Physiology of Mastication and DeglutitionChapter 8Perry C. Hanavan, Au.D.

Mastication & DeglutitionMastication:Processes involved in food preparation, including moving unchewed food onto the grinding surface of the teeth, chewing, it, and mixing it with saliva in preparation for swallowingDeglutition:swallowing

Stages of Deglutition

Stages of Duglutition

DeglutitionDisphagia Dr. Steven Feinberg Discusses Swallowing DisordersNormal Deglutition (PPT)VideofluoscopyXray

Rooting & SuckingRoot ReflexResponse of infant to tactile stimulation of the cheek or lips; causes infant to turn toward the stimulus and open mouthSuck ReflexInvolves tongue protrusion and retraction in preparation for receipt of liquid; stimulated by contact to the upper lip

Root & Suck Reflex

Other ReflexesBabinskiSteppingStartle reflexPalmar/grasp reflexDive Reflex

Adult vs. Child

Infant vs. Adult

Videoflouroscopy

Stages of Duglutition

Lower Esophageal Sphincter

Herniation of Stomach

Developmental MalformationsNormal esophagusEsophagus anatomising with tracheaEsophagus stenosisEsophageal discontinuity with tracheal portingEsophageal fusing with trachea

Developmental Malformations

GERDGastroEsophageal Reflux DiseaseStomach contents/acids recycled in esophagus (causing heartburn) and pharynx and perhaps can be aspiratedAdditional links on GERDLapSurgAmerican Family PhysicianThe Purple PillReflux EsophagitisReflux Laryngitis

Innervations of Tongue

Salivation Glands & Ducts

Gustation and Olfaction

Gustation and OlfactionHave you ever wondered why food loses its flavor when you have a cold? It's not your taste buds' fault. Blame your stuffed-up nose. Seventy to seventy-five percent of what we perceive as taste actually comes from our sense of smell. Taste buds allow us to perceive only bitter, salty, sweet, sour and savoury flavors. It's the odor molecules from food that give us most of our taste sensation.

TasteTaste drives appetite and protects us from poisons.We like the taste of sugar because we have an absolute requirement for carbohydrates (sugars etc.). We get cravings for salt because we must have sodium chloride in our diet. Bitter and sour cause aversive, avoidance reactions because most poisons are bitter (most bitter substances are bad for you - certainly in excess) and off food goes sour (acidic). We have a need for protein--amino acids are the building blocks for proteins, so the "new" taste quality umami (pronounced: oo-marmi) which is the meaty, savoury taste drives our appetite for amino acids. This taste has been known to the Japanese for a long time - but has only recently been recognized by the West. Bacon really hits our umami receptors because it is a rich source of amino acids.

TasteIn mammals, taste buds are aggregations of 30-100 individual elongated "neuroepithelial" cells (50-60 microns in height, 30-70 microns in width), which are often embedded in specializations of surrounding epithelium, termed papillae. At the apex of the taste bud, microvillar processes protrude through a small opening, the taste pore, into the oral milieu. Just below the taste bud apex, taste cells are joined by tight junctional complexes.

Taste PapillaeTaste papillae can be seen on the tongue as little red dots, or raised bumps, particularly at the front of the tongue. These are actually called "fungiform" papillae, because they look like little button mushrooms. There are three other kinds of papillae, foliate, circumvallate and the non-gustatory filiform. Taste buds, on the other hand, are collections of cells on these papillae.

Taste Sensors

Taste

Neurology of Taste

Routing of Taste

OlfactionTo identify the smell of a rose, the brain analyzes over 300 odor molecules. The average person can discriminate between 4,000 to 10,000 different odor molecules. We inhale airborne molecules that travel to and combine with receptors in nasal cells. The cilia, hairlike receptors that extend from cells inside the nose, are covered with a thin, clear mucus that dissolves odor molecules not already in vapor form. When the mucus becomes too thick, it can no longer dissolve the molecules.

Olfaction

Olfaction

Olfactory Bulb

Mechanoreceptors

MechanoreceptorsRespond to being mechanically pushed and pulled through touch, pressure, gravity, stretch, and movement.As their contour changes, mechanoreceptors supply information to the animal about shape, texture, weight, and the landscape of objects in the external environment. Through the use of mechanoreceptors we can feel, maintain balance, and even hear.Feeling occurs when mechanoreceptors detect touch, pressure, and pain as objects come in contact with the skinTouch receptors are not distributed evenly over the body.The fingertips and tongue may have as many as 100 per cm2; the back of the hand fewer than 10 per cm2.

MechanoreceptorsOther kinds of mechanoreceptors:proprioception, or balance, which enables an animal to know the position of its body and are located within muscles, tendons, and jointsProprioception is our "body sense". It enables us to unconsciously monitor the position of our body. It depends on receptors in the muscles, tendons, and joints. If you have ever tried to walk after one of your legs has "gone to sleep", you will have some appreciation of how difficult coordinated muscular activity would be without proprioception.

Brainstem Functions

http://youtube.com/watch?v=e193uXOq7ZYhttp://youtube.com/watch?v=WavjbJhiRAEhttp://youtube.com/watch?v=FSHGucgnvLU http://youtube.com/watch?v=FSHGucgnvLU