Intestinal tube

Sinko et al. [32] extended the macroscopic mass balance approach to include chemical and enzymatic degradation, where only highly soluble drugs were taken into account. When the effect of degradation is considered, the total loss in the intestinal tube becomes... 

An algorithm is built from first principles, where the system structure is recreated and subsequently the drug flow is simulated via Monte Carlo techniques [216]. This technique, based on principles of statistical physics, generates a microscopic picture of the intestinal tube. The desired features of the complexity are built in, in a random fashion. During the calculation all such features are kept frozen in the computer memory (in the form of arrays), and are utilized accordingly. The principal characteristic of the method is that if a very large number of such units is built, then the average behavior of all these will approach the true system behavior. 

Passing down the intestinal tube, the effective pore size through the epithelium decreases, so the upper (proximal) gut is more permeable to water than the lower (distal) gut the distal intestine can actually absorb water better than the proximal gut. The observed differences in permeability to water across the epithelium are due almost entirely to differences in conductivity across the paracellular path tight junctions vary considerably in tightness along the length of the gut. 

The large intestine is concerned primarily with the absorption of water and the secretion of mucus to aid the intestinal contents to slide down the intestinal tube. Villi are therefore completely absent from the large intestine, but there are deep crypts distributed over its surface. 

The use of nanocellulose has been suggested in different areas of medicine as substitute of blood vessels and linfatics (Yamanaka et al. 1990 Klemm et al. 2003) substitute of hollow internal organs as ureter, trachea, and digestive tract (Yamanaka et al. 1990 Klemm et al. 2003 Ono et al. 1989) cuff for reconstruction of nerves (Klemm et al. 2003) substitute of duramater (Oster et al. 2003 Damien et al. 2005) substitute of the abdominal wall, skin, subcutaneous tissue, articulation, cartilage, and reinforcement of areas of decreased resistance in the abdominal wall, esophagus, and intestinal tube (Ono et al. 1989) threads (Roberts et al. 1986) and agent for increases in soft tissue, reconstruction of the pelvic... 

Teraska R, Itoh H, Nakafusa Y, Matuso K (1990) Effectiveness of a long intestinal tube in a one-stage operation for obstructing carcinoma of the left colon. Dis Colon Rectum 32 245 248... 

Fig. 7.35. Retrograde intestinal enema study obtained 3 months after intestinal transplantation in 59-year-old man with short-bowel syndrome shows blocked Foley s catheter (open arrowhead) within isolated donor intestinal loop (asterisk) and distal intestinal end-to-side anastomosis (between arrows) between donor ileum and recipient rectum, (d donor, I ileum, / jejunum, r recipient, R rectum.) Annotation intestinal tube (arrowhead)...

Fecal Goliforms. Eecal coliforms are those originating from the intestines of warm-blooded animals. Eecal coliforms can be deterrnined by a multiple-tube procedure, which must be appHed to a positive presumptive test for optimum recovery of fecal coliforms (20). Incubation must be at 44.5 0.2°C for 24 2 h. Gas production during incubation is positive evidence of fecal coliform poUution. 

Endoscopic and surgical feeding tubes can be complicated by erosion of the exit site caused by leakage of gastric or intestinal contents onto the skin. This complication must be... 

The small intestine has the shape of a convoluted tube and represents the major length of the GIT. The small intestine, comprising the duodenum, jejunum, and ileum, has a unique surface structure, making it ideally suited for its primary role of digestion and absorption. The most important structural aspect of the small intestine is the means by which it greatly increases its... 

Figure 1 Increasingly magnified views of intestinal epithelia from cylindrical tube to enterocyte. (From Ref. 76.)...

JH Kou, D Fleisher, GL Amidon. Calculation of the aqueous diffusion layer resistance for absorption in a tube Application to intestinal membrane permeability determination. Pharm Res 8 298-305, 1991. 

The small intestine is assumed to be a cylindrical tube with a surface area of 2kRL, where R is the radius and L is the length of the tube (Fig. 4). The rate at which the drug enters the tube is the product of the inlet concentration, C0, and the volumetric flow rate, Q. The rate at which it exits the tube is the product of the outlet concentration, Cout, and the volumetric flow rate, Q. The absorption flux across the small intestinal membrane, , is the product of the effective permeability, Peff, and concentration, C. The total drug loss by absorption from the... 

Figure 4 Schematic of macroscopic mass balance approach. The small intestine is assumed to be a cylindrical tube with a radius of R and a length of L. The inlet and outlet concentrations are C0 and Cout. The inlet or outlet volumetric flow rate is Q. 

The dispersion model approach was first proposed to simulate dynamic absorption processes [49], The dispersion model assumes that the small intestine can be considered as a uniform tube with constant axial velocity, constant dispersion behavior, and uniform concentration across the tube diameter. Then the absorption of highly soluble drugs in the small intestine can be delineated by the following dispersion model equation ... 

Although skeletal muscle comprises the bulk of muscle tissue in the body, smooth muscle is far more important in terms of homeostasis. Most smooth muscle is found in the walls of tubes and hollow organs. Contraction and relaxation of the smooth muscle in these tissues regulates the movement of substances within them. For example, contraction of the smooth muscle in the wall of a blood vessel narrows the diameter of the vessel and leads to a decrease in the flow of blood through it. Contraction of the smooth muscle in the wall of the stomach exerts pressure on its contents and pushes these substances forward into the small intestine. Smooth muscle functions at a subconscious level and is involuntary. It is innervated by the autonomic nervous system, which regulates its activity. 

Fig. 7.3. The total Loc-I-Gut concept. Left a perfusion system of the duodenal segment. Center a tube system with double balloons which allow a segmental single-pass perfusion of jejunum. Right a perfusion system of the small intestinal stomi.

Kaiampokis, A., Argyrakis, P., Macheras, P., A heterogeneous tube model of intestinal drug absorption based on probabilistic concepts, Pharm. Res. 1999, 16, 1764-1769. 

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