What defines sinuses in the context of anatomy?

In the context of anatomy, sinuses are defined as air-filled cavities located within certain bones of the skull. These cavities are lined with mucous membranes, which help to humidify and filter the air we breathe, reduce the weight of the skull, and play a role in the resonance of our voice. Sinuses are not just random spaces; they have specific functions and contribute to the overall health of the nasal and respiratory systems.

While option A mentions fluid-filled sacs, this does not accurately describe the characteristic function of sinuses in anatomy, as sinuses specifically refer to air-filled areas rather than being primarily fluid-filled. Option B refers to mucosa-lined cavities but does not specify that these cavities must be filled with air and does not emphasize the anatomical location in relation to bones. Option D discusses fibrous tissues in the lungs, which is unrelated to the definition of sinuses and does not connect to the specific structural and functional attributes of sinuses in the skull.