Preganglionic parasympathetic fibers of pelvic splanchnic nerves originate from the S2-S4 spinal cord levels. Which is of the following organ is NOT supplied by pelvic splanchnic nerves?
## **Core Concept**
The pelvic splanchnic nerves are part of the parasympathetic nervous system and play a crucial role in the innervation of pelvic organs. They originate from the S2-S4 spinal cord levels and are involved in the regulation of various pelvic organ functions, including the urinary, reproductive, and gastrointestinal systems.
## **Why the Correct Answer is Right**
The pelvic splanchnic nerves provide parasympathetic innervation to several pelvic organs, including the urinary bladder, prostate, seminal vesicles, uterus, and rectum. However, the **ovaries** receive their sympathetic innervation primarily from the ovarian plexus, which originates from the abdominal aortic plexus and superior ovarian nerve. The parasympathetic innervation to the ovaries is minimal or not significant in terms of pelvic splanchnic nerves.
## **Why Each Wrong Option is Incorrect**
* **Option A:** The **urinary bladder** receives parasympathetic innervation from the pelvic splanchnic nerves, which helps in the contraction of the detrusor muscle and relaxation of the internal urethral sphincter, facilitating urination.
* **Option B:** The **rectum** is supplied by the pelvic splanchnic nerves, which provide parasympathetic innervation important for defecation.
* **Option D:** The **seminal vesicles** and **prostate** receive parasympathetic innervation from the pelvic splanchnic nerves, which is crucial for ejaculation.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the pelvic splanchnic nerves are vital for the parasympathetic control of pelvic organs, particularly in functions such as urination, defecation, and reproductive processes. The **ovaries**, however, stand out as an exception due to their primarily sympathetic innervation.
## **Correct Answer:** D. Ovaries.