Which of the following muscles is innervated by the lower six thoracic and first lumbar spinal nerves?

The internal abdominal oblique muscle is indeed innervated by the lower six thoracic spinal nerves (T7-T11) as well as the first lumbar spinal nerve (L1). This muscle plays a crucial role in the structure and function of the abdominal wall, contributing to trunk stability and movements like rotation and lateral flexion.

Understanding the innervation of this muscle is important in both anatomy and clinical contexts, as it helps link specific spinal nerves to muscle function. The internal abdominal oblique is part of the core musculature, and its proper function is essential for maintaining intra-abdominal pressure and supporting the spine.

The other muscles listed have different innervation patterns that do not include the first lumbar nerve in combination with the lower thoracic nerves. For example, while the external abdominal oblique is primarily innervated by thoracic nerves, the innervation of the rectus abdominis mainly comes from the lower thoracic nerves, and the transverse abdominal muscle is similarly innervated. Thus, recognizing the specific innervation of the internal abdominal oblique highlights its unique functional role within the abdominal muscle group.