Earth Science: Humans – Nose and Tongue
The senses of smell and taste are closely related to each other. This becomes obvious when a person has a cold; even the tastiest food seems bland due to an otherwise healthy, but now diminished sense of smell.
The olfactory epithelium inside the superior nasal concha is responsible for taking in smells. It consists of palisade-like sup- porting cells and threadlike olfactory cells in between.
These turn into nerve fibers at the base of the epithelium. On top of the olfactory cells there are small cilia that act as receptors for gaseous fragrance com- pounds and generate a nervous impulse that is transmitted, via the olfactory bulb, to the appropriate area of the brain.
The outside layer of the olfactory epithelium is covered by a thin film of liquid produced by specialized mucous glands, which are located between the sup- porting and olfactory cells. This mucous layer prevents the cells that are constantly exposed to air flow from drying out.
The olfactory epithelium is, however, located slightly off the main stream of breathing air so that we begin sniffing as soon as we cannot clearly identify a certain scent. This narrows the lower part of the nose and the intermittent breathing draws in more air closer to the olfactory tissue located inside the nasal cavity.
Sense of taste
One of the most important aspects of taste is the ability to differentiate edible from inedible or poisonous substances. This is possible through numerous taste buds, which are situated on the edges of small buds called papillae. They are predominantly located on the mucous membranes of the tongue and partly on those of the mouth.
These taste buds contain receptor cells that are surrounded by supporting cells. Nerve fibers attach to the bottom of the receptor cells and transmit impulses of taste to the brain. The taste buds also contain basal cells which are responsible for the continuous reformation of new receptor cells.
This is necessary due to their short life span of only about ten days. Despite having several thousands taste buds, we can only differentiate between four basic tastes: sour, sweet, salty, and bitter.
BITTER AFTERTASTE
Taking in certain bitter substances, such as medicine, results in the familiar bitter aftertaste on the tongue. This is due to a delay in the flavor getting washed out of the dents lining the papillae where the taste buds are located.
This is done by salivary glands at the base of the papillae, which are constantly producing saliva to remove all the old flavors and clear the taste buds for new impulses.
BASICS
BODY ODOR is as unique as a fingerprint. Personal scent—the result of sweat, body fluids, and broken down protein—may play an important part in how much we like or dislike another person’s “smell.”