Nose Detect Smell

How does the nose detect smell?

            The nose is an indispensable organ that is used for breathing and sense of smell. If it is not working properly, we cannot distinguish between foul smell and fragrance. How the nose detects smell?

The Internal Structure of Human Nose

            The nose may look like a very simple structure but it is very complicated in nature. The nose is composed of two bones and is situated between the yes below the head and above the lips. These two bones from a kind of bridge. In between them lies a wall of cartilage. Which divides the nose into two parts called the nasal cavities. At the end of the nasal cavities lies a thin membrane called the mucous membrane, which secretes a special fluid. This fluid keeps the nose moist. The hair inside the nose waves back and forth to prevent dust particles, bacteria and fluids from entering the lungs. So the air that goes into the lungs through the trachea has already been filtered by the nose.

            The smell is detected by the cells present in the two olfactory nerves situated at the end of the nasal cavities. These cells are called receptors and are embedded in the mucous membrane. They are spread over an area of 250 square millimeters.

            It is believed that the sense of smell is closely related to that of taste. We know that if a man has blindfolded and his nose was blocked, he would not be able to differentiate the taste between a potato and an apple?

How do the Fishes Smell Things?

            There are two pairs of nostrils in fish. Each nostril has two openings, which are called pits. One opening is in the front, and the other directly behind it. A small flap separates the two pits. However, the location of the nostrils may vary from species to species.

Fishes find their way back home by smelling

            When fish is under water, a current of water enters form the front pit and comes out through the rear one. As the water flows inside, it stimulates the sense cells, which enables the fish to catch the smell. Many fishes have a keen sense of smell. They can detect even the faintest smells.

            In fact, the sense of smell may help a fish to find its way home. Some fish could distinguish between the water of two creeks through smell. But if their noses are plugged, they get lost. To prove this fact some researchers had performed certain experiments. In one experiment, a large number of salmon fish were taken out of their home stream. Half of them had their noses plugged; the other half did not. The fishes with plugged noses got lost and the rest half could find their way back home again. Anglers use peculiar scented fish-food to attract them.

             Apart from the sense of smell, the fishes have other sensory perceptions also such as the sense of touch, taste hearing and sight.