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Gustatory system

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Gustatory system is the biological system of taste. Standing as one of the five senses of the body, the gustatory system is an essential attribution to our lives. Just as seeing and hearing is important, the ability to taste is also handy. God gave us food as a pleasurable gift for us to enjoy and the gustatory system helps make it possible for us to be able to taste may different foods and drinks. The taste cells we have are all over our mouth and especially on the tongue, receive taste information from substances dissolved in the saliva on the surface. These taste cells that transmit the information to nerve fibers, which bring the information to the brain. [1] The gustatory system is a very intricate and interesting process that is often times underappreciated.

Structure and Function

Main Article: Taste bud
Structure of the papilla foliata of a rabbit.
Structure of a taste bud.

The ability to taste is incredibly intricate. The taste buds on the papillae of the tongue are what makes it possible for us to taste the foods and drinks that we taste today. Taste buds are not only located on the papillae of the tongue but they're also found in the larynx, upper esophagus, palate, and pharynx.[2]Taste buds look like little pears and between 30-100 taste receptor cells reside within each taste bud on the tongue. Gustatory cells and supporting cells are the two types of cells within a taste bud. The shape the bud makes is evident because of the contribution of the supporting cells. Each taste bud has a hole at the surface called a taste pore and gustatory hairs sprout out of the taste pore to the surface of the tongue. [3]

There are four different papillae on your tongue. Foliate papillae are longer looking and are found on the sides of the tongue near the back. Fungiform papillae are smaller and found near the front. Circumvallate papillae are the largest of the papillae and they reside near the posterior side of the tongue. Filiform papillae is another type of papillae that is found all over the tongue but this type of papillae does not contain taste buds.[4]

Taste receptor cells are elongated and start at the bottom of the taste bud and extend to the surface of the tongue. Microvilli exist on one end of the cell and are vital within the realm of tasting. They bring in the liquefied substance so that the receptor cells can do their job. Nerve fibers, on the other end, then receive information that the microvilli brought in. The intensity of the taste of different substances depends on the number of taste buds in that particular area of the tongue.[2]Substances brought in by saliva attaches to the various taste cell membrane receptors present all over the tongue. Then the stimuli activate ion channels, which sends information to the brain by releasing neurotransmitters.[5]

Divisions of Taste

This is a diagram of the tongue showing it's different taste receptors.

The tongue senses different tastes stronger in some areas of the tongue compared to others. Bitter, salty, sour, and sweet are the four taste receptors we have. The bitter receptors reside in the very back of our tongue; sour taste receptors are found on the sides. [6]Bitter exists as one taste receptor out of four total. These taste receptors reside near the back of the tongue. Calcium and magnesium inorganic salts, along with organic compounds, stimulate the bitterness we taste.[6]

A small number of people are able to taste phenylthiocarbamide, which is an organic compound. This ability to taste this compound makes them more perceptive to bitterness. Acid reflux and vomiting stand as the most common reason for bitterness. With a bitter taste comes symptoms, such as a dry mouth, stinky breath, change in facial movements, and loss of apatite. [7]

Salt is one of the four taste receptors and are located towards the front of the tongue. These taste receptors let sodium ions right into the cell through ion channels. Aldosterone increases the ability to take in salt; this can be helpful for people who need more salt in their body. [8]G-protein-coupled receptors reside on the tops of the cells within the taste buds. Sweet matter attaches to these receptors, which triggers the adenylyl cyclase. This process soon closes the potassium channels.[8]


Disorders and Deficiencies

Each year, over 200,000 report to their doctor their lack of ability to taste or smell. That is just proof that taste disorders are not uncommon. Taste perception is known to be the most widespread taste disorder as of today. Taste perception is when someone has a random, long-lasting tang in his or her mouth. Ageusia is when a person cannot distinguish different tastes at all and hypogeusia is when one has a hard time tasting one of the different tastes. Dysegeusia is when a metallic, salty, or soiled taste resides inside the mouth. This is very uncomfortable especially with middle-aged woman because it usually comes a burning feeling.
The reasons for most taste disorders include:

  • Interaction with insecticides, antihistamines, antibiotics, and some medications
  • Injury to the head
  • Lack of mouth hygiene
  • Mid-ear or respiratory infectivity
  • Surgeries to the throat, nose, or ear
  • Radiation exposure near the neck and head

Once someone realizes that they have a taste disorder, a dotolaryngologist is usually the one to diagnose him or her. This kind of doctor is skilled at dealing with the throat, neck, head, nose and ear. The dotolaryngologist will usually test the patient’s tasting ability by determining his or her’s lowest level of taste recognition. Comparison between diverse tastes could also be tested. Today, a new method has been utilized. A “sip, spit, and rinse” test is common; when a patient takes a sip of a solution and then spits it out. Some may think that getting rid of these taste disorders is impossible, and some are, but a dotolaryngologist would advise him or her to go through the following procedures to help the ability to taste different substances.

  • Cooking with diverse consistencies and colors
  • Utilize spices and herbs instead of salt and sugar
  • Add nuts, cheese, olive oil, bacon or butter to the recipe
  • Try to stick to the simple foods, this way the chances of tasting a certain substance, with no interference, will be higher[9]

Video

A brief overview of the gustatory system.

References

  1. unknown The Gustatory System Sensory Processing Disorder. Web. Date-of-access: Feb. 27, 2013.
  2. 2.0 2.1 Hutchins, Max O. Chapter 9: Chemical Senses: Olfaction and Gustation Neuroscience Online. Web. Date-of-access: Feb. 20, 2013.
  3. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. 268. Print.
  4. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. 268. Print.
  5. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. 268. Print.
  6. 6.0 6.1 Author Unknown. Taste Buds Inner Body. Web. Date-of-access: Feb. 20, 2013.
  7. Williams, Robert. Bitter Taste in Mouth: Symptoms “Better Medicine”. Web. Date-of-access: Feb. 23, 2013.
  8. 8.0 8.1 unknown The Sense of Taste RCN D.C. Metro". Web. Date-of-access: Jan. 25, 2013.
  9. unknown Taste Disorders NIDCD. Web. Date-of-access: Jan. 26, 2013.