Frontal sinus

The frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges. Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle nasal meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the semilunar hiatus in the middle meatus.

Each frontal sinus is situated between the external and internal plates of the frontal bone. Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.

Each frontal sinus extends into the squamous part of the frontal bone superiorly, and into the orbital part of frontal bone posteriorly to come to occupy the medial part of the roof of the orbit.

Each sinus drains through an opening in its inferomedial part into the frontonasal duct.

The mucous membrane of the frontal sinus receives arterial supply from the supraorbital artery, and anterior ethmoidal artery.

Venous drainage is provided by the superior ophthalmic vein.

Lymph is drained into the submandibular lymph nodes.

The mucous membrane of the sinus is innervated by the supraorbital nerve, which contains the postganglionic parasympathetic nerve fibers for mucous secretion from the ophthalmic nerve.