Trapezius is attached to all structures EXCEPT:
## Core Concept
The trapezius muscle is a large, flat muscle of the back that plays a crucial role in movements of the scapula, including elevation, depression, rotation, and retraction. It is one of the muscles that connect the upper limb to the axial skeleton. The trapezius muscle originates from the external occipital protuberance, the superior nuchal line of the occipital bone, and the spinous processes of the seventh cervical vertebra to the third thoracic vertebra.
## Why the Correct Answer is Right
The trapezius muscle inserts into the lateral third of the clavicle (collarbone), the acromion, and the spine of the scapula. This muscle is attached to the scapula (specifically, the superior angle, the medial border, and the spine), the occipital bone of the skull, and the spinous processes of the lower cervical and upper thoracic vertebrae.
## Why Each Wrong Option is Incorrect
- **Option A:** The trapezius muscle originates from the external occipital protuberance and the superior nuchal line of the occipital bone; hence, it is attached to the occipital bone.
- **Option B:** The trapezius muscle inserts into the lateral third of the clavicle; therefore, it is attached to the clavicle.
- **Option C:** The trapezius muscle also inserts into the acromion and the spine of the scapula; thus, it is attached to the scapula.
## Why Option D is Correct (Implicitly)
- Since options A, B, and C are structures to which the trapezius muscle is indeed attached, and given that the question asks for the structure to which the trapezius is NOT attached, we need to assess each option based on anatomical accuracy.
## Clinical Pearl / High-Yield Fact
A key point to remember is the trapezius muscle's role in scapular movements and its innervation by the accessory nerve (cranial nerve XI), which is essential for understanding both its function and clinical assessment.
## Correct Answer: D. Sternum
The trapezius muscle does not attach to the sternum; its attachments include the occipital bone, spinous processes of the cervical and thoracic vertebrae, and parts of the scapula and clavicle.