To the respiratory physiologist or anatomist the diaphragm muscle is of course the prime mover of tidal air. However, gastrointestinal physiologists are becoming increasingly aware of the value of this muscle in helping to stop gastric contents from refluxing into the oesophagus. The diaphragm should be viewed as two distinct muscles, crural and costal, which act in synchrony throughout respiration. However, the activities of these two muscular regions can diverge during certain events such as swallowing and emesis. In addition, transient crural muscle relaxations herald the onset of spontaneous acid reflux episodes.
Studying the motor control of this muscular barrier may help elucidate the mechanism of these episodes. In the rat, the phrenic nerve divides into three branches before entering the diaphragm, and it is possible to sample single neuronal activity from the crural and costal branches.
This review will discuss our recent findings with regard to the type of motor axons running in the phrenic nerve of the rat. In addition, we will outline our ongoing search for homologous structures in basal vertebrate groups. In particular, the pipid frogs (e.g. the African clawed frog, Xenopus laevis) possess a muscular band around the oesophagus that appears to be homologous to the mammalian crural diaphragm. This structure does not appear to interact directly with the respiratory apparatus, and could suggest a role for this region of the diaphragm, which was not originally respiratory.
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Escrito por Leandro Marques da Silva , Elizângela de Sousa Monteiro , Bruno Silva Miranda , Clesio Rafael Lopes da Silva , Anne Shirley Menezes Costa
Escrito por Anelise Zimmermann de Ajambuja1 ; Paloma Lopes Francisco Parazzi2 ; Lilian Gerdi Kittel Ries3 ; Camila Isabel Santos Schivinski3
Escrito por Alana Bortolan Sacon1 Ana Paula Pillatt2 Laura Wuttig Berbam3 Vanessa Zardin Fengler4 Darlene Costa de Bittencourt5 Adriane Schmidt Pasqualoto6