Which of the following muscles is considered part of the internal obliques in the abdomen?

The internal obliques are a major muscle group located on the sides of the abdomen, underneath the external obliques. They play a crucial role in various movements such as trunk rotation, lateral flexion, and maintaining core stability. The anatomy of these muscles allows them to contribute significantly to the function of the abdominal wall by helping to compress the abdomen and assist with forced expiration.

In this context, identifying the internal oblique muscles is straightforward, as they are defined by their name. The other muscles listed, while important in their own capacities, do not belong to the internal oblique group. The rectus abdominis is known as the "six-pack" muscle and primarily works for flexing the spine. The transverse abdominis acts as a stabilizer for the pelvis and lower back, offering core support rather than lateral movement. The quadratus lumborum is located in the lower back and assists in lateral flexion and stabilization of the pelvis, but it does not form part of the abdominal muscle group that includes the internal obliques. Thus, the identification of internal obliques as part of the abdominal structure is accurate.