This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
All of the following structures are located within the carotid sheath, EXCEPT: 
Select and explain. 
A. Internal jugular vein, B. Cervical sympathetic trunk, C. Vagus nerve, D. Internal carotid aery
B: Cervical sympathetic trunk
Answer: B: Cervical sympathetic trunk 
Explanation: The carotid sheath also is a tubular fascial investment that extends superiorly between the cranial base and inferiorly to the root of the neck. The carotid sheath contains the common and internal carotid aeries, internal jugular vein, and vagus nerve . In addition, the carotid sheath contains deep cervical lymph nodes, sympathetic fibers, and the carotid sinus nerve. The cervical sympathetic trunk lies behind the sheath but is not included within it. Ref: Moon D.A., Foreman K.B., Albeine K.H. (2011). Chapter 25. Overview of the Neck. In D.A. Moon, K.B. Foreman, K.H. Albeine (Eds), The Big Picture: Gross Anatomy