Which of the following is a muscle layer of the anterior and lateral abdominal wall situated deep to the internal oblique muscle?

The transverse abdominis is indeed the muscle layer of the anterior and lateral abdominal wall that is located deep to the internal oblique muscle. It serves a critical role in core stability and is essential for proper intra-abdominal pressure management. This muscle encircles the torso and engages during activities that involve bracing the core or stabilizing the spine. Its deep position relative to the internal oblique means it effectively works in conjunction with other core muscles to support postural alignment and abdominal strength.

Other muscles and structures mentioned, like the rectus abdominis, are positioned more superficially and primarily contribute to flexing the trunk. The lumbopelvic-hip complex, while important in understanding overall core dynamics, does not refer to a specific muscle layer in the context of abdominal walls. The diaphragm, primarily recognized for its role in respiration, is also not situated in the same layer and functions differently in relation to abdominal musculature. These distinctions reinforce why the transverse abdominis is the appropriate and most accurate answer in the context of this question.