The anatomy of a swallow: The complex process that can challenge children with PFD

Published by Georgia A. Malandraki, PhD, CCC-SLP, BCS-S, F-ASHA on Jun 12, 2024

The process of swallowing that most people take for granted is a remarkably intricate series of sensory and motor events. Developing effective treatments to support children with pediatric feeding disorder (PFD), who struggle with swallowing, requires understanding the specific physiological deficits in each child, rather than relying on generalized approaches.

Far from being a simple reflex, it involves coordinated, complex actions by muscles, nerves and sensory organs. When one step of this process is not automated, swallowing is difficult, uncomfortable and even dangerous.

The more researchers and clinicians understand the swallowing process, the better clinicians can support children with PFD.

Four Stages

Initially thought to be a simple reflex, swallowing is now understood to be a complex process involving both automatic and voluntary neural control. In early fetal development, swallowing is reflexive, but as infants grow, the process becomes a learned behavior and eventually a patterned response.

Swallowing can be divided into several stages, each involving distinct anatomical landmarks and physiological processes:

  1. Pre-oral stage: This stage occurs before food or liquid enters your child’s mouth. When seeing and smelling food, your child makes a cognitive decision about whether or not to eat it. This simply means opening the mouth to accept the offering or reaching for food.
  2. Oral stage: Once food enters the mouth, your child processes sensory inputs such as taste, texture and temperature. The child manipulates the food by chewing and mixing it with saliva, preparing to swallow. This stage is primarily controlled by the brain, allowing voluntary actions like chewing and spitting.
  3. Pharyngeal stage: When the food reaches the back of the tongue, a reflex triggers the pharyngeal swallow. This stage is more automatic and involves quickly moving food through the throat into the esophagus while protecting the airway.
  4. Esophageal stage: The food passes through the esophagus to the stomach. This stage involves automatic sensory and motor processes within the esophagus.

Understanding the swallow in pediatrics

A child swallowing water through the straw of a blue water bottle.

Understanding swallowing in children presents unique challenges. While adult swallowing has been studied extensively, pediatric research is limited due to ethical and practical constraints. However, the fundamental principles are similar, with the process becoming more complex around five to six months of age when infants start consuming solid foods.

The first swallow movements in utero occur around 12 to 15 weeks of gestation. At this stage, we believe it’s completely reflexive. Once a baby is born and it becomes more complex and less automatic, part of the process becomes a learned, patterned response. This is likely around five or six months when infants start sitting and consuming solid food.

Diagnosis and treatment of swallowing disorders

Because swallowing is so complicated, there’s no cookie-cutter approach to treating a swallowing disorder. The first step to help a child with PFD is diagnosing the cause of the disorder. This evaluation ideally should involve a multidisciplinary team of experts, such as neurology, ENT and speech-language pathologists. If that’s not possible, the evaluating clinician should at least understand the anatomy, physiology and neurophysiology of swallowing.

Key diagnostic tools for evaluating swallowing include:

  1. Cranial nerve assessment: Cranial nerves are the nerves that innervate the muscles and the sensory components of the head and neck, including during swallowing. An assessment of these nerves is done by a specialist who can evaluate the motor and sensory components of the head and neck. This goal is to gather detailed information about muscle function and sensory perception –– such as strength, range of motion, reflexes, abnormal movements and sensory components.
  2. assessments: Endoscopy and video fluoroscopy are common techniques for assessing swallowing, though they have limitations, such as radiation exposure in children.
  3. Manometry or electromyography: These tools measure pressure and muscle activity, offering insights into the strength and function of swallowing muscles.

Challenges and future goals for supporting children with swallowing disorders

Despite it’s complexity, there are few standardized treatments, especially for children. This stems from a limited understanding of the underlying mechanisms of swallowing disorders.

Without knowing the mechanism causing a swallowing disorder, clinicians and parents are left to compensate to overcome children’s challenges by thickening liquids and adjusting nipple sizes or flow rates. This helps feed the struggling infant, but it doesn’t treat the disorder.

By understanding the anatomy and physiology of swallowing, as well as the challenges in diagnosing and treating disorders, clinicians can better support children with PFD and their families.

Georgia Malandraki, PhD is a professor of speech, language, & hearing sciences at Purdue University.