This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Development of GU system and Neuro-vascular supply of pelvis & perineum, Subject name: Anatomy
Lower 1/3 of vagina is formed by 
Select and explain. 
A. Mesonephric duct, B. Paramesonephric duct, C. Sinovaginal bulb, D. Mesoderm of mullerian duct
C: Sinovaginal bulb
Answer: C: Sinovaginal bulb 
Explanation: Lower 2/3rd of vagina formed from sinovaginal bulb which comes from endoderm of urogenital sinus. Upper 1/3rd of vagina is derived from fused paramesonephric duct. Mesonephric duct forms the collecting pa or ductular pa of male reproductive system. Mesoderm of Mullerian duct is basically paramesonephric duct.