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: Surgery
The main barrier for diffusion of LA is: 
Select and explain. 
A. Epineurium, B. Endoneurium, C. Perineurium, D. All of the above.
C: Perineurium
Answer: C: Perineurium 
Explanation: The main barrier for diffusion of LA is the perineurium. Endoneurium / Nerve membrane is the acute site of action and depend on lipid solubility of drug.