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
While performing a voiding cystourethrogram on a 45-year-old male, the urologist was too forceful when he inserted the catheter and accidentally damaged the wall of the membranous portion of the urethra in the deep perineal compartment (urogenital diaphragm). Which of the following structures would most likely be traumatized at this location? 
Select and explain. 
A. Bulbospongiosus muscle, B. Sphincter urethra (compressor urethra), C. Corpus cavernosus penis (crus), D. Ischiocavernosus muscle
B: Sphincter urethra (compressor urethra)
Answer: B: Sphincter urethra (compressor urethra) 
Explanation: If the membranous portion of the urethra is injured, urine and blood can leak upward into the retropubic space (of Retzius) limited inferiorly by the urogenital diaphragm and the muscle within (compressor urethra), which would be injured. The bulbospongiosus muscle and other perineal muscles, the corpus cavernosa penis, and the openings of the bulbourethral ducts are inferior and anterior to the region of injury.