The Semispinalis Thoracis is a muscle located in the back, part of the semispinalis group of muscles. It originates from the transverse processes of the lower thoracic vertebrae and extends upward to insert into the spinous processes of the upper thoracic and lower cervical vertebrae. This muscle plays a crucial role in stabilizing and extending the spine. Functionally, the Semispinalis Thoracis aids in the rotation and extension of the thoracic spine. It helps maintain posture and supports movements such as bending and twisting. This muscle is essential for activities that require upper body mobility and stability.