## **Core Concept**
The middle meatus is a passage in the nasal cavity that receives drainage from several paranasal sinuses and the anterior ethmoidal cells. The **middle meatus** is part of the **osteomeatal complex**, which plays a critical role in the drainage and ventilation of the frontal (anterior), anterior ethmoid, and maxillary sinuses.

## **Why the Correct Answer is Right**
The correct answer, , drains into the **sphenoethmoidal recess**, which is located above and posterior to the superior turbinate. This recess is associated with the drainage of the **sphenoid sinus**. The other options drain into the middle meatus: the frontal sinus, anterior ethmoid cells, and the maxillary sinus all drain through the osteomeatal complex into the middle meatus.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The frontal sinus drains into the middle meatus via the frontonasal duct, which opens into the anterior part of the middle meatus.
* **Option B:** The maxillary sinus drains into the middle meatus through the semilunar hiatus.
* **Option C:** The anterior ethmoidal cells also drain into the middle meatus.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **osteomeatal complex** is crucial for the drainage of the frontal, maxillary, and anterior ethmoid sinuses. Blockage of this area can lead to sinusitis involving these sinuses.

## **Correct Answer: D. Sphenoid sinus**