Final answer:
The three large, complex groups of muscles that extend or laterally flex the vertebral column are collectively called the erector spinae muscles. These muscles work together to control movement and maintain the curvature of the vertebral column.
Step-by-step explanation:
The three large, complex groups of muscles that extend or laterally flex the vertebral column are collectively called the erector spinae muscles. The erector spinae group comprises the iliocostalis (laterally placed) group, the longissimus (intermediately placed) group, and the spinalis (medially placed) group. These muscles work together to control movement and maintain the curvature of the vertebral column.