How Gastrointestinal Tract Function?

How Gastrointestinal Tract Function?
An examination of the various mechanisms in the gastrointestinal tract that allow to be ingested, digested, absorbed, and then its residue to be excreted reveals the complexity of the digestion/absorption process. Normal digestion and absorption of nutrients is dependent not only on a healthy alimentary canal but also on an exquisite integration of the digestive system with the nervous system, endocrine system, and circulatory system. An excellent example of this integration of systems is the finely controlled emptying of chyme from the stomach into the small intestine.

The many factors influencing digestion and absorption, including the dispersion and mixing of ingested food, the quantity and composition of gastrointestinal secretions, status of the enterocytes, expanse of intestinal absorptive area and the transit time of intestinal contents must be coordinated so that nourishment of the body can occur while homeostasis of body fluids is maintained. Much of the coordination required is provided by regulatory peptides, some of which are provided by the nervous system as well as by the endocrine cells of the gastrointestinal tract.
How Gastrointestinal Tract Function?

Physiologic Roles of Dietary Fiber

Physiologic Roles of Dietary Fiber
Certain physical properties of fiber such as particle size influence its effect in the gastrointestinal tract. Important characteristics of dietary fiber in relation to its physiologic role include hydration, capacity, adsorptive attraction for organic molecules, cation exchange capacity and fermentability. Fiber exerts its effect throughout the gastrointestinal tract beginning in the mouth. Fiber components that cannot be solubilized (lignin, cellulose and most of the hemicellulose) require increased chewing, thereby stimulating, saliva secretion and serving somewhat as a tooth cleanser.

Often dietary fiber is classified as soluble or insoluble in order to more easily explain its physiological functions. This classification is imprecise, however, because determination of soluble fiber is very difficult and the amount resulting from fiber analysis is influenced by the method used.

The food providing dietary fiber can have a decisive influence in the gastrointestinal tract responses elicited because sources of fiber vary in the relative amount of the different fiber components. For example wheat bran, is primarily hemicellulose, while most fruits, and vegetables contain almost equal quantities of cellulose and pectin. Dietary fiber composition of plant depends on the plant species, the part of the plant consumed (leaf, root, stem) and its maturity. For example lignin is found relatively small amounts in edible plants; its content is highest in fruits with edible seeds, such as strawberries, and in mature root vegetables, such as carrots.
Physiologic Roles of Dietary Fiber