Author(s):
Rodrigues, Manuel Lima 
; Fernandes, Ana Valle ; Nunes, Rui ; Almeida, Armando
Date: 2006
Persistent ID: http://hdl.handle.net/1822/5185
Origin: RepositóriUM - Universidade do Minho
Subject(s): Motor end plates distribution; Thyroarytenoid muscle; Syringeal muscle; Cricoarytenoid muscle;; Vertebrates
Description
Vertebrates are capable of producing a variable sound spectrum. In mammals, lissamphibia,
and reptiles, the larynx is the vocal organ responsible for sound production, whereas
in birds it is produced by the syrinx, an avian organ located at the base of trachea. The
distribution of neuromuscular junctions responsible for the fine control of laryngeal muscle
(LM) and syringeal muscle (SM), although studied with some detail in human LM, remains
mostly unknown in other vertebrates. In the present study, we analyzed the distribution of
motor end plates (MEPs) in LM/SM of different vertebrate classes using the histochemical
detection of acetylcholinesterase: the thyroarytenoid and cricoarytenoid LM of mammal
(human, rat, and rabbit) and cricoarytenoid LM of nonmammalian (frog and avian) species
and the tracheobronchial SM of rooster and pigeon. In humans and frogs/avians, MEPs were
distributed diffusely along, respectively, the thyroarytenoid-cricoarytenoid and the cricoarytenoid
LM fibers, whereas in rats and rabbits, MEPs were concentrated in a transverse band
located in the middle of thyroarytenoid and cricoarytenoid muscle fibers. In roosters and
pigeons, MEPs were distributed diffusely along SM fibers. The highly diffuse MEP distribution
along human thyroarytenoid and cricoarytenoid fibers indicates that these muscles can
markedly change their degree of contraction, which may contribute for the large range of different
sounds produced by human vocal folds. The same rationale was applied to discuss the possible
functional significance of the morphological distribution of MEPs along the LM/SM of the other
vertebrates analyzed.
