Small intestine physiology

Vertzoni M, Fotaki N, Kostewicz E, Stippler E, Leuner C, Nicolaides E, Dressman J, Reppas C (2004) Dissolution media simulating the intralumenal composition of the small intestine Physiological issues and practical aspects. J Pharm Pharmacol 56 453 162... 

As we have seen in this chapter steroids have a number of functions in human physiology Cholesterol is a component part of cell mem branes and is found in large amounts in the brain Derivatives of cholic acid assist the digestion of fats in the small intestine Cortisone and its derivatives are involved in maintaining the electrolyte balance in body fluids The sex hormones responsible for mascu line and feminine characteristics as well as numerous aspects of pregnancy from conception to birth are steroids... 

JS Trier. Morphology of the epithelium of the small intestine. In CF Code, ed. Handbook of Physiology. Vol. Ill, Intestinal Absorption. Washington, DC American Physiological Society,1968, p. 1133. 

JL Madara, JS Trier. Functional morphology of the mucosa of the small intestine. In LR Johnson, ed. Physiology of the Gastrointestinal Tract. 2nd ed. New York Raven, 1994. 

The Leggett Model simulates lead biokinetics in liver with two compartments the first simulates rapid uptake of lead from plasma and a relatively short removal half-life (days) for transfers to plasma and to the small intestine by biliary secretion a second compartment simulates a more gradual transfer to plasma of approximately 10% of lead uptake in liver. Different transfer rates associated with each compartment are calibrated to reproduce patterns of uptake and retention of lead observed in humans, baboons, and beagles following intravenous injection, as well as blood-to-liver concentration ratios from data on chronically exposed humans. Similarly, the Leggett Model simulates lead biokinetics in three compartments of soft tissues, representing rapid, intermediate, and slow turnover rates (without specific physiologic correlates). 

Because of fermentation processes, the luminal environment of the colon is slightly acidic at a pH value around 6.6 [2], Similar pH values can be found in the upper small intestine (pH 6.5 and pH 6.7, in the duodenum and jejunum, respectively), whereas in the ileum the pH is slightly higher at a neutral to alkaline pH value around 7.1 [2], Therefore, the slightly acidic solutions, which are generally used for maintaining physiologically relevant luminal conditions... 

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