What is "ethmoidal sinus"?

The ethmoidal sinus is a complex network of small, interconnected air-filled spaces located in the ethmoid bone of the skull. It is divided into multiple compartments, each lined with mucous membranes. The ethmoidal sinus helps to lighten the weight of the skull and acts as a pathway for air circulation and mucus drainage. It also plays a role in the sense of smell, as the olfactory nerve fibers pass through the ethmoid bone to reach the nasal cavity.