All are derived from mesonephric duct, except:
**Core Concept**
The mesonephric ducts are paired embryonic structures that play a crucial role in the development of the urogenital system. They give rise to various structures, including the Wolffian ducts, which are essential for the formation of the male reproductive system.
**Why the Correct Answer is Right**
The mesonephric ducts primarily contribute to the development of the male reproductive system, specifically the epididymis, vas deferens, seminal vesicles, and ejaculatory ducts. These structures are derived from the Wolffian ducts, which are induced by testosterone produced by the developing testes. The absence of testosterone in females leads to the regression of the Wolffian ducts, which are replaced by the Müllerian ducts-derived structures, such as the fallopian tubes, uterus, and upper part of the vagina.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the mesonephric ducts do give rise to the Wolffian ducts, which in turn develop into the epididymis, vas deferens, seminal vesicles, and ejaculatory ducts.
* **Option B:** This option is incorrect because the mesonephric ducts contribute to the formation of the ureteric bud, which develops into the collecting system of the kidneys, including the renal pelvis, calyces, and ureters.
* **Option C:** This option is incorrect because the mesonephric ducts do give rise to the mesonephric (Wolffian) ducts, which are essential for the development of the male reproductive system.
* **Option D:** This option is incorrect because the mesonephric ducts contribute to the formation of the ureteric bud, which develops into the collecting system of the kidneys, including the renal pelvis, calyces, and ureters.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the development of the urogenital system is influenced by the presence or absence of sex hormones. In females, the absence of testosterone leads to the regression of the Wolffian ducts, which are replaced by the Müllerian ducts-derived structures.
**Correct Answer: B. Ureteric bud.**