Marvels in the Scent-Perception System

Your senses provide you with enormous amounts of information about the outside world. We may not always be aware that our senses play a vitally important role in our perception of what's going on around us. When you close your eyes and smell dinner cooking in the kitchen, you can unfailingly identify what is on the menu. By scent alone, you can tell whether or not the dinner is cooked, or whether something in the refrigerator has spoiled. We can also identify a great many environments, such as hospitals, restaurants, markets, schools or our own homes, from their odors alone.

Your capacity to detect smells is much greater than you imagine. Some researchers even say that it would be a mistake to reduce this capacity to a numerical figure, since our sense of smell is able to distinguish between countless different odors. Let us now look more closely at the marvels of creation that make up this supremely competent and highly accomplished system.

The Unbelievable Motion in Mucus

Two olfactory regions (Regio olfactoria) are located in the roof of the two nasal cavities of the human nose, just below and between the eyes. (Figure 6) The region occupies 2.5 square centimeters (0.39 square inches) and is covered in mucus secretions. Mucus is a sticky fluid secreted by Bowman's glands. The mucus layer covering the olfactory region is about 0.06 millimeter (0.023 of an inch) thick. If this layer were even slightly thicker, your capacity to perceive smells would decline considerably. The reason why your ability to perceive smell decreases when you catch a cold is because mucus production is increased. If the thickness of the mucus were any less, then your body's immune system will be weakened and the olfactory micro-hairs in the mucus layers could easily be damaged.

The basic functions of mucus have been known for some time. Among other things, it prevents drying inside the nose and constitutes a defense against foreign chemical substances. But only recently was it realized that mucus has a most organized structure and constitutes a most ideal environment. Indeed, it is a very rich mixture of proteins, enzymes, mucopolysaccharides, immunoglobulins and lipids.

(Figure 6) The cellular organization of the olfactory region.

The first stage in olfactory perception begins in the mucus layer. In order for scent particles contact the receptors in the micro-hairs, they must first pass through this stratum. At this stage, special connection proteins in the mucus layer combine with scent particles and serve them literally as guides. These proteins are still the subject of research. They are thought to assist scent particles and receptors to come together and also prevent excessive numbers of scent molecules from reaching the receptors. What is certain is that the proteins recognize thousands of different scent particles, establish communication with them and regulate the molecular traffic in the mucus layer—reaffirming the fact of an astonishing creation.

Imagine yourself wandering in a garden filled with lovely-smelling flowers and holding them up to your nose to smell them, one by one. In order for new scent particles to reach the receptors in your nose, the old molecules need to be disposed of, or it will be impossible for you to detect the smell of the second flower after smelling the first. Such an eventuality could have unwelcome consequences, but it is prevented by certain enzymes within the mucus.

To describe it in simplified terms, after a specific—but quite brief—length of time, the enzymes in question alter the structures of the scent particles and convert them to a state where they no longer stimulate the receptors. Later, these neutralized molecules are sent to the stomach together with the mucus that traps them, and are thus eliminated. Note that it is not expert biochemical engineers and scientists who accomplish this, but enzymes with no mind or consciousness. In addition, the enzymes in the mucus achieve this by constantly making new "decisions." Naturally, enzymes cannot manage such complicated tasks all by themselves. All this takes place through the limitless knowledge and magnificent creation of God.

In conclusion, there is an astonishing activity in the depths of the mucus layer that manages the scent-perceiving region in your nose. Countless processes, of which you are unaware and cannot see with the naked eye, proceed with perfect planning and timing.