Final answer:
The three large, complex groups of muscles that extend or laterally flex the vertebral column are collectively called the erector spinae muscles.
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. This group includes the iliocostalis, longissimus, and spinalis muscles. The erector spinae group is responsible for controlling flexion, lateral flexion, and rotation of the vertebral column, as well as maintaining the lumbar curve.