Equine Sinusitis
The word sinusitis commonly refers to the presence of inflammation or infection in one or more of the paranasal sinuses. The paranasal sinuses are air-filled structures that form part of the upper respiratory tract. Two double sets of sinuses, named the maxillary sinuses, facilitiate the placement of other structures such as upper molar teeth in a triangulated framework, thus providing great supportive rigidity without adding much weight to the horse's head. The sinuses communicate with the nasal passages which, in normal circumstances, allow fluids from the sinuses to drain into them.