MODEL RELEASED. Smell. Composite image of a woman smelling a red rose, with images of scent mole- cules between her nose & the flower. A person's smell receptors lie in a small patch of mucous membrane in the lining of the roof of the nose. These are linked to the brain through the olfact- ory nerve. The mechanism of smell is thought to rely mostly on the vibration of the scent molecule as it strikes a smell receptor after dissolving in the mucus. This means that scent molecules with similar shapes may smell very different. The system is highly sensitive, with as few as four molecules being needed to produce a recognisable smell.