Sinus anatomy made simple

The paranasal sinuses of mammals form complex air-filled structures, and probably exist for a variety of functions including, but not exhaustively: protection of internal cranial structures, maintaining structural strength without a significant increase in weight, augmenting vocalisation, and to increase the intranasal cross-sectional area to aid particulate filtration and humidification of inhaled air. Unfortunately, their complexity also leads to disagreement among authors regarding the nomenclature as well as the degree of intercommunication present; however, the more common pathological processes are largely confined to the more easily defined (and larger) of the sinuses so in the majority of cases semantics are moot. It does, however, lead to discrepancies in the number of sinuses that are recognised, a fact compounded by some anatomic features unique to equids ...