Which group makes up the erector spinae?

The erector spinae is a crucial muscle group that plays a significant role in maintaining posture and facilitating movement of the spine. This group comprises three primary muscles: iliocostalis, longissimus, and spinalis.

Iliocostalis is the most lateral muscle, involved in lateral flexion and extension of the spine. Longissimus, situated between iliocostalis and spinalis, supports spine extension and rotation. Spinalis, the most medial component, assists in the extension of the spine and helps keep the vertebral column stable. Together, these three muscles work in concert to support the spine, enhance posture, and enable controlled movements, making them integral to spinal health and function.

The other groups mentioned in the options consist of different muscles that serve various purposes in the body but do not collectively form the erector spinae. For example, rectus abdominis, internal oblique, and external oblique primarily function in trunk flexion and rotation, while semispinalis and multifidus are deeper spinal muscles with their unique roles in stabilization and movement. Thus, understanding the correct composition of the erector spinae is vital for comprehending its function in overall spinal mechanics and health.