As scent plays an important role in the behaviour of domestic cats you would expect their sense of smell to be excellent and it is.
The size of the tissue inside the nasal cavity which is involved with smell is up to ten times larger in area than that of humans at 20 square centimetres compared to 2-4 square centimetres for humans.
As for scent receptors (olfactory cells) the cat has 40 times the number compared to humans at 200 million compared to 5 million. Dogs have around 220 million.
All cat owners are familiar with their cat’s desire to sniff anything new. The sniff is a ‘disruption of the normal breathing pattern’. It allows the scent particles (molecules) to remain in the nasal passages for longer. Air is forced into a space above the subethmoidal shelf which traps the air allowing it to be in contact with the olfactory cells for longer.
In addition we also know about the famous Flehmen response. This describes the cat’s distinctive facial posture, mouth slightly ajar, head slightly up and body still, when inhaling air containing odours into the nasopalatine canals. These connect the mouth and nasal cavities to Jacob’s organ (vomeronasal organ), which is in the roof of the mouth and is comprised of a pair of fluid filled sacs.
Jacobs’s organ contains receptor cells. These connect to nerves. The nerves lead to the amygdala region of the hypothalamus of the brain. This region of the brain is concerned with social, sexual and feeding behaviours.
The cat’s sense of smell is awesome and superior to ours.
Note: the quote is from The Cat Its Behavior, Nutrition & Health by Linda Case