Each frontal sinus drains onto the lateral wall of the middle meatus via the frontonasal duct, which penetrates the ethmoidal labyrinth and continues as the ethmoidal infundibulum at the front end of the semilunar hiatus.
The frontal sinuses are innervated by branches of the supra-orbital nerve from the ophthalmic nerve [V1]. Their blood supply is from branches of the anterior ethmoidal arteries.
The ethmoidal cells on each side fill the ethmoidal labyrinth (Fig. 8.235A,B). Each cluster of cells is separated from the orbit by the thin orbital plate of the ethmoidal labyrinth, and from the nasal cavity by the medial wall of the ethmoidal labyrinth.
The ethmoidal cells are formed by a variable number of individual air chambers, which are divided into anterior, middle, and posterior ethmoidal cells based on the location of their apertures on the lateral wall of the nasal cavity:
The anterior ethmoidal cells open into the ethmoidal infundibulum or the frontonasal duct.
The middle ethmoidal cells open onto the ethmoidal bulla, or onto the lateral wall just above this structure.
The posterior ethmoidal cells open onto the lateral wall of the superior nasal meatus.
Because the ethmoidal cells often erode into bones beyond the boundaries of the ethmoidal labyrinth, their walls may be completed by the frontal, maxillary, lacrimal, sphenoid, and palatine bones.
The ethmoidal cells are innervated by: the anterior and posterior ethmoidal branches of the nasociliary nerve from the ophthalmic nerve [V1], and the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion.
The ethmoidal cells receive their blood supply through branches of the anterior and posterior ethmoidal arteries.
The maxillary sinuses, one on each side, are the largest of the paranasal sinuses and completely fill the bodies of the maxillae (Fig. 8.235A,B). Each is pyramidal in shape with the apex directed laterally and the base deep to the lateral wall of the adjacent nasal cavity. The medial wall or base of the maxillary sinus is formed by the maxilla, and by parts of the inferior concha and palatine bone that overlie the maxillary hiatus.
The opening of the maxillary sinus is near the top of the base, in the center of the semilunar hiatus, which grooves the lateral wall of the middle nasal meatus.
Relationships of the maxillary sinus are as follows:
The superolateral surface (roof) is related above to the orbit.
The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face.
The posterior wall is related behind to the infratemporal fossa.
The maxillary sinuses are innervated by infra-orbital and alveolar branches of the maxillary nerve [V2], and receive their blood through branches from the infra-orbital and superior alveolar branches of the maxillary arteries.
The sphenoidal sinuses, one on either side within the body of the sphenoid, open into the roof of the nasal cavity via apertures on the posterior wall of the spheno-ethmoidal recess (Fig. 8.235C,D). The apertures are high on the anterior walls of the sphenoid sinuses.
The sphenoidal sinuses are related: above to the cranial cavity, particularly to the pituitary gland and to the optic chiasm, laterally, to the cranial cavity, particularly to the cavernous sinuses, and below and in front, to the nasal cavities.