This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen & Pelvis, Subject name: Anatomy
Choose the appropriate lettered structure in this computed tomography scan of the female perineum and pelvis. Which structure is innervated by the nerve passing through both the greater and lesser sciatic foramina? 
Select and explain. 
A. A, B. B, C. C, D. D
B: B
Answer: B: B 
Explanation: (b) The obturator internus muscle and its fascia form the lateral wall of the ischiorectal fossa. This muscle is innervated by the nerve to the obturator internus, which passes through the greater and lesser sciatic foramen.