The spinalis thoracis inserts on the spinous processes of which vertebrae?

The spinalis thoracis inserts on the spinous processes of which vertebrae?

• A. Transverse processes of thoracic vertebrae
• B. Spinous processes of L2-L5
• C. Spinous processes of upper thoracic vertebrae (T1-T8)
• D. Base of spinous processes of cervical vertebrae

Answer: (C)

Spinalis thoracis is the most medial component of the erector spinae, running along the spinous processes and acting to extend the spine. Its fibers extend upward to insert on the spinous processes of the upper thoracic vertebrae, typically from T1 to T8. This placement enables it to pull adjacent spinous processes together during extension and stabilization of the thoracic spine. It does not attach to transverse processes (which would be characteristic of other muscles in the group), nor to the lower thoracic or cervical spinous bases, making the upper thoracic spinous processes the correct insertion site.

Spinalis thoracis is the most medial component of the erector spinae, running along the spinous processes and acting to extend the spine. Its fibers extend upward to insert on the spinous processes of the upper thoracic vertebrae, typically from T1 to T8. This placement enables it to pull adjacent spinous processes together during extension and stabilization of the thoracic spine. It does not attach to transverse processes (which would be characteristic of other muscles in the group), nor to the lower thoracic or cervical spinous bases, making the upper thoracic spinous processes the correct insertion site.