Back Muscles Practice Test 2026 – The All-in-One Guide to Master Origin, Insertion, Action & Innervation!

Spinalis is the most medial part of the erector spinae and runs along the vertebral column. Its distal attachments reach the spinous processes of the upper thoracic vertebrae, and its capitis portion extends to the skull (occipital region). That makes the insertion on the spinous processes of the thoracic spine and the skull the best match for this question. The other options describe attachments typical for other back muscles (to transverse processes or ribs) or are unrelated (medial malleolus), which don’t fit spinalis.