Small intestine function

Madge DS. 1977. Effects of trichlorphenoxyacetic acid and chlorodioxins on small intestinal function. Gen Pharmacol 8 319-324. 

GLUT5, present in the small intestine, functions primarily as a fructose transporter. 

Levin RJ. Assessing small Intestinal function in health and disease in vivo and in vitro. Scand J Gastroenterol Suppl 1982 74 31-51. 

Dietary fiber is only one of several possible pharmacologically active substances found in foods, and present in high concentrations in leguminous seeds which may be responsible for the different rates of digestion and blood glucose responses of different meals. Enzyme inhibitors, lectins and saponins are other so called antinutritional factors, also associated with dietary fiber which are able to alter small intestinal function (48). The gastrointestinal tract evolved to deal with these constituents in foods so that while toxic in large amounts (as in uncooked beans) small amounts may have beneficial effects. 

Pageot, L.-P, Perreault, N., Basora, N., Francoeur, C., Magny, P, and Beaulieu, J.-F. 2000. Human cell models to study small intestinal functions recapitulation of the crypt-villus axis. 

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... 

AQP10 has only been identified in the small intestine so far and is thought to play a role in hormonal secretion. AQP11 is expressed in kidney, liver, testis and brain, but no function has been found so far. AQP12 has been identified in pancreatic acinar cells, where it is thought to facilitate the release of digestive enzymes into the pancreatic duct. 

A wide diversity of herbal remedies have purported abilities to stimulate defense functions. Complexes of carbohydrate and lignin, which are present in some herbs, modulate enteric immune functions (Kiyohara et al, 2000), and the changes in cytokine secretion (Matsumoto and Yamada, 2000) can trigger systemic responses. The polysaccharides present in other herbal medicines augment production of immunoglobulin (Ig) A by the Peyer s patches in the small intestine (Sakushima et al, 1997 Yu et al, 1998). The responses of the enteric immune system to lectins are variable (Pusztai 1993), and can elicit systemic responses (Lavelle et al, 2000). Other phytochemicals provide protection by inducing detoxification pathways in mucosal cells (Williamson et al, 1998). 

Saponins and phenolics also have anti-microbial properties (Chung et ah, 1998) and have been associated with reduced rumen functions (Klita et al., 1996 Reed, 1995), thereby limiting the nutrient quality of forages. Also, carbohydrate complexes with hgnins and other compounds reduce carbohydrate utilization by rumen bacteria (Cornu et al., 1994). The influence of such anti-microbials on rumen functions can affect small intestine characteristics by altering nutrient concentrations (Barry and McNabb, 1999). 

Levodopa, a dopamine precursor, is the most effective agent for PD. Patients experience a 40% to 50% improvement in motor function. It is absorbed in the small intestine and peaks in the plasma in 30 to 120 minutes. A stomach with excess acid, food, or anticholinergic medications will delay gastric emptying time and decrease the amount of levodopa absorbed. Antacids decrease stomach acidity and improve levodopa absorption. Levodopa requires active transport by a large, neutral amino acid transporter protein from the small intestine into the plasma and from the plasma across the blood-brain barrier into the brain (Fig. 29-2). Levodopa competes with other amino acids, such as those contained in food, for this transport mechanism. Thus, in advanced disease, adjusting the timing of protein-rich meals in relationship to levodopa doses may be helpful. Levodopa also binds to iron supplements and administration of these should be spaced by at least 2 hours from the levodopa dose.1,8,16,25... 

Letsch A, Keilholz U, Schadendorf D, et al. Functional CCR9 expression is associated with small intestinal metastasis. J Invest Derm 2004 122 685-690. 

Figure 6.1 Acids and bases exist in the human body and are necessary for its proper function, including the function of the digestion process. When food is swallowed, it is attacked by stomach acids. The stomach acids need to be neutralized before food can continue down the digestive tract. A hormone called secretin monitors the pH balance in the small intestine and sends chemical signals to other parts of the body, thereby regulating pH balance.

The third mucosal layer is that lining the entire length of the small intestine and which represents a continuous sheet of epithelial cells. These epithelial cells (or enterocytes) are columnar in shape, and the luminal cell membrane, upon which the microvilli reside, is called the apical cell membrane. Opposite this membrane is the basal (or basolateral) plasma membrane, which is separated from the lamina propria by a basement membrane. A sketch of this cell is shown in Fig. 5. The primary function of the villi is absorption. 

Jackson, M. J. Tai, C.-Y., Morphological correlates of weak electrolyte transport in the small intestine, in Dinno, M. A. (ed.), Structure and Function in Epithelia and Membrane Biophysics, Alan R. Liss, New York, 1981, pp. 83-96. 

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 pancreas is an exocrine gland and an endocrine gland. The exocrine tissue produces a bicarbonate solution and digestive enzymes. These substances are transported to the small intestine where they play a role in the chemical digestion of food. These functions are fully discussed in Chapter 18 on the digestive system. 

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