Résumé
La physiologie anorectale fait intervenir trois organes: deux organes réservoir (le côlon et le rectum) et un organe résistif (le canal anal entouré de l’appareil sphinctérien lisse et strié). L’arrivée des matières dans l’ampoule rectale va être à l’origine de deux phénomènes: 1) la perception de plénitude rectale; 2) le réflexe d’échantillonnage. À partir de là, et en fonction des conditions environnementales, le sujet sera capable de différer ou de satisfaire son besoin exonérateur. Lors de la défécation, la force d’expulsion du bol fécal est engendrée, d’une part, par la contraction de l’ampoule rectale associée à une fermeture de la charnière rectosigmoïdienne et, d’autre part, par un phénomène propulsif assuré par une augmentation de la pression intra-abdominale associée à une activité contractile du rectum. De façon concomitante, les sphincters anaux interne et externe se relâchent assurant ainsi une parfaite synergie rectosphinctérienne.
Abstract
Anorectal physiology involves three organs. Two of these are reservoirs: the colon and the rectum. The third is an organ of resistance: the anal canal surrounded by the smooth and striated muscle of the sphincteric apparatus. The arrival of material in the rectal ampulla initiates two phenomena: the recognition of rectal filling and the sampling reflex. From then on, and depending on environmental conditions, the subject will be able to satisfy or defer the need to empty his rectum. During defaecation, the force of expulsion of the faecal mass is generated both by contraction of the rectal ampulla combined with closure of the rectosigmoid junction and by propulsion resulting from contractile activity of the rectum and an increase in intra-abdominal pressure. At the same time, the internal and external anal sphincters relax, thus ensuring perfect recto-sphincteric coordination.
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Gallas, S., Leroi, AM. Physiologie de la défécation. Pelv Perineol 5, 166–170 (2010). https://doi.org/10.1007/s11608-010-0337-7
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DOI: https://doi.org/10.1007/s11608-010-0337-7