Insertion: Which muscle inserts on the mastoid process?

Insertion: Which muscle inserts on the mastoid process?

• A. Iliocostalis lumborum
• B. Splenius cervicis
• C. Longissimus capitis
• D. Spinalis thoracis

Answer: (C)

The key idea is that a muscle’s insertion location helps determine its action. A muscle that attaches to the mastoid process can influence head position, extending or rotating the head when it contracts. Among the options, the longissimus capitis reaches the mastoid process, making it the muscle that inserts there. It travels from the lower spine and thoracic region up to the mastoid, so when both sides contract it extends the head, and when it acts on one side it can help rotate the head toward the same side. Splenius cervicis does not insert on the mastoid; it attaches to the transverse processes of the upper cervical vertebrae. The iliocostalis lumborum and spinalis thoracis have insertions in the lower back, thorax, or upper thoracic region, not at the mastoid. So the muscle that inserts on the mastoid process is longissimus capitis.

The key idea is that a muscle’s insertion location helps determine its action. A muscle that attaches to the mastoid process can influence head position, extending or rotating the head when it contracts.

Among the options, the longissimus capitis reaches the mastoid process, making it the muscle that inserts there. It travels from the lower spine and thoracic region up to the mastoid, so when both sides contract it extends the head, and when it acts on one side it can help rotate the head toward the same side.

Splenius cervicis does not insert on the mastoid; it attaches to the transverse processes of the upper cervical vertebrae. The iliocostalis lumborum and spinalis thoracis have insertions in the lower back, thorax, or upper thoracic region, not at the mastoid. So the muscle that inserts on the mastoid process is longissimus capitis.