Anatomy and Physiology of Swallowing

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Introduction

Deglutition is the process of swallowing which defines the movement of liquids or solids from the mouth to the stomach via the pharynx and esophagus. This process accommodates the changes in development as well as changes related to pathology associated with dysphagia. The elements of swallowing such as the suck, swallow, and breathing sequence evolve in the early stages of development and end with a conscious action of swallowing. Multiple organ systems are involved in this process and include musculoskeletal system, neuromuscular system and respiratory system. Normal swallowing requires a coordinated effort of over thirty muscles , the central nervous system, and six cranial nerves. Additionally the nose, the nassal cavity, the oral cavity, and the pharynx are key anatomy structures involved in this process. This article explores anatomy and physiology pertain to the process of normal swallowing.

Developmental Anatomy and Swallowing

Anatomical differences in the swallowing structures are present from infant, through older child, to adulthood. Alongside the anatomical changes , the swallowing adaptation occurs.

Infant:

• jaw and oral cavity are small
• tongue takes up most of the capacity of the mouth
• no teeth
• sucking is possible by using the tongue, sucking pads, and sulci
• sucking pads provide stability
• lack of distinct oropharynx
• the size of the larynx is 1/3 of an adult larynx and is located higher in the laryngeal cavity
• the base of the tongue is close to the larynx
• vocal cords consists of 1/2 of cartilage
• the epiglottis and soft palate touch when at rest

Older child:

• tongue lies at a lower position (floor of the mouth) because the mouth is bigger and the tongue sits behind the teeth
• the mandible extends down and forward
• the oral cavity expands
• the hyoid and larynx are positioned further down
• buccinators (cheek muscles) generate sucking mechanism
• the tongue pushes the food laterally to allow chewing with the teeth
• the sucking pads degenerate
• the pharynx lengthens vertically
• the nasopharynx becomes a 90-degree angle
• the epiglottis becomes wide and flattened
• the base of the tongue and the larynx separate by the age 4
• true vocal cords consist of no more than 1⁄3 of cartilage
• larynx starts to lower by the age of 2

Note: the changes listed above occur at the compromise of aspiration. These changes make the patient prone to aspiration but they are important for speech.

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