SINUS
Paranasal sinuses form developmentally through
excavation of bone by air-filled sacs (pneumatic diverticula) from the nasal
cavity. This process begins prenatally, and it continues through the course
of an organism's lifetime. The paranasal sinuses are joined to the nasal cavity
via small orifices called ostia. These become blocked relatively easily by
allergic inflammation, or by swelling in the nasal lining which occurs with
a cold. If this happens, normal drainage of mucus within the sinuses is disrupted,
and sinusitis may occur. These
conditions may be treated by drugs such as pseudoephedrine, which reduce moisture
in the sinuses, or by traditional techniques of nasal cleansing. Malignancies
of the paranasal sinuses comprise approximately 0.2% of all malignancies.
About 80% of these malignancies arise in the maxillary sinus. Tumors of the
sphenoid and frontal sinuses are extremely rare. (1)
source
(1) wikipedia