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How do mucus and saliva help chemicals reach taste and smell receptors?

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A pine grosbeak with pink and gray plumage perches on a branch, eating red berries among autumn foliage. — Chemoreception Animals, such as this pine grosbeak, use chemoreception to respond to chemicals that can be tasted and smelled in their environments. Many of these chemicals affect behaviors such as food preference and defense.

Mucus and saliva are essential for chemoreception because they act as solvents, allowing chemical substances to reach and stimulate sensory receptors.

The Role of Saliva in Taste

For taste buds to be stimulated, substances must be in solution. Saliva serves as the necessary solvent for food materials, dissolving them so they can interact with the receptors. Additionally, saliva contains soluble proteins that may assist in transporting chemical compounds to these receptors.12

The Role of Mucus in Smell

In the olfactory system, the sensory nerve endings are covered by a thin layer of moisture, or mucus. This fluid dissolves microscopic particles carried by the air, enabling these chemicals to chemically stimulate the olfactory nerve cells.3

While water-soluble compounds can move freely through this mucus, many volatile and bitter-tasting compounds are not water-soluble. These substances are thought to be made soluble by binding to specific soluble proteins present in the mucus, which then transport them to the receptor cells. Once the stimulus is processed, odorant-degrading enzymes within the mucus help remove the molecules to prevent continuous, irrelevant stimulation of the receptors.2