Feeding and the Swallow Mechanism

Why is Feeding Important for the Development of Children

Feeding is extremely important for the development of the motor and cognitive functions = food is essential nourishment for brain development!

Definition of Deglutition

Swallowing or deglutition is the process by which food passes from the mouth through the fairings and into the esophagus. 

As simple as it might seem to healthy people, swallowing is actually a very complex action that requires an extremely precise coordination with breathing since both of these processes share the same entrance the fairings. Failure in coordination would result in choking or pulmonary aspiration.

Swallowing involves over 20 muscles of the mouth throat and esophagus which are controlled by several cortical areas and by the swallowing centers in the brain stem. The brain communicates with the muscles through several cranial nerves.

As a disorder of posture and movement, children with cerebral palsy can manifest significant feeding difficulties. [1]

Swallowing Mechanism

In order to understand the possible risk involved if the child has swallow coordination difficulties it may be helpful to know the anatomical part involved in swallowing (Fig. 1) and to understand the complexity of the swallowing mechanism that is composed by 3 main phases (Fig. 2).

Swallow 1.png
Swallow 2.png
Fig. 1 Fig. 2


 [2]

Phase 1: Oral Phase

This process is the only voluntary part of swallowing and it is under neuro control of several areas of cerebral cortex including the motor cortex.

  • Food is moistened with saliva and food bolus is formed
  • The tongue pushes the bolus to the back of the throat (the fairings)
  • It starts with lip closure (if the mouth keeps open the jaw doesn’t have any stability, very difficult to swallow)

Phase 2: Pharyngael Phase

  • Starts with stimulation of tactile receptors in the oropharynx, swallow reflex is initiated (that’s why sensory problems can affect the initiation of this phase on compromise swallow reflex)
  • Soft palate lifts to cut off nasal airways
  • Bolus moves over back tongue and the tongue blocks the oral cavity to prevent the food going to the oral cavity
  • Epiglottis is pushed backward over larynx
  • Larynx and vocal folds contract covering the entry of the trachea to protect airways, respiration temporary arrested (this is the most important step since entry of food or drink into the lungs may potentially be life-threatening; we stop breathing when we swallow at any stage of development-protective reaction)
  • Upper esophageal sphincter opens to allow passages to the esophagus

Phase 3: Oesophageal Phase

  • Food bolus is propelled down the esophagus by peristalsis (a wave of muscular contraction that pushes the bolus down)
  • The larynx moves down back to the original position

Development of Eating and Drinking

Feeding in infant is largely driven by the reflexes that are present at birth. Although there is some refinement over the first few weeks of life, most children born at term can feed well enough to gain weight and grow thanks to adequate coordination of suck-swallow-breath cycle (children born premature might need time to develop their skills and therefore face feeding difficulties-nasogastric tube feeding can be used initially, but when removed this can lead to delay in oral motor development linked to hyposensitivity).

New born baby infantile reflexes:

  • Rooting (Turning toward stimulation around the mouth, useful for breast feeding)
  • Sucking (On nipple/teat/finger/dummy placed in the mouth)
  • Swallow (Airway cleaning procedure because saliva is felt at the back of the pharynges and this triggers the swallow reflex)

Oral Protective Responses:

  • Gagging (Preventing foreign bodies entering the airways)
  • Cough (To clear airways)

N.B: their presence is not evidence of safe deglutition, as well if we don’t see any oral responses it doesn’t mean the child feeding is safe-poor sensation lead to silent aspiration (the reflexes are triggered by sensation).
New-born babies and adults have important anatomical differences justified by the fact that babies have an immature brain therefore their responses can’t be sophisticated and adaptable to all the variable like the adult’s one (liquid and solid food, mixed textures etc.). These adaptive responses request a high level of coordination and develop with physiological adaptations that allow the child to cope with the changes of diet that occur through infancy, the introduction of complementary foods and the transition to family foods. The maturation of more refined chewing and swallowing abilities completes at the 3rd-4th year of life.

 [3]

Oral Control Development Summary

1st Trimester

Key Features 1st Trimester (Birth - 3 Months)

  • Predominant fw/bw movements of tongue with more jaw excursion
  • Feeding set off by infantile responses
  • Tongue flat and cupped
  • Swallow triggered by suck (Only liquids)

1 Trimester.png

2nd Trimester

Key Features 2nd Trimester (4 - 6 Months):

  • It begins maturation of voluntary control of muscle involved in eating
  • Still suck-swallow but tongue begins to move also upward and less jaw excursion
  • Tongue protrudes in transfer of food to pharynx (Pushing semi solid food out of the mouth)
  • Semisolids-smooth purée is introduced (Tongue still not very sensitive)
  • Mouth opens when spoon approaches
2 Trimester 1.png 2 Trimester 2.png

3rd Trimester

Key Features 3rd Trimester (6-9 Months):

  • Lateral closure of lips
  • Jaw movements can be separated from mouth and lips (starts dissociation)
  • Finger feeding
  • Tongue moves to the side but doesn’t cross midline
  • Lower lip draws spoon in, upper lip clears
  • Around 7th months introduction of lumpy purée and more solid texture-link with mouthing at age 4-5 months = children put everything in their mouth to move further back the GAG response for them to be able to start eating solid food safely and to develop new pattern of movement required to handle more challenging texture (differentiated tongue movements). CP children don’t get the chance to experiment solids in their mouth sometimes and therefore get ready for feeding, when they experience food they have traumatic reactions.
3 Trimester 1.png 3 Trimester 2.png

4th Trimester

Key Features 4th Trimester (10-12 Months):

  • Refinement - More coordination - Effective chew - Better management of solid food
  • Reduced up/down movements of jaw when drinking from cup
  • Controlled bite
  • Active use of chicks to draw food in and keep it
  • Reaches forward to spoon and clear
  • Longer sequence of swallowing liquids without spilling

4 Trimester 1.png

4th Trimester - 3 Years

Key Features 4th Trimester to 3 years:

  • Skills continue to refine
  • Smoother movements
  • Better grading mouth opening
  • More sustained bite through harder textures
  • Use of tongue, teeth or fingers to clear food off lips
  • Easy transfer of bolus across midline
  • Increased pace
  • Control on adult size spoon
3 Years 2.png 3 Years 1.png

Recent Related Research (from Pubmed

References 

  1. Finnie NR. Handling the Young Child with Cerebral Palsy at Home. Elsevier Health Sciences; 1997.
  2. All Medical Media - Swallowing Reflex, Phases and Overview of Neural Control, Animation. Available from: https://www.youtube.com/watch?v=YQm5RCz9Pxc [last accessed 16/02/2018]
  3. Peggy S. Eicher: Center for Pediatric Feeding and Swallowing at St. Joseph Children's Hospital New Jersey - Oral Motor Development; Swallow. Available from: https://www.youtube.com/watch?v=-xkiS46IBoE [last accessed 16/02/2018]