Anatomy and Physiology of Mastication and Deglutition

Esophageal Stage

(Purely reflexive, not under voluntary control!) 1. begins when bolus reaches orifice of the esophagus 2. bolus moves through the esophagus to the LES (lower esophageal sphincter) via peristaltic (wavelike) contractions and gravity *takes 10-20 seconds* 3. when the bolus enters the UES for transit to stomach... 4. the cricopharyngeus will again contract 5. larynx and soft palate will be depressed 6. respiration begins again 7. in normal swallow, respiration is suspended for 1 second

____ muscles plus the _____ ___ ______ ______ ____ _________ ____ are involved in the process

1. *55* 2. *the cranial and spinal nerves that innervate them*

Reflexes involved with swallowing

1. *chewing reflex* - Alternating L and R contraction of muscles of mandibular elevation and alternating with depression of the mandible 2. *rooting and sucking reflexes* - involves tactile stimulation of the perioral region (RR: rub the infant's cheek and he/she will turn toward the stimulus with mouth open. SR: initiated by light contact w/i the inner margin of the lips [which involves generating a labial seal via contraction of the obicularis oris and alternating tongue protrusion and retraction])

*THE FOUR STAGES OF SWALLOWING:*

1. *oral preparatory stage* - food is prepared for the swallow 2. *oral stage* - involves oral transit (propulsion) of the bolus to the esophagus 3. *pharyngeal stage* - involves transit of the bolus to the esophagus (involves physiological protective responses) 4. *esophageal stage* - food is transported from the upper esophageal region to the stomach

Pharyngeal Stage (new sequence)

1. as bolus reaches the faucial pillars, the pharyngeal swallow response begins w/ elevation of the soft *now the oropharynx is separated from the nasopharynx* 2. respiration ceases reflexively 3. *velum elevated, tongue retracted, lips sealed* 4. oral and nasal outlets closed (so air cannot escape or enter) 5. *food is entering the pharynx and the airway must be protected!* 6. *the vocal folds tightly adduct* 7. *with the airway sealed, the larynx moves up and forward as a unit* (UES relaxes) 8. food is propelled down the pharynx toward the esophagus by means of contractions of the superior, middle, and inferior pharyngeal constrictors (*takes one second!*)

Oral Stage

1. bolus of food is finally ready to swallow (new sequence) 2. tongue base is elevated in the posterior during mastication 3. now it drops down and pulls posteriorly 4. mastication stops 5. anterior tongue elevates to the hard palate and 6. squeezes the bolus back toward the faucial pillars 7. contact w/ the fauces, soft palate, or posterior tongue base appears to the be stimulus that triggers the reflexes of the pharyngeal stage *(takes one second!)*

Oral Preparatory Stage

1. food is prepared for swallowing - begins outside of the mouth with all of the senses in play (we decide HOW to eat/drink it) 2. put food in mouth 3. keep in mouth by occluding lips 4. lip seal demands we breathe from nose, so tongue bunches up in back and soft palate is pulled down to keep food in the oral cavity 5. tongue *cups* in preparation for food 6. food is ground up by coordinated activity of mastication/lingual muscles 7. tongue keeps food in oral cavity (seals along alveolar ridge) 8. as tongue holds food in place, it may compress it against the hard palate (partially crushing it in preparation for teeth) 9. tongue moves food onto grinding surfaces of teeth (pulling food back into oral cavity to be mixed with saliva) 10. tongue moves it back to the teeth for more chewing 11. salivary glands (parotid, submandibular, sublingual) secrete saliva into oral cavity to help form *bolus* 12. facial muscles of the buccal wall (risorius and buccinators) contract to keep from entering the lateral sulcus (b/w gums and cheek wall)

mastication and deglutition require:

1. integration of lingual, velar, pharyngeal and facial muscle movement 2. laryngeal adjustments 3. respiratory control

Contrast between infant and adult oral structure (pp. 407)

1. larynx elevated 2. hyoid elevated 3. no teeth 4. tongue fills the oral cavity 5. larger velum and elevated larynx play vital role in respiration and deglutition (infant *thrusts tongue* which triggers the swallow [look at diagram])

it includes...

1. moving unchewed food onto the grinding surface of teeth 2. chewing it 3. mixing it with saliva in preparation for swallowing

during mastication and deglutition, *all muscles inserting into the obicularis oris may participate in*

1. opening 2. closing 3. pursing 4. retracting the lips as food is received

5 basic tastes:

1. sweet 2. salty 3. sour 4. bitter 5. umami (MSG - meaty or protein-like)

More reflexes involved with swallowing:

3. *uvular or palatal reflex* 4. *gag (pharyngeal) reflex* - triggered by tactile stimulation of the faucial pillars, posterior pharyngeal wall or posterior tongue near the lingual tonsils 5. *retch and vomit reflex* - R: involuntary attempt at vomiting (ex. noxious smells) V: oral expulsion of gastrointestinal contents 6. *cough reflex* - dislodges something in the airway and is usually triggered by noxious stimulation of the pharynx, larynx, or bronchial passageway 7. *tongue base retraction and elevation* - may be stimulated reflexively by pulling the tongue forward 8. *pain reflex* - secondary to a sore in the mouth which can lead to problems with chewing and/or swallowing 9. *respiration reflexes*

Are taste receptors restricted to zones of the tongue?

Nope! We used to think that, but nope!

What is the Cricopharyngeus called?

The UES (Upper Esophageal Sphincter). Relaxing this sphincter gives the food a place to go!

Mastication

The process of preparing food for swallowing

tastes can, in REALITY, be sensed...

all over the tongue! (umami at the tip)

Sensation

associated with Mastication and Deglutition

taste receptors (taste buds) consist of...

chemoreceptors (respond to chemicals)

pharyngeal constrictors...

contract to move the bolus down the pharynx and into the esophagus

if your nose is plugged...

food tastes flat. Olfaction (smell) plays a vital role in appetite and taste

olfactory sensors are where?

in the epithileal lining of the upper posterior nasal cavity

Also,

laryngeal elevation

Is salivation response motor or sensory response?

motor response!

Perioral

mouth region

intrinsic and extrinsic tongues muscles are involved in...

moving food into position for chewing and preparation of the bolus for swallowing

Salivation

production and release of saliva into the oral cavity - is an important part of taste, mastication, and deglutition

Bolus

refers to a "ball" of food or drink

CSS

refers to chewing, sucking, swallowing

where is saliva produced?

salivary glands: *parotid, submandibular, and sublingual glands*

velar elevators...

seal off the nasal cavity to prevent nasal regurgitation

Olfaction

sense of smell

Gustation

sense of taste

Tactile

sense of touch mediated by *mechanoreceptors* (sensitive to physical contact)

taste drives...

the desire to continue eating (which fulfills nutritional requirements)

Deglutition

the process of swallowing

Peristalsis

wavelike action