This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: GIT 1, Subject name: Anatomy
The narrowest pa of the ureter is at: 
Select and explain. 
A. Uretero-pelvic junction, B. Iliac vessel crossing, C. Pelvic ureter, D. Ureterovesicle junction
D: Ureterovesicle junction
Answer: D: Ureterovesicle junction 
Explanation: The narrowest lumen is where the ureter enters the bladder wall (ureterovesicle junction) and may be responsible for arresting the passage of stones of as little as 2-3 mm. Note: Sometime the question may not have the option of ureterovesical junction, in that case the intramural ureter (the pa inside detrusor) may be taken as the answer.