Cooper Krone Exam 1 Practice Test 2026 – Complete Prep Resource

Muscles that move the head often insert on the mastoid process, so recognizing this insertion helps identify which muscle is involved. The Splenius capitis originates from the lower cervical and upper thoracic spine and runs upward to insert on the mastoid process of the temporal bone (and on the occipital bone nearby). This insertion enables it to extend the head when both sides contract and to rotate or laterally flex the head to the same side when contracting on one side. The other muscles listed do not insert on the mastoid process: trapezius attaches mainly to the clavicle and scapula (and only its occasional upper-facial fibers contact the skull region, not the mastoid), serratus posterior superior attaches to the ribs, and spinalis capitis generally attaches to the occipital region rather than the mastoid process. Thus, the muscle that inserts into the mastoid process is the splenius capitis.