Which muscle is innervated by the dorsal rami of spinal nerves?

The correct answer is the multifidus muscle, which is innervated by the dorsal rami of the spinal nerves. The multifidus is a deep muscle of the back located along the vertebral column, and it plays a crucial role in stabilizing the spine during movement. By receiving innervation from the dorsal rami, particularly of the lumbar and sacral nerves, the multifidus is able to actively contribute to spinal stability and support the extensive range of movements of the vertebral column, including extension and rotation.

Each of the other muscles listed also contributes to the complex architecture of the back and is involved in movements of the spine, but they may have differences in the specific nerves that provide their innervation. For example, while the spinalis, semispinalis, and rotatores are all part of the intrinsic back muscles and receive dorsal rami innervation as well, pinpointing multifidus in this context emphasizes its particular role in deep spinal stability and its specific segmental innervation pattern. This highlights the functional importance and anatomical relevance of the multifidus in relation to spinal health and biomechanics.