Fluoroscopic investigation of pharyngeal function in the horse.

This research study utilized videofluoroscopy to examine the swallowing reflex in horses considered to have normal throat and larynx function. The reflex was found to be the same as in humans and rabbits; however, a unique characteristic in horses was found; their auditory tube diverticuli (guttural pouches) temporarily enlarged due to the contraction of the throat muscles during swallowing.

Overview of the study

• This research used videofluoroscopy, a type of imaging technique that captures moving images of internal structures and can observe dynamic physiological processes like swallowing, to study the swallowing reflex in horses.
• The examined horses were believed, based on endoscopic and clinical examination, to have normal pharyngeal (throat) and laryngeal (larynx or voice box) function.

Key findings

• The study found that the swallowing reflex in the horses was the same as the one described in humans and rabbits. This pattern of throat muscles contracting and relaxing in a specific process allows the safe passage of food from the mouth to the stomach, preventing choking and aspiration into the lungs.
• An interesting feature observed was that during the swallowing reflex, the horses’ auditory tube diverticuli, also known as guttural pouches, increased in size temporarily. This is a pair of large, air-filled sacs that are not present in humans and not fully understood, but may aid in cooling the blood flowing to the brain or act as resonating chambers for vocal sounds.
• This temporary increase in size of the guttural pouches was due to the contraction of the pharyngeal muscles during swallowing. The researchers hypothesized that this could possibly play a role in preventing ear discomfort or pain during swallowing due to the changes in pressure.

Implications of the findings

• The similarities of the swallowing reflex across species including horses, humans, and rabbits, suggests a relatively consistent evolutionary pattern for this essential physiological function.
• The study’s findings suggest new understanding of the role and function of the auditory tube diverticuli (guttural pouches) and the pharyngeal muscles in horses, providing opportunities for further research and potential clinical applications in managing diseases that affect swallowing and hearing in horses.