study before more advanced MRI/CT studies. (Rad3002)

34. Using your hands begin at the superior aspect of the abdominal cavity and find the edge of the liver
    (Figure325) (Netter270) (Photo3077) (Photo3003)

The liver occupies the upper right quadrant and typically extends just across the midline into the upper left quadrant. The bulk of the liver is deep to the ribcage with the inferior margin of a healthy liver extending approximately 1-2" inches inferior to the costal margin.

Thus, to palpate the liver surface you may need to insert your fingers into the abdominal opening and under the anterior abdominal wall and costal margin to gently retract the liver edge.

35. With your fingers feel for the anterior ligaments spanning from the liver to the anterior abdominal wall, the falciform ligament and ligamentum teres hepatis.
    (Figure324) (Netter256)
    (Photo3078) (Photo3079) (Photo3036)

You may need additional retraction with fingers or an army-navy retractor in the upper right quadrant to expose the falciform ligament and ligamentum teres hepatic.

Falciform ligament - On the deep surface of the right upper flap a thin peritoneal fold, the falciform ligament, attaches the anterior abdominal wall to the surface of the liver. The attachment of the falciform ligament divides the liver into right and left lobes.

Ligamentum teres hepatis - The ligamentum teres hepatis is a degenerative string of tissue that exists in the free edge of the falciform ligament from the liver to the umbilicus.

The ligamentum teres hepatis is the remnant of the embryonic umbilical vein. You may see it called the 'round ligament of the liver' in some sources.

36. Lift the inferior margin of the liver and identify the gallbladder.
    (Figure328) (Netter276) (Photo3080)

The gallbladder is located just inferior to the right lobe of the liver and continues posteriorly behind the inferior border of the liver. 

Gallbladder removal is a relatively common surgical procedure, thus depending on the clinical history of the individual there may or may not be a gallbladder present. If the gallbladder is absent in your donor, examine the gallbladder of a nearby table.

The green coloration from the gallbladder is a result of the embalming chemicals interacting with bile inside the gallbladder. This greenish chemical reaction product leaches out and stains surrounding tissues. In the living, the gallbladder actually has a robin-blue coloration. (Photo3065)

Bilious vomit is yellow-green in color  due to the intrinsic yellow-green color of bile itself enhanced by interaction with the acidic chemical contents of the stomach. 

37. Identify the stomach in the upper left quadrant and the body/pylorus regions of the stomach.
    (Figure329) (Netter276)
    (Photo3082) (Photo3081) (Photo3003)

The main (central) portion of the stomach is called the body and the main region we see at this stage in the examination.

The right-most region of the stomach is the pylorus. However, there are no gross anatomic features that allow separation from the body of the stomach. They pylorus is specialized at the cellular level visible only in microscopy sections.

The esophageal entry point to the stomach typically lies deep to the lateral part of the left lobe of the liver. To the immediate left of the esophageal opening is the fundus of the stomach. These regions are not visible at this stage in the abdominal exploration.

38. Palpate the right end of the stomach for the firm muscular tissue of the pyloric sphincter.
    (Figure329) (Netter276)
    (Photo3082) (Photo3081) (Photo3003)

At the right end of the pylorus of the stomach is the pyloric sphincter.  This sphincter regulates the passage of stomach contents into the duodenum. The pyloric sphincter can be felt as a muscular thickening of the wall.

Arching 2.5 cm upward, the first part of the duodenum may be visible or palpable.

The second and third parts are retroperitoneal. These curve around the head of the pancreas and will not be seen until we dissect the area in a later session.

39. Insert your fingers inside the peritoneal cavity following the body wall on the left upper quadrant inside the ribcage and feel for the spleen.
    (Netter276) 

The spleen is found to the left and posterior to the stomach deep to ribs 9-11. Thus, in some individuals it may be difficult to reach at this stage in dissection.

We will return to the spleen in a later lab when the ribcage has been removed and wider access possible.

40. Hanging inferiorly from the lower edge of the stomach is a large fold of visceral peritoneum, the greater omentum.
    (Figure325) (Netter270) (Photo3082) (Photo3034)

The greater omentum extends down from the greater curvature of the stomach, passing in front of the small intestines, and reflects back on itself to ascend before attaching to the transverse colon.

The greater omentum varies greatly in size, content of fat, and in the elderly often has adhesions connecting it to parts of the small intestines. 

41. Using your fingers separate any adhesions so that you can lift the greater omentum and identify the omentum attachment to the transverse colon along the underside of the greater omentum.
    (Figure330) (Photo3085) (Photo3037)

The extent of greater omentum varies widely between individuals and nutritional status.

42. Deep to the reflected greater omentum are the loops of the small intestine.
    (Figure330) (Netter270) (Photo3037) (Photo3003)

These consist of the jejunum and ileum (intraperitoneal) that have numerous loops. The loops and folds of small intestine are rarely as 'neatly' arranged as portrayed in atlas drawings.

Explore these loops and identify their mesentery attachments to the posterior abdominal wall. 

Numerous vessels and nerves run to the small intestines within this mesentery. In a following session we will be dissecting into the mesentery to identify major vessels.

43. Grasp a loop of the small intestine and pull it anteriorly partly out through the abdominal wall opening.
    (Photo3083)

This is a common procedure in surgery in which loops of bowel are gently pulled up and out of the abdomen to gain additional access for whatever procedure is being performed. Intestinal loops are highly mobile and will not be damaged by gentle retraction or manipulation.

44. Using your fingers work along the small bowel drawing the organ through your fingers 'running' along the organ working proximally (towards the stomach).
    (Photo3084)

Run along the small intestine in the proximal direction by drawing the small intestine through your fingers until you reach the point where the small intestine disappears into the retroperitoneal space.

This point is where the 4th part of the duodenum transitions from retroperitoneal to intraperitoneal and becomes the jejunum.

This point is held in place by the suspensory ligament of the duodenum (aka ligament of Treitz) in the mesentary spanning from the duodenum-to-jejunum junction to the diaphragm.

This ligament is where the small bowel transitions to intraperitoneal and serves as the clinical demarcation of upper and lower gastrointestinal tract.

45. Using your fingers work along the small bowel drawing the organ through your fingers running along the organ working distally (towards the cecum).
    (Photo3086)

Run along the small intestine in the distal direction by drawing the small intestine through your fingers until you reach the connection to the large intestine at the cecum (the ileocecal junction).

Once one team member has 'run the bowel', switch roles such that every member of the team undertakes a full length running of the bowel.

The technique of 'running' or 'walking' the bowel is an important part of abdominal surgery, allowing the surgeon to examine the full length of the small bowel for any injury/trauma.

There are no external gross anatomy features that allow identification of duodenum, jejunum or ileum. Thus, these regions are identified based on relative position, the most proximal is duodenum (at the retroperitoneal transition) and jejunum, while distal regions are the ileum.

46. Push all of the small intestine loops to the left and identify the start of the large intestine in the lower right quadrant of the abdomen.
    (Figure330) (Netter272) (Photo3086) (Photo3087)

The large intestine consists of several parts that you should identify.

Cecum - located just inferior to the ileocecal junction between the ileum and cecum nestled within the right iliac fossa. On the surface of the cecum note the tenia coli (longitudinal bands of smooth muscle) and their continuation on the rest of the parts of the colon. (Figure331) (Netter280)

Tenia coli - The tenia coli represent the outer longitudinal muscles that lie on the cecal surface and continue from it through all parts of the colon. When these muscular bands contract, bulges or out-pouches called haustra are formed. (Figure331) (Netter280)

Appendix - The appendix is attached to the inferior end of the cecum. This is often described as 'worm-like' due to the slender long nature of the organ, ranging from 5-15cm length. If you have difficulty spotting the appendix follow one of the tenia coli inferiorly as these all lead directly to the base of the appendix. (Figure331) (Netter280)

In many individuals the appendix may have been removed to treat appendicitis. Additionally, in about 15% of individuals the appendix 'wraps' around posterior to the cecum (a retrocecal appendix).

Mesoappendix - the appendix is secured and supported by its own mesentery, the mesoappendix ("mesentery of the appendix")

Ascending colon - this ascends along the right margin of the abdomen (it is secondarily retroperitoneal). It ends at the right colic (hepatic) flexure. Alongside the ascending colon is a 'gutter' formed by where it fuses with the right wall, this is the right paracolic gutter. (Figure330) (Netter272)

Transverse colon - The ascending colon turns to the left forming the transverse colon that crosses the abdominal cavity to end at the left wall. At the left wall the colon turns inferiorly, with this bend called the left colic (splenic) flexure and is the start of the descending colon. The transverse colon is suspended in the greater omentum and its position can vary between individuals depending on the size of the omentum. (Figure332) (Netter272) (Photo3037) 

In some individuals fat filled peritoneal bags called omental appendices (or appendices epiploicae) may be present within the mesentery covering the colon. These are most commonly found in the transverse and sigmoid colon regions.

Transverse mesocolon - Posterior to the transverse colon, connecting the transverse colon to the posterior wall, is a sheet of mesentery. This sheet is called the transverse mesocolon. (Figure330) (Netter272)

47. Push the small intestine loops to the right and examine the organization of the large intestine along the left quadrants of the abdomen.
    (Figure333) (Netter272) (Photo3037)

Descending colon - The descending colon begins at the left colic (splenic) flexure and extends inferiorly along the left abdominal wall (it is secondarily retroperitoneal). Alongside the descending colon is a 'gutter' formed by where it fuses with the left wall called the left paracolic gutter.

Sigmoid colon - The descending colon forms a 'S' like loop called the sigmoid colon in the lower left pelvic cavity (this is an intraperitoneal structure).

Rectum - the sigmoid colon ends in the rectum (which is not yet visible and will be examined in the pelvis section of the course).

48. Mesentery connections between abdominal organs divide regions of the peritoneal cavity into subdivisions known as the greater and lesser peritoneal sacs.
    (Figure336) (Netter276)

The lesser peritoneal sac is the region of the peritoneal cavity located posterior to the stomach and lesser omentum.

The greater peritoneal sac is everything in the peritoneal cavity that is not located posterior to the stomach.

These spaces/sacs communicate with each other via the epiploic foramen. Push your fingers posterior to the hepatoduodenal ligament, this opening is the epiploic foramen.

For review with your radiology study, observe how the overall organization of the abdomen and structures/spaces would appear in cross sections.
    (Figure334) (Figure335)

Post-Lab Daily Clinical Review Cases

Each lab has several multiple choice practice cases to reinforce understanding of the material within the lab and associated lectures. These are optional to review at home for consolidating and testing understanding.

Case 01

Case 02

Case 03

CHECKLIST

Skeletal Structures

Sternum
    Xiphoid process

Costal margin

Pelvic bone
    Iliac crest
    Anterior superior iliac spine
    Pubic tubercle
    Pubic crest
    Pubic symphysis

Soft Structures

Skin
    Fatty superficial fascia (Camper's)
    Membranous superficial fascia (Scarpa's)
    Deep fascia

Inguinal ligament

Spermatic cord (males)
Round ligament of the uterus (females)

External abdominal oblique muscle
    External abdominal oblique aponeurosis

Rectus sheath

Superficial inguinal ring
    Lateral crus
    Medial crus

Rectus abdominis muscle

Rectus sheath
    Linea alba
    Linea semilunaris
    Tendinous intersections of the rectus sheath
    Arcuate line

Superior epigastric artery and vein

Inferior epigastric artery and vein

Anterior abdominal wall (internal)
    Falciform ligament
    Ligamentum teres hepatis

Stomach
    Fundus
    Body
    Pylorus
    Pyloric sphincter

Liver

Spleen

Gallbladder

Small intestine

Large intestine
    Cecum
    Appendix
    Mesoappendix
    Ascending colon
    Right colic (hepatic) flexure
    Transverse colon
    Left colic (splenic) flexure
    Descending colon
    Sigmoid colon
    Tenia coli

Mesentery
    Greater omentum
    Lesser omentum
        Hepatogastric ligament
        Hepatoduodenal ligament
    Mesocolon
    Lesser sac
    Greater sac