Anatomical and Physiological Parameters that Influence Gastrointestinal Absorption

Abstract

The rate at which ingested compounds are absorbed into the bloodstream from the gastrointestinal (GI) tract and extent to which they are absorbed are governed by the physical‐chemical properties of the ingested compounds, the presence and identity of other substances in the GI tract, and the anatomical and physiological characteristics of the GI tract. This chapter describes the anatomical and physiological similarities and differences between humans and some common laboratory animals, with an emphasis on the absorptive surface area of the GI tract, the time it takes for materials to move through the GI tract, and the nature of the GI contents.

Canine gastrointestinal physiology: Breeds variations that can influence drug absorption

“…98 Although we have segregated the discussion into discrete topics, 99 it is important to recognize that the GI tract should be viewed from 100 the perspective of an interacting and dynamic system. The total length of the canine small intestine is comprised 103 approximately 10% duodenum, 85% jejunum and 5% ileum [1]. 104 The dog small intestine is lined by villi and does not show the pres-105 ence of the permanent folds (plicae circulares) that serve to 106 increase the effective absorptive surface area of humans and pri-107 mates.…”

Blood Sampling From Rat Ileal Mesenteric Vein Revealed a Major Role of Dietary Protein in Meal-Induced GLP-1 Response

“…Insulin is not secreted from the intestine, and its secretion is stimulated by multiple factors such as GLP-1, GIP, glucose, amino acids, and fatty acid in the plasma, therefore, we are not able to provide relevant reasons for similar insulin responses observed in the present study regardless of the regions of blood sampling and of the diets given (Supplementary Figure 1). Concentrations of plasma gut hormones could be affected by the rate of blood flow and by merging with the blood outside from the intestine such as the pancreas and kidney (29). Portal blood flow is increased by meal ingestion and plasma glucose (30)(31)(32)(33).…”

Comparative anatomy, pre‐ and postnatal changes during the development and maturation of the small intestine: Life‐stage influences on exposure

“…Because the major site of absorption is the small intestine, the present report will focus on the cross‐species differences in the anatomical and physiological development of the pre‐ and postnatal small intestine. Interspecies diversity in the adult anatomy of the alimentary tracts and the impact on absorption have been described elsewhere (DeSesso & Jacobson, 2001; DeSesso, Jacobson, & Lavin, 2012; DeSesso & Williams, 2008), but will be briefly reviewed below.…”