Digesta Viscosity and Glucose Behavior in the Small Intestine Lumen
Conversely, glucose can reach the epithelium via di¬usion in laminar ow (Figure 14.1) [3]. If the di¬usion rate of glucose in the lumen is lower than its transepithelial absorption rate, the overall absorption rate of the glucose should be proportional to either its di¬usion rate in the lumen or its...
Saved in:
Published in | Dietary Fiber and Health pp. 204 - 215 |
---|---|
Format | Book Chapter |
Language | English |
Published |
United Kingdom
CRC Press
2012
Taylor & Francis Group |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | Conversely, glucose can reach the epithelium via di¬usion in laminar
ow
(Figure 14.1) [3]. If the di¬usion rate of glucose in the lumen is lower than its
transepithelial absorption rate, the overall absorption rate of the glucose should
be proportional to either its di¬usion rate in the lumen or its membrane transport rate. ´e slower of these two factors is the rate-limiting factor for the overall
absorption process. Considering the mentioned short-chain fatty acid gradient
and heterogeneous distribution of microbiota across the intestinal lumen [6,7],
the di¬usion rate in the lumen should be slower than the membrane transport
rate. ´erefore, the di¬usion rate of glucose in the lumen should correlate with
the overall absorption rate in laminar
ow (Equation 14.2):( ) ( ),Overall absorption rate Diffusion rate in lumen= b (14.2)where b is a constant.
´e
ow behavior of digesta in the lumen can be estimated using the Reynoldsnumber, which expresses the ratio of inertial forces to viscous forces in a
uid [8].
´e inertial force is the tendency of the
uid to stay in motion or at rest unless
acted upon by an outside force [9]. ´e viscous force is an internal property of a
uid that o¬ers resistance to
ow [9]. ´e Reynolds number is used to determine
whether a
ow will be dominated by inertial or viscous forces, i.e., whether the
ow is turbulent or laminar. A Reynolds number below 2300 indicates that viscous
force predominates over inertial force to keep the
ow laminar (Figure 14.2a),
which results in poor micromixing along the transverse axis. Conversely, a
Reynolds number exceeding 2300 indicates that inertial force dominates and that
the
ow has become turbulent [8] (Figure 14.2b), which completely mixes digesta
at the molecular level [4]. |
---|---|
ISBN: | 9781439899298 1439899290 |
DOI: | 10.1201/b12156-17 |