Lab Manual - Inguinal Region

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Describe the anatomy of the inguinal canal. (explanation)
  2. Describe the anatomy of the various kinds of abdominal wall hernias (indirect and direct inguinal, umbilical, lumbar). (explanation)
  3. Define the layers of the anterior abdominal wall, their contributions to the coverings of the spermatic cord and round ligament, and the origin of these coverings as related to the descent of the gonads. (explanation)
  4. Identify the anatomical landmarks on the deep surface of the anterior abdominal wall and their relationships to the types of inguinal hernias. (explanation)

Readings and Modules:

Procedure:

1. Examine the round ligament of uterus or spermatic cord and inguinal canal. (Play movie; View images: N 259A, 259B, 260, 262, 263387, 390, 400, 497, 498, TG 3-14, 5-08, 5-09A, 5-09D, 5-10A, 5-10B, 5-10C, 6-31)

Review the descent of the gonads in your text. In the inguinal region (male) carefully incise and probe beneath the cremasteric layer (muscle and fascia) from above downward toward the scrotum. On the deep surface of the cremasteric layer, lateral to the cord, you may notice the small genital branch of the genitofemoral nerve. What does it innervate? Note that the cremaster muscle increases in density as it is traced upward toward the superficial ring. Note its continuity with the internal oblique muscle, as well as the manner in which it overlies the cord. In the female, if identifiable, dissect the cremaster muscle within the inguinal canal, removing it from the round ligament of the uterus.

Pull the round ligament or spermatic cord laterally, exposing the posterior wall of the inguinal canal. Examine the falx inguinalis. Note that the falx is composed of fibers of both the internal oblique and the transversus abdominis muscles. Between the falx and the inguinal ligament identify the weak fascia. Does it have a thickened lateral border (interfoveolar ligament)? Deep to the lateral border of the weak fascia locate the inferior epigastric artery and vein. Note the relationship between the insertion of the falx fibers and the attachment of the lacunar ligament.

The covering of the round ligament of the uterus or spermatic cord now is an extension of the transversalis fascia, called the internal spermatic fascia in the male. Trace this layer toward the labia majora or testis and then proximally up to the deep (internal) inguinal ring. What tissue forms the deep ring, and how does it do so? What does the deep ring transmit (male, female)? Locate its position along the length of the inguinal ligament. Review the inguinal canal from deep to superficial rings. Dissect and identify the structures of the spermatic cord: ductus deferens, testicular artery, pampiniform plexus, genital branch of genitofemoral nerve (may be difficult to find). The testicular artery lies embedded within the pampiniform plexus of veins.

2. Incise the complete thickness of the abdominal wall transversely at the umbilicus. (Play movie; View images: N 253, 259, 260, TG 5-07, 5-10A, 5-10B)

Along a transverse line immediately inferior to the umbilicus, completely cut through the anterior abdominal wall, including the deepest layer of the wall, the parietal peritoneum. From the umbilicus inferiorly to the pubic symphysis, cut through the anterior abdominal wall slightly to the left of midline. The anatomy of the inguinal region may now be more easily studied in detail, since both superficial and deep surfaces of the anterior abdominal wall must be seen to appreciate relationships. Some structures can be seen best (or perhaps only) from within the abdominopelvic cavity.

3. Examine the anterior abdominal wall below the incision, defining the folds and fossae in the peritoneum. (Play movie; View images: N 253, 259, 260, TG 5-07, 5-10A, 5-10B)

Along the cut edge of the lower abdominal wall flap, try to identify the sequence of layers, from deep to superficial: parietal peritoneum, extraperitoneal connective tissue, transversalis fascia, transversus abdominis muscle, internal abdominal oblique muscle, external abdominal oblique muscle. Recall that you have already removed the two outermost layers: subcutaneous tissue and skin.

Now lift or pull down on the lower abdominal wall flap, look on its deep surface, and identify 3 upraised folds in the peritoneum created by structures lying just superficial to the peritoneum: median umbilical fold, medial umbilical fold, and an epigastric (lateral umbilical) fold. These are created by the presence of, respectively: the median umbilical ligament (urachus), medial umbilical ligament (obliterated umbilical artery), and inferior epigastric vessels. Note how these form borders for 3 depressions: supravesical fossa, medial inguinal fossa, and lateral inguinal fossa. What are the relationships of the latter two to the weak fascia and the deep inguinal ring?

4. Examine the internal aspect of the inguinal region, defining the deep inguinal ring, inguinal triangle, and associated structures. (Play movie; View images: N 253, 255, 259A, 259B, 262, 261, 263, 386, 389, 390, TG 5-07,5-08, 5-09, 5-10, 5-11B, 5-11C, 5-30, 6-31, 5-33)

Carefully pull the parietal peritoneum and extraperitoneal connective tissue from the anterior abdominal wall to uncover the deep surface of the transversalis fascia. This will also expose the structures in the above-named folds: the urachus (median umbilical ligament), the obliterated umbilical artery (medial umbilical ligament) and the inferior epigastric artery. The term "ligament" here refers to the fact that the adult structure is a fibrous remnant of the functional fetal structure. The inferior epigastric vessels occupy the lateral umbilical (epigastric) fold; but they are not a "ligament" since they remain functional. Define the inguinal triangle.

Separate the peritoneum from the anterior abdominal wall down to the pecten of the pubis and psoas muscle. Remove any extraperitoneal fat in the area of the pecten and deep inguinal ring. Identify the well-defined pectineal and lacunar ligaments from inside the abdominal wall.

With the transversalis fascia intact, note how the inferior epigastric vessels pierce this tissue to enter the rectus sheath on the deep surface of the rectus abdominis muscle. Find the deep inguinal ring just lateral to the inferior epigastric vessels, as the transversalis fascia is evaginated and allows passage of the ductus deferens (or round ligament of the uterus), testicular vessels, and genital branch of the genitofemoral nerve. These structures come together at the deep ring to form the spermatic cord. Review the anatomy of the falx inguinalis, weak fascia, deep and superficial inguinal rings, inguinal canal and inguinal ligament. What is the relationship between direct and indirect inguinal hernias and these structures ?

Define the inguinal canal, noting location, orientation, rings, walls, shape, and relationships. Review the coverings of the spermatic cord. How are they represented in the scrotum? Review the descent of the gonads. Compare the inguinal canal in male and female. To what does the round ligament of the uterus attach? What is its male homologue? What is the scrotal ligament?

Surface anatomy of the abdomen Surface anatomy of the inguinal region

 

Updated: 21 November 2011