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The nose (olfactory organ) is the organ of smell. It consists of groups of chemo receptors found in the epithelial lining of the upper portion of the nasal cavity. They are primary sense cells which form fine processes that extend into the surface film of mucus over the epithelium. Chemicals in the surrounding air dissolve in the mucus film and stimulate the chemo-receptors which send off sensory impulse through the olfactory nerves to the brain.

The sense of smell in dogs is acute. This makes dogs very efficient hunters so they can track and catch their prey easily and also sense the presence of predators and escape quickly.

In other organisms chemo-receptors may occur in other parts of the body for example the butterfly has chemo-receptors on its antennae for sensing its environment.

The Nose



  1. Enumerate four groups of sensory receptors stating their functions.
  2. Discuss briefly the sense of smell in mammals.

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