Odor is a temperamental chemical compound that humans and other living organisms perceive via the sense of smell. Body odor easily comes to mind whenever an issue of smell is mentioned. It is a misconception to say that sweat causes body odor. Do you know why? Odor is a by-product of bacteria breaking down proteins in the human sweat. That means odor is not caused by sweat but bacteria in the sweat. If that is the case what about an unpleasant smell? How do deodorants work? And why do people smell differently from others?
So many questions to understand but as to why some people smell differently than others; The body can stimulate odors in the mouth and other holes in the body as well as bodily fluids due to the food we eat, age, genetics. Hygiene also plays a role.
However, this article focuses on odors originating from the chemical compounds bacteria exude in the cozy moist environment in the body and outside the body.
Odors are produced by molecules called Aroma compounds. These compounds are very small with a molecular weight of less than 300 atomic mass units (AMU).
The Atomic mass unit is a unit of mass for conveying masses of atoms, molecules, or nuclear particles equal to one twelve the mass of a single atom of the many carbon isotope present in a substance
Aroma substances are volatile compounds that are recognized by the odor receptor sites of the smell organ which is the olfactory tissue of the nasal cavity. Before we delve into aromatic compounds, let look at the olfactory system.
The olfactory system is a bodily organ that serve the sense of smell. The system consists of the nose and the nasal cavities which aid the upper part in the olfactory mucous membrane for the awareness of smell and the lower parts act as respiratory passages.
The organs of smell are invisible inside the nose. The walls of the nasal cavity are lined with millions of smell detectors. These olfactory receptors are nerve cells that emit a neutral message that is carried by the skull to the olfactory bulb- a nerve structure that transmits the information to the cerebrum.
The conscious representation of detected smell is produced in sectors deep within the brain. Since some of these sectors are also active in memory, a single smell may instantaneously prompt a past event.
Aromatic compounds are those that consist of a cyclic molecules. Most resemble benzene in structure. While many aromatic compounds do have an aroma, the word "aromatic" refers to a specific class of organic compounds in chemistry, not to molecules with scents.
Technically, aroma compounds include volatile inorganic compounds with low molecular weights that can bind olfactory receptors. For example, hydrogen sulfide (H2S) is an inorganic compound that has a distinctive rotten egg scent. Elemental chlorine gas (Cl2) has an acrid smell. Ammonia (NH3) is another inorganic odorant.
Odors are detected through two pathways. The first is the orthonasal pathway which involves odors that are breathed in through the nose. The second is the retronasal pathway that connects the top of the throat to the nasal cavity. In the orthonasal pathway, odors enter the nasal passages and are detected by chemical receptors in the nose.
The retronasal pathway involves aromas that are contained within the foods we eat. As food is being munched, Odors are released to travel through the retronasal pathway connecting the throat to the nasal cavity. Once in the nasal cavity, the chemicals are discovered by olfactory receptor cells in the nose. However, if the retronasal pathway is blocked, the aromas in foods we consume cannot reach odor detecting cells in the nose. This often occurs when a person has a sinus infection or cold.
Odors fall into several categories, including esters, terpenes, amines, aromatics, aldehydes, alcohols, thiols, ketones, and lactones. Here is a list of some important aroma compounds and their odors.
Indole and skatole
Blood and metallic
Strawberry or fruity scent
Banana and pear scent
Since we know Odors are stems from organic compounds. Let look at how body odors are generated.
Body odor is the unpleasant smell of a person. The human body generates smells called odorants. Small quantities of these odorants are important for bodily functions which don't lead to unpleasant odor. But, the accumulation of these compounds on the skin concerning time can result in an obvious smell. However, body odor becomes more distinct during puberty. This is because hormones and sweat glands become more active at this time. Also, people with certain medical situations like diabetes are more prone to body odor.
The root of odor as explained earlier is the breakdown of chemical compounds in munched food and other substances in the body by bacterias. But, natal sex, some therapies, and body treatment helps formulate unusual body odor profiles that can be identified by another person.
Most importantly, every individual skin contains two sweat glands called Eccrine and Apocrine.
Apocrine glands function at puberty and are linked with hairs in the underarms. These glands produce a thick, protein-rich sweat that is odorless. But, whenever bacteria break down the proteins, they produce odorant molecules in greater concentrations, causing body odor. In another hand, the eccrine gland is not linked with body odor.
Lastly, let see how the sense of smell affects our emotions.
The connection between our sense of smell and emotions is unlike that of the other senses because the olfactory nerves connect directly to the brain structures of the limbic system. Odors can trigger both positive and negative emotions as aromas are associated with specific memories.
Additionally, the emotional expressions of others can influence our olfactory sense. This is due to the recreation of an area of the brain known as the piriform cortex which is activated before odor sensation.
In conclusion, The piriform cortex processes visual information and creates a desire that a particular fragrance will smell pleasant or unpleasant.
Therefore, when we see a person with an unhappy facial mood before sensing an odor, there is an expectation that the odor is unpleasant. This expectation affects how we perceive the odor.
1."Body odor: Causes, prevention, and treatments" Retrieved from https://www.medicalnewstoday.com/articles/173478#what-is-it
2."Olfactory System - Sense of Smell" retrieved from https://googleweblight.com/sp?hl=en-US&geid=NSTN&u=https://www.thoughtco.com/olfactory-system-4066176
3. "Aroma Compounds and Their Odors" Retrieved from https://googleweblight.com/sp?hl=en-US&geid=NSTN&u=https://www.thoughtco.com/aroma-compounds-4142268
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