Certified Surgical Technologist (CST) Practice Exam

In a McBurney's incision, which is commonly used for an appendectomy, the first muscle encountered is the external oblique muscle. When the surgeon makes this incision, the direction of the incision follows the fibers of the external oblique muscle, which is oriented in a downward and medial direction. This allows for easier access to the deeper structures while minimizing damage to the surrounding tissues.

The external oblique muscle plays a significant role in abdominal wall integrity and movement, as it is one of the main muscles on the lateral side of the abdomen. Its fibers run diagonally, allowing for the surgical incision to be made parallel to the muscle fibers, thus aiding in a smoother dissection and minimizing trauma.

Understanding the anatomy of the abdominal wall is crucial in performing surgical procedures such as the McBurney's incision, as it helps in identifying and managing the layers of tissue correctly. The other muscles listed, including the transverse abdominis, rectus abdominis, and internal oblique, are encountered deeper in the layer structure after the external oblique is divided.