The spinalis is a muscle located in the back, part of the erector spinae group. It runs along the spine and helps maintain an upright posture. The spinalis is divided into three sections: spinalis thoracis, spinalis cervicis, and spinalis capitis, each corresponding to different regions of the spine. This muscle plays a crucial role in extending and rotating the spine. It works in conjunction with other muscles in the erector spinae group, such as longissimus and iliocostalis, to support movements and stability of the back during various activities.