Gut hormones

At the end of the last century Pavlov proposed that the control of alimentary function was by nervous reflex.His explanation was intellectually satisfying and a great advance on previous extremely woolly theories.Histologically fine nerve fibres which could be seen running in the gut w& and sectioning the main nerve trunks undoubtedly affected gastrointestinal function.Meanwhile, however, Brown Sequard, attempting to rejuvenate his ageing body, was able to show that extracts of testes greatly increased his prowess in several directions.His findings, published in 1889, caught the public imagination and by the end of the century extracts of numerous organs were available for the purpose of treating real and imagined ailments.Thus when Bayliss & Starling were investigating the influence of the duodenum on the exocrine pancreas, the idea of making duodenal extracts came readily.They were astonished to find that such an extract had all the effects on the exocrine pancreas that had been previously attributed to Pavlov's nervous reflexes.They proposed that there must be a chemical messenger released from the duodenum which acted via the circulation and proposed the term hormone. Nature of the gut endocrine systemAlthough the first substance to be named hormone, secretin, was from the alimentary tract, progress in the understanding of gut endocrinology was very slow.Histology, and later ultra-structural examination, showed the gut to contain many different types of endocrine cells.These, however, were scattered diffusely through the mucosa and not gathered together to form an endocrine gland.The gastrointestinal tract is thus an example of the diffuse endocrine system.The many different types of endocrine cells are spread widely, and in overlapping configuration, throughout the gastrointestinal mucosa.This is because they are required to respond to a similarly diffuse signal.Thus a representative subject may 37 (3) 4