Espiral AtlasSinus of frontal bone
sinus frontalis
Study entry
Location
Between the outer and inner tables of the frontal bone, behind the superciliary arches and the root of the nose.
Structure
They are usually detected in children at about 7 years. Each sinus drains through a frontonasal duct into the ethmoidal infundibulum, which opens at the semilunar hiatus of the middle nasal meatus. They rarely have the same size; the septum that divides them is not always in the median plane. They vary from about 5 mm to large spaces that reach the greater wings of the sphenoid; often a sinus has a vertical part (in the squama) and a horizontal one (in the orbital part). When the supra-orbital part is large, its roof forms the floor of the anterior fossa and its floor, the roof of the orbit.
Innervation
Branches of the supra-orbital nerves (CN V1).
Source: cap. 8, «Senos paranasales»
Clinical correlation
Sinusitis
The paranasal sinuses continue with the nasal cavities through openings. Infection can pass from the nasal cavity and inflame and swell the mucosa of the sinuses (sinusitis), with local pain. Sometimes several sinuses become inflamed (pansinusitis). Edema of the mucosa can block one or more openings to the nasal cavity.
Infection of the maxillary sinus and transillumination
The maxillary sinuses are the ones most often infected, probably because the ostia are small and high on the superomedial walls. With a congested mucosa they become obstructed. With the head upright the sinus only drains when it is full, and lying on the side only the upper sinus drains. Transillumination, in a dark room, uses a strong light on the palate or cheek and produces a half-moon glow below the orbit. Excess fluid, a mass or thickened mucosa diminish the glow. For the frontal sinus the light is directed upward, under the medial part of the eyebrow, and the pattern varies greatly among people.
Related clinical cases
- Sinusitis
- Infection of the maxillary sinus and transillumination