Largest of paranasal sinuses
Occupy most of body of maxillae
Ethmoidal sinuses
Several in number
Not well developed until after age 2
Sphenoidal sinuses
Derive from extensions of ethmoidal sinuses into sphenoid bone around 2 years of age
Numbers different on either side
Bony septum between two sides
Only a thin plate of bone separates them from critical structures in the anterior and middle cranial fossae: optic nerves, pituitary
gland, internal carotid arteries, cavernous sinuses
[Plate 46, Orientation of Nerves and Vessels of the Cranial Base]