Swallowing Disorders in Infants, Children, and Adults

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Swallowing Disorders in Infants, Children, and
Adults
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I. Neurophysiology of Swallowing

• Normal Aerodigestive Tract Anatomy

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Anatomical Orientation

• The evolution of human anatomy has produced a
  system in which the structures of speech,
  swallowing, and respiration are shared.
• The major systems involved in the aerodigestive
  tract include
• a. The Oral System
• b. The Pharyngeal System
• c. The Laryngeal System
• d. The Esophageal System
• e. The Respiratory System

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The Oral System

• The cheeks, hard and soft palates, lips, and
  tongue form the oral cavity, which aid in
  mechanical digestion.
• The vestibule is the space between the cheeks and
  lips and teeth and gums.
• The oral cavity proper extends from the vestibule
  to the fauces.
• The oral system is composed of both rigid and
  flexible tissues.
• Rigid elements include the teeth, mandible and
  maxilla, temporo-mandibular joint (TMJ), and hard
  palate.

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The Oral System

• In addition, the oral system contains multiple
  major and minor glands, other soft tissues
  including mucosa, and an elaborate array of
  vascular and nervous tissue.
• These components function to serve both nutritive
  and nonnutritive oral functions.
• All of these component parts must operate in
  harmony for function to be optimal.

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Maxillae and Mandible

• Whereas the maxilla is the stable member of the
  jaws, the mandible is the moveable part.
• The maxilla is fused to the skull and to move the
  maxilla one must move the entire head.
• Portions of the maxilla form the hard palate, and
  provide for a physical separation of the oral
  from the nasal cavities.
• The hard palate also serves as a surface against
  which the tongue pushes to propel the bolus into
  the pharynx in preparation for swallowing.

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Maxillae and Mandible

• On the other hand, the mandible attaches to the
  skull via the temporomandibular articulation and
  a sling of muscles.
• TMJ articulation is a complicated hinge and glide
  articulation.
• Mandibular movements involve the entire mandible
  and the points of the movement are the TMJs.
• As one side of the mandible moves, the opposite
  side must move accordingly.

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Maxillae and Mandible

• Mandibular movements, dictated and limited by the
  TMJs, the muscular sling, and the occlusion of
  the teeth, may be classified as masticatory and
  nonmasticatory.
• The masticatory movements are the ones necessary
  for the manipulation and chewing of foods,
  whereas the nonmasticatory movements entail all
  other normal and abnormal movements used in
  speech and oral-facial habits.

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Teeth

• Humans have two sets of dentition an initial
  deciduous, or primary set, which is unerupted yet
  well developed at birth and a secondary or
  permanent set, which are developing in the dental
  arch at the time of birth and while the deciduous
  teeth emerge.
• Clinical eruption of the primary teeth begins
  before the age of 12 months and continues until
  approximately 24 months.

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Teeth

• Shedding of the primary arch begins around age
  6-7 years and continues until the age of 11 or 12
  years, when the full complement of permanent
  teeth has erupted.
• The adult dental arch as 4 types of teeth, each
  type differs in appearance and reflects their
  divergent functions
• the incisors (4 central and 4 lateral)
• the canines (4)
• the bicuspids (8) and
• The molars (12).

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Teeth

• The diet of primitive humans necessitated a
  greater reliance on incisors and canines for
  cutting and tearing foodstuffs prior to
  ingestion.
• In the modern diet of highly processed foods,
  incisors and canines retain their utility for
  turkey legs, carrot sticks, lengths of thread,
  cookies, tortilla chips, etc.
• The human diet also requires significant amounts
  of grinding.
• The bicuspids and first molars perform the main
  portion of heavy grinding, and loss of these
  teeth severely impairs chewing ability.

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Muscles of Mastication

• As a group, the muscles of mastication are
  responsible for the actions of the mandible in
  chewing.
• They are all innervated by the Vth trigeminal
  cranial nerve.

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Temporalis Muscle

• The temporalis muscle is a large fan-shaped
  muscle originating from the temporal fossa of the
  skull.
• It inserts in the ramus and coronoid (anterior)
  process of the mandible.
• Its muscle fibers are long and parallel and
  assist in elevating the mandible and in
  maintaining the mandible in place during
  inactivity.

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Masseter Muscle

• The masseter muscle stretches in a rectangular
  plate from the zygomatic arch to the outer
  surface of the mandible ramus.
• It elevates the mandible for crushing and
  grinding movements of chewing and provides stable
  closure during the swallowing pattern.

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Internal Pterygoid Muscle

• The internal (medial) pterygoid muscle is a
  rectangular-shaped muscle found deep to the
  masseter muscle.
• It originates in the pterygoid fossa of the
  sphenoid bone and inserts in the ramus.
• It is a weaker counterpart to the masseter and
  helps elevate the mandible in unity with the
  masseter and the temporalis muscles.

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External Pterygoid Muscle

• The external (lateral) pterygoid muscle is a
  short, thick, pyramidal-shaped muscle running on
  a horizontal plane along the upper part of the
  mandible.
• It originates in the pterygoid fossa of the
  sphenoid bone and inserts in the condyloid
  (posterior)process.

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External Pterygoid Muscle

• Because the mandible is only hinged at the
  condyloid process, when this muscle contracts, it
  releases the hinge and the coronoid process is
  swung forward and downward in an opening
  movement.
• It is also responsible for side-to-side grinding
  action in rotary chewing by alternating
  contraction and relaxation on each side of the
  mandible.

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The Tongue

• The tongue is an extremely complex structure
  composed of intrinsic and extrinsic musculature.
• It is connected to the hyoid bone, soft palate,
  pharynx, and epiglottis, but its anterior,
  lateral, and superior borders are not connected.

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The Tongue

• The tongue is composed almost entirely of muscle
  fibers going in all directions.
• The muscles are all paired with the exception of
  one.
• The tongue has extensive vascular and neural
  supply to allow it to perform very precise
  movements patterns necessary for the production
  of intelligible speech and for bolus preparation
  and transport.

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The Tongue

• The oral tongue includes the tip, blade, front,
  center, and back, ending at the circumvallate
  papillae.
• The papillae add texture, increase the surface
  area, and assist with taste perception and the
  preparing of foods for digestion.

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The Tongue

• The oral tongue is active during speech and
  during the oral stage of swallow.
• It is under voluntary neural control.
• The pharyngeal tongue, or tongue base begins at
  the circumvallate papillae and extends to the
  hyoid bone.

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The Tongue

• The hyoid bone forms the foundation of the
  tongue, the body of which sits on the hyoid.
• The hyoid bone is embedded in the base of the
  tongue and articulates with no other bone.

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The Tongue

• The pharyngeal tongue is active during the
  pharyngeal stage of swallow.
• It provides anchoring during hyoid elevation and
  upper esophageal sphincter opening.
• It is under involuntary neural control.

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The Soft Palate

• The soft palate, or velum, has dual sphincter
  functions in both speech production and
  swallowing.
• At rest, when it is fully relaxed and resting on
  the tongue base, it acts to divide the oral and
  pharyngeal cavities.

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The Soft Palate

• This state is found during the production of
  nasal sounds, and during the oral phase of
  swallowing.
• It can also be pulled down and forward against
  the back of the tongue by the palatoglossus
  muscle of the anterior faucial arch.

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The Soft Palate

• For non-nasal sound production and during the
  pharyngeal phase of swallowing, the soft palate
  elevates and divides the nasopharynx from the
  oropharynx.
• Elevation and retraction for velopharyngeal
  closure is achieved by a combination of muscles.

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The Soft Palate

• The muscle involved in velopharyngeal closure
  include the palatopharyngeal muscles of the
  posterior faucial arch, the levator veli palatini
  muscles, and the fibers of the superior
  pharyngeal constrictor muscles.

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Oral Mucosa

• Lining the inside of the mouth, and continuous
  with the lining of the pharyngeal spaces, is the
  oral mucosa.
• This mucosa is similar in function to the skin
  that covers the outer body in that it is the
  first line of defense against infections of the
  mouth.

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Oral Mucosa

• The oral mucosa is made of three distinctly
  different types of cells, giving specific
  function to different areas within the mouth.
• The more keratinized tissues with heavy
  underlying connective tissue firmly attach to
  bone.

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Oral Mucosa

• They provide protection to some areas of the
  gingiva and mucosa of the hard palate.
• Mucosa that is less keratinized and lacks the
  underlying thick connective tissue covers the
  other areas of the gingival of the gums, cheeks,
  and floor of the mouth.

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Oral Mucosa

• Very specialized mucosa covers the dorsum of the
  tongue.
• Here taste receptors are abundant and are
  composed of many different specialized cells
  types.
• Taste receptors are also located throughout other
  soft tissues of the mouth.

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Vestibule

• The vestibule is bounded externally by the cheeks
  and lips and internally by the gums and teeth.
• Soft tissue pockets are created by the normal
  juxtaposition of structures in the oral cavity.
• In patients with swallowing disorders, food or
  liquid collects frequently in these natural
  cavities and may remain after the swallow.

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Vestibule

• The soft tissue pockets of the vestibule are the
  lateral sulci, between the alveolus and the
  cheek, and the anterior sulci, between the
  alveolus and the lip musculature, both superiorly
  and inferiorly.

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Vestibule

• The cheeks, muscular structures covered on the
  outside by skin and lined by non-keratinized
  stratified squamous epithelium, form the lateral
  walls of the oral cavity.
• The anterior portions of the cheek terminate in
  the superior and inferior lips.

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Vestibule

• The lips are fleshy folds surrounding the orifice
  of the mouth.
• They are covered on the outside by skin and on
  the inside by a mucous membrane.

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Vestibule

• The transition zone where the two kinds of
  covering tissue meet is called vermilion.
• The vermilion of the lips is nonkeratinized, and
  the color of the blood in the underlying blood
  vessels is visible through its transparent
  surface layer.

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Vestibule

• The inner surface of each lip is attached to its
  corresponding bone by a midline fold of mucous
  membrane called the labial frenulum.

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Vestibule

• The orbicularis oris muscle and connective tissue
  lie between the external covering and the
  internal mucosal lining.
• During chewing, the cheeks and lips help keep
  food between the upper and lower teeth.
• They also assist in speech.

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Anterior Floor of the Mouth

• The hyoid bone is suspended in the soft tissue by
  muscles of the floor of the mouth which originate
  postero-laterally from the region of the temporal
  bone.
• These include the posterior belly of the
  digastric muscle and the stylohyoid muscles.

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Anterior Floor of the Mouth

• Other muscles in the floor of the mouth are
  important for deglutition.
• They elevate the hyoid bone and provide tongue
  stabilization.
• These include the mylohyoid, geniohyoid, and
  anterior belly of the digastric muscle.

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Anterior Floor of the Mouth

• They all attach to the body of the mandible
  anteriorly, and the body of the hyoid bone
  posteriorly.
• The pliability of the floor of the mouth region
  and the attachments of the tongue musculature to
  the anterior mandible allow for tongue mobility
  in the anterior and posterior directions.

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Major and Minor Glands

• The mucous membranes lining the mouth contains
  many small glands, in the tongue, lips, cheeks,
  and the roof of the mouth, that secrete small
  amounts of saliva.
• However, the major portion of saliva is secreted
  by the salivary glands, accessory structures that
  lie outside the mouth and pour their contents
  into ducts that empty into the oral cavity.

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Major and Minor Glands

• Saliva is essential for the maintenance and
  protection of the oral mucosa, teeth, and
  epithelium of the intestinal tract.
• It protects the hard and soft tissues through
  antibacterial, antifungal, antiviral, hydration,
  buffering, and remineralization processes.
• It has lubricating functions that facilitate
  speech, eating, and swallowing.
• It also greatly assists taste perception by its
  cleansing action of taste buds.

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Major and Minor Glands

• The three major salivary glands are the parotid
  glands, the submandibular glands, and the
  sublingual glands.
• The parotid glands are located inferior and
  anterior to the ears between he skin and the
  masseter muscle.

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Major and Minor Glands

• Each gland secretes into the oral cavity
  vestibule via a duct, called the parotid
  (Stensen's) duct, that pierces the buccinator
  muscle of the cheek to open into the vestibule
  opposite the second molar tooth.

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Major and Minor Glands

• The submandibular glands are found beneath the
  base of the tongue in the posterior part of the
  floor of the mouth.
• The submandibular (Whartons)ducts run just under
  the mucosa on either side of the midline of the
  mouth floor and enter the oral cavity on either
  side of the lingual frenulum.

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Major and Minor Glands

• The sublingual glands are anterior to the
  submandibular glands.
• Their ducts, the lesser sublingual (Rivinus's)
  ducts, open into the floor of the mouth in the
  oral cavity proper.

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Major and Minor Glands

• Chemically, saliva is 99.5 water and 0.5
  solutes.
• Among the solutes are salts--chlorides,
  bicarbonates, and phosphates of sodium and
  potassium.
• Some dissolved gases and various organic
  substances including urea and uric acid, serum
  albumin and globulin, mucin, the bacteriolytic
  enzyme lysozyme, and the digestive enzyme
  salivary amylase are also present.

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Major and Minor Glands

• Each saliva-producing gland supplies different
  proportions of ingredients to saliva.
• The parotids contain cells that secrete a watery
  serous liquid containing the enzyme salivary
  amylase, which works on starches and is vital in
  moistening the food to facilitate chewing and
  swallowing

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Major and Minor Glands

• The submandibular glands contain cells similar to
  those found in the parotids and some mucous
  cells.
• Therefore, they secrete a fluid that is thickened
  with mucous, but still contains quite a bit of
  enzyme.
• The sublingual glands contain mostly mucous cells
  so they secrete a much thicker fluid that
  contributes only a small amount of the enzyme to
  the saliva.

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Major and Minor Glands

• The water in saliva provides a medium for
  dissolving foods so they can be tasted, and for
  initiating digestive reactions.
• The chlorides in the saliva activate the salivary
  amylase.
• The small glands on the circumvallate papillae of
  the tongue secrete a lingual lipase, which
  briefly mixes with food, and will later help with
  beginning fat digestion.

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Major and Minor Glands

• The bicarbonates and phosphates buffer chemicals
  that enter the mouth and keep the saliva at a
  slightly acidic pH of 6.35 to 6.85.
• Urea and uric acid are found in saliva because
  the saliva-producing glands help the body to get
  rid of wastes.
• Mucin is a protein that forms mucous when
  dissolved in water.
• Mucus lubricates the food so it can be easily
  moved about in the mouth, formed into a ball, and
  swallowed.

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Major and Minor Glands

• The mouth carries pathogenic bacteria, that, if
  uncontrolled, can harm oral tissues and cause
  dental caries
• The constant flow of saliva helps to wash away
  the bacteria and food particles on which they
  feed
• The enzyme lysozyme destroys bacteria, protecting
  the mucous membrane from infection and the teeth
  from decay.
• Swallowed saliva is also natural neutralizer of
  stomach acid.

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Major and Minor Glands

• Food stimulates the salivary glands to secrete
  heavily.
• When food is taken in the mouth, chemicals in the
  food stimulate receptors in taste buds on the
  tongue.
• Impulses are conveyed from the receptors to two
  salivary nuclei in the brainstem called the
  superior and inferior salivatory nuclei.
• The salivary nuclei are located at the juncture
  of the pons and medulla.
• They send signals to the salivary glands via the
  parasympathetic nervous system.

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Major and Minor Glands

• Normal salivary secretion ranges from 1.0 to 1.5
  liters per day.
• Moderate amounts of saliva are continuously
  secreted in response to parasympathetic
  stimulation to keep the mucous membranes moist
  and to lubricate the movements of the tongue and
  lips during speech.
• This saliva is then swallowed and reabsorbed to
  prevent fluid loss.
• Salivation also occurs in response to swallowing
  irritating foods or during nausea.
• Reflexes originating in the stomach and upper
  small intestine stimulate salivation.

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Major and Minor Glands

• This mechanism presumably helps to dilute or
  neutralize the irritating substance.
• Saliva continues to be secreted heavily some time
  after food is swallowed.
• This continued flow washes out the mouth and
  dilutes and buffers the chemical remnants of
  irritating substances.
•  Dehydration causes the salivary glands to cease
  secreting saliva to conserve water, which, if
  chronic, can lead to a bacterial imbalance in the
  oral cavity.