Final answer:
The perineal body is where the mesoderm-derived levator ani and deep transverse perineal muscle merge, each contributing to pelvic support and functions related to urination and sexual activity.
Step-by-step explanation:
The perineal body is a fibromuscular structure in the perineum, and it serves as a central point of convergence for several muscles. In the case presented, two structures that merge at the perineal body are the levator ani, which is derived from mesoderm, and the deep transverse perineal muscle which is also of mesodermal origin. The levator ani is part of the pelvic diaphragm and includes muscles such as the pubococcygeus and the iliococcygeus, pivotal for supporting pelvic viscera and aiding in functions like defecation and childbirth. The deep transverse perineal muscle is part of the deeper layer of the perineal muscles and plays a role in stabilizing the perineal body and ejaculatory function in males.