Several air-filled cavities, known as sinuses, are situated in the skull bones around the nose and the eyes. The size and shape of these sinuses vary between individuals. Sinuses are not present at birth but gradually develop throughout childhood. They help to lighten the skull bones and give the voice resonance. Within the lining of the sinuses are many mucus-secreting glands. Mucus passes continuously through narrow channels that lead from the sinuses to the back of the nose. The mucus traps small airborne particles and moistens inhaled air as it passes though the airways.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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