The Sense of Smell
In Part 17 of this series, we looked at the first of the five senses, the sense of taste. This week we will take a look at the sense of smell, also known as olfaction.
Whether you realize it or not, the air we breathe is full of millions of molecules that float and drift along. Among those is oxygen, O2, which we breathe in to use in our bodies and then we exhale, releasing carbon dioxide, CO2, back into the air. An unstable form of oxygen is known as ozone, O3. Did you know that you can smell ozone in the air? Think back on the last time there was a thunderstorm with lightning in your area. Could you smell what most people call the smell of rain? A large part of that odor was ozone. When lightning occurs, it causes stable oxygen to convert into unstable ozone and it is this ozone that gives you that smell of rain.
Our noses can detect thousands of different odors, but according to some sources, there are only seven basic odors and the all rest are combinations and variants of these basic seven. The seven basic odors are: acrid, camphor, ether, flower, mint, musk, and putrid.
Structures involved in the sense of smell are:
I. Nose – The nose plays an important role in respiration and the sense of smell. The main features of the nose consist of the ethmoid bone, nasal septum and nostrils. In the upper roof of the nostrils is an area where the sense of smell takes place.
A. Olfactory Epithelium – In the human nostrils there is a patch of epithelium cells responsible for detecting smells. The olfactory epithelium cells are covered by a mucous. This mucous traps molecules that are in the air as you breathe in. These molecules are then transported through the mucous to the olfactory receptor neurons that line the olfactory epithelium.
1. Olfactory Receptor Neurons – It is estimated that the human nose contains about 5-6 million receptor neurons compared the 200+million in dogs. Each receptor neuron has cilia that reach out into the mucous lining. These cilia are lined with olfactory receptors which detect the various molecules the mucous has picked up. The olfactory receptors then send their signals through the olfactory nerves to the brain where they are interpreted in the olfactory bulb which is located in the orbitofrontal cortex.
The sense of smell is closely associated with the sense of taste. Quite often the same molecules and chemicals that stimulate the taste buds also stimulate the olfactory receptor neurons, allowing the individual to taste and smell the same item.
Unlike taste, smell is something that we usually don’t take for granted. Taste generally has to be a physical contact with the tongue, while smell is open to anything in the air. When you drive past your favorite restaurant you can often smell their grill and what they’re cooking. And on the flip side, you can always tell when someone has hit a skunk on the road and you can smell it a half mile away.
People also give off specific chemical signals known as pheromones. Pheromones can be a powerful stimulus, especially to the opposite sex. An entire industry of perfumes and colognes worth billions of dollars is based upon our ability to detect certain types of pheromones with the goal of attracting the attention of someone special.
When you examine the molecular and chemical make up of smell, just like we did for taste, it becomes apparent that it’s not just a simple thing after all. It is a series of chemical and molecule capture, detection, reaction, signal and interpretation. Since most animals have a sense of smell, evolutionists believe it to be a product of common ancestry, something we have all inherited from the very first creature the evolved it.
But how did it first evolve. In order for the very first creature to be able to detect an odor, they would have needed to evolve some type of receptor neuron along with the proteins involved in the actual detection. They would also need to have evolved the right kind of nerves to carry the signals from the nasal area to the brain and they would have had to evolve the section in the brain that interprets the signals and register them as a smell. If any one piece of this chain of structures is missing, the sense of smell does not work. Evolution is based on passing down things that work, not things that don’t work. Therefore, all of these pieces would have been necessary to have evolved at the same time in order for it to be a successful trait to pass on to the next generation. The odds of that happening are virtually zero.
The only real explanation for the origin of the sense of smell is that God created animals and man with the sense of smell from the very beginning. We are also told that God is pleased with certain smells and aromas as we see in the same verses used last week:
It is a burnt offering to the LORD. It is a pleasing aroma, a food offering to the LORD. Exodus 29:18
Then you shall take them from their hands and burn them on the altar on top of the burnt offering, as a pleasing aroma before the LORD. It is a food offering to the LORD. Exodus 29:25
The other lamb you shall offer at twilight, and shall offer with it a grain offering and its drink offering, as in the morning, for a pleasing aroma, a food offering to the LORD. Exodus 29:41
Take a journey from conception to birth with Dr. David Menton, former professor of anatomy at the prestigious Washington University School of Medicine in St. Louis. Dr. Menton provides both a biblical and scientific answer to the question of when life begins.
Taken from one of Dr. Menton’s lectures, this video will reveal the wondrous design of the womb along with the numerous miracles involved along every step of the development of the unborn child.
Following the tragic starvation induced death of Terry Schiavo, Dr. Menton clearly shows the value and sanctity of human life.
With grace and sensitivity Dr. Menton concludes with a salvation message and explanation of the second birth process as described in John 3.