Final answer:
The linea alba is formed by the fusion of the internal oblique and transversus abdominis muscles, enclosing the rectus abdominis muscles and contributing to the strength and movement of the trunk.
Step-by-step explanation:
The linea alba is what is formed via the internal oblique and transversus abdominis muscles fusing together. This white, fibrous band is made of the bilateral rectus sheaths joining at the anterior midline of the body.
It encloses the rectus abdominis muscles, known for giving the appearance of "six-pack abs." The muscle layers including the internal oblique, transversus abdominis, and external oblique muscles provide support and allow various movements and rotations of the trunk while also protecting internal organs.