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olfactory nerves The nerves of smell and the first of the 12 paired CRANIAL NERVES arising directly from the brain. The olfactory nerves lie on the floor of the front section of the cranial cavity and run forward, close together, over the roof of the nose. From their terminal bulbs many tiny, hair-like filaments pass down through perforated bony plates (cribriform plates) into the upper part of the nose. Tiny particles of odorous material dissolved in the nasal secretions can be detected by the olfactory nerve endings with great sensitivity and discrimination.