## **Core Concept**
The neurohypophysis, also known as the posterior pituitary, primarily receives its blood supply from the posterior hypophyseal arteries. However, its venous drainage is unique and involves specific routes that differentiate it from the anterior pituitary. Understanding the venous drainage pathways is crucial for comprehending neuroendocrine regulation.

## **Why the Correct Answer is Right**
The correct answer involves understanding that the neurohypophysis primarily drains into the **inferior hypophyseal veins** and then into the **intercavernous sinus** and subsequently into the **cavernous sinus**. Another key pathway involves drainage into the **basal veins** and then into the **great cerebral vein of Galen**. The **portal system** is notably associated with the anterior pituitary, not the neurohypophysis. Therefore, the correct answer relates to the exception in venous drainage pathways specifically associated with the neurohypophysis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option might suggest a known pathway related to the neurohypophysis, making it an incorrect choice as it does relate to its drainage.
- **Option B:** Similarly, this could represent another accurate pathway for venous drainage of the neurohypophysis, thus not being the correct answer.
- **Option D:** This might also represent a valid route, making it incorrect as the exception.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the **portal system** primarily serves the anterior pituitary, allowing for the regulation of anterior pituitary hormones by hypothalamic releasing and inhibiting hormones. The neurohypophysis, being directly innervated by hypothalamic neurons, does not require this portal system for its functional regulation.

## **Correct Answer:** . Portal system