Neuromuscular Specializations of the Human Hypopharyngeal Muscles.

The hypopharyngeal muscles in humans play a vital role in swallowing, speech, and respiration. Increasing evidence indicates that these muscles are specialized to perform life-sustaining upper aerodigestive functions. This review aims to provide current knowledge regarding the key structural, physiological, and biochemical features of the hypopharyngeal muscles, including innervation, contractile properties, histochemistry, biochemical properties, myosin heavy chain (MyHC) expression and regulation, and age-related alterations. These would clarify the unique neuromuscular specializations of the human hypopharyngeal muscles for a better understanding of the functions and pathological conditions of the pharynx and for the development of novel therapies to treat related upper airway disorders.