Sinus of frontal bone

Frontal sinuses, also known as sinuses of frontal bone, are a pair of air-filled cavities–the paranasal air sinuses–located within the frontal bone, deep to the superciliary arches. Each sinus extends up, back, and to the side. Above, they stretch above the medial end of the eyebrow, and towards the back, they extend into the inner part of the orbit’s roof. The two frontal air sinuses are divided by a thin bony septum, which often leans to one side, making the sinuses different sizes. Their size varies among individuals and are generally larger in men than in women. These sinuses are lined with a mucous membrane and has a passage, known as the frontonasal duct, that connects to the nasal cavity and opens into middle meatus within the semilunar hiatus at the front.

Frontal sinuses fully develop around the age of 7-8, but they don’t reach their full size until puberty. They receive blood supply from the supraorbital vessels and the superior ophthalmic vein, and are innervated by the supraorbital nerve.