HISTOCHEMICAL AND MORPHOMETRIC PROPERTIES OF MUSCLES OF THE UPPER AIRWAY OF GOATS

This study investigated the histochemical and morphometric properties of fibres in laryngeal, hyoid, tongue and pharyngeal muscles which con tribute in maintaining patency of the upper airway. Muscle specimens f rom adult female goats were stained for nicotinamide adenine dinucleot ide dehydrogenase-tetrazolium reductase and myosin adenosine triphosph atase activities, and the composition and size of the fibre types dete rmined. These muscles contained types 1, 2A, 2B and 2C fibres with typ e 2 fibres predominating and the fibres possessed oxidative enzyme act ivity suggesting fast contraction speed and yet moderate resistance to fatigue. Abductor laryngeal muscles contained more type 1 fibres than the adductors. Among pharyngeal muscles fibre size and type 1 fibre c omposition increased progressively from the hyopharyngeus caudally. Up per airway muscles contained relatively small fibres (range of mean di ameter: 25.7 to 46.1 mum) with the pharyngeal and lingualis proprius m uscles containing the smallest fibres. These properties might influenc e the response of upper airway muscles to neuromuscular blocking drugs .