Surface area of the small intestine in man.

Abstract

EDITORIAL COMMENT This paper sets out the principles for measuring the surface area of small intestine and demonstrates that it decreases sharply from proximal to distal intestine.Despite wide interest in the small intestine brought about by modem biopsy techniques and absorption studies, quantitative knowledge of the basic structure of the small intestine remains slight.The irregularity of the mucosal surface caused by the villi and the submucosal folds increases the area available for absorption. The size and distribution of the villi and folds vary from one end of the intestine to the other and there is, therefore, a variation in mucosal area per centimetre length along the intestine.Early attempts were made to estimate mucosal surface area by measuring and counting individual villi. These gave widely varying results (Heidenhain, 1888;Krogh, 1929 In this study the mucosal area at different levels has been measured in human intestine obtained at necropsy after fixation in situ. METHODSAt necropsy, with the minimum of handling, ties were placed around the proximal jejunum and terminal ileum. A T-shaped cannula was tied into the most prominent presenting loop of intestine and the gut distended to a pressure of 40 cm. H.0 with 40% formaldehyde. After leaving the gut undisturbed for one hour it was removed with its mesentery and placed in formol saline for a further 24 hours. It was then closely shom of its mesentery, its length measured, and samples cut out at measured intervals from the duodeno-jejunal flexure. From each site two samples, about 4 cm. in length, were taken, one circumferential and one longitudinal. Care was taken to cut the circumferential specimen between and parallel to the submucosal folds.After embedding in paraffin, histological sections were cut at a thickness of 5 & and stained with haematoxylin and eosin. Sections were then projected at a linear magnification of 100 on to tracing paper and the outlines of mucosa, muscularis mucosae, and serosa traced in pencil. Measurements of the tracings were made with an opisometer calibrated in centimetres.Material from six necropsies was studied. The causes of death were renal failure, carcinoma of the bronchus, vulva, and kidney, and, in two cases, myocardial ischaemia. Ages ranged from 38 to 81.

Translating Human Effective Jejunal Intestinal Permeability to Surface-Dependent Intrinsic Permeability: a Pragmatic Method for a More Mechanistic Prediction of Regional Oral Drug Absorption

“…It has been shown, however, that the amplifications in mSA generated by the circular folds and villi decrease from the proximal SI to the distal SI. In addition, a decrease in mSA has been observed from the colonic microvilli compared to that of the small intestine (36,39).…”

“…This method was based on the work by Wilson (1967), who reported a correlation between the mSA and the longitudinal position between the beginning of the jejunum (duodenojejunal flexure, DJF) and the final portion of the ileum (ileocecal valve, ICV) (36). This method accounts for the amplification in SA product of the presence of circular folds and villi along the SI (Fig.…”

“…The aim of this study was to derive regional intestinal permeability estimates by translating the observed differences in intestinal mucosal surface area along the different segments of the human intestine (36,37) into the human P eff values and to evaluate the ability of the new permeability values to predict the GI absorption using a semi-mechanistic PBPK absorption model.…”

Do most lymphocytes in humans really reside in the gut?

“…underneath the epithelium). However, the above-stated estimate of the gut surface includes microvilli, which do not harbor any lymphocytes; the surface area of the gut excluding microvilli is much smaller, on the order of 2-10 m 2 [25,26]. Second, it has been estimated that up to 80% of all IgA-producing plasma B cells in mice and humans are located in the gut, arguing for a large population of lymphocytes at this site [27,28].…”

Zebrafish Offers New Perspective on Developmental Role of TOR Signaling

“…A clue may be found in the general correlation between intestinal surface area and body size, 16 which makes intuitive sense but whose underpinning is unknown. We propose that TOR signaling may represent the common link between body size and intestinal surface area.…”