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What is Paranasal sinuses present at birth are and explain in detail?
Paranasal sinuses develop as outpouchings from the mucous membrane of a lateral wall of the nose. 
The growth of sinuses continues during childhood and into early adult life.
Radiologically maxillary sinuses can be identified at 4-5 months, ethmoids at 1 year,  sphenoid at 4 years and frontals at 6 years.