Chapter 3: Lower Limb

ANTERIOR ABDOMINAL WALL AND INGUINAL CANAL

The wall of the abdomen is composed of many sheet-like layers of fascia, muscle, and aponeuroses, which merge and change at different segments. It is important to understand how these muscle and fascial layers result in the twisting movements of the trunk, as postural issues may be signs of muscle weakness. The abdominal wall is also the clinician's superficial view of the abdominal contents, and its appearance may hold clues to intra-abdominal disorders. Vascular distention, irregular firmness, and localization of pain are all important ways to diagnose disorders of the organ systems within the abdomen. When dissecting, pay attention to the route of the vasculature relative to the surface anatomy, as well as major anatomical landmarks.

1. To remove the skin and superficial fascia from the anterior abdominal wall, make a midline incision from the xyphoid process to the pubis, then laterally along the ala (wings) of the ilia.

2. Identify the external abdominal oblique muscle on the lateral sides of the abdomen. This muscle forms an anterior rectus sheath inferiorly and medially. The anterior rectus sheath will be a landmark for this dissection.

3. Lateral to the anterior rectus sheath and superior to the ilial ala, cut into the external abdominal oblique muscle vertically in order to identify the internal abdominal oblique muscle fibers, which run perpendicular to those of the external abdominal oblique.

4. Cut through the internal abdominal oblique to identify transversus abdominis muscle fibers, which run transversely, horizontally.

1. Open the medial portion of the anterior rectus sheath to reveal the rectus abdominis muscles, which attach to the anterior crest of the pubic bone and the costal cartilages of ribs five to seven and the xiphoid process. Note the tendinous intersections of rectus abdominis, which interrupt the muscle fibers along their length (Figure 3.1).

1. Reflect rectus abdominis from its superior attachment.

2. On the deep surface of rectus abdominis is the superior epigastric artery and vein and the inferior epigastric artery and vein.

3. Just deep to rectus abdominis, superior to the ala of the ilia, is the posterior rectus sheath, composed of the tendinous fascia of internal abdominal oblique and transversus abdominis. Follow this sheath inferiorly to identify the arcuate line, where the sheath stops and only the transversalis fascia is present (Figure 3.2).

1. Replace the rectus abdominis and follow the external abdominal oblique muscle to its inferior aponeurosis, the inguinal ...