Brent Cornell

    
The human intestines function to complete the process of digestion and absorb digested products into the bloodstream

• The small intestine absorbs usable food substances (i.e. nutrients – monosaccharides, amino acids, fatty acids, vitamins, etc.)
• The large intestine absorbs water and dissolved minerals (i.e. ions) from the indigestible food residues

Dietary Fibre

Dietary fibre, or roughage, is the indigestible portion of food derived principally from plants and fungi (cellulose, chitin, etc.)

• Humans lack the necessary enzymes to break down certain plant matter (e.g. lack cellulase required to digest cellulose)
• Certain herbivores (ruminants) possess helpful bacteria in the digestive tract that can break down indigestible plant matter

The rate of transit of materials through the large intestine is positively correlated with their fibre content:

• Roughage provides bulk in the intestines to help keep materials moving through the gut
• Roughage also absorbs water, which keeps bowel movements soft and easy to pass

There are several health benefits associated with diets rich in dietary fibre:

• It reduces the frequency of constipation and lowers the risk of colon and rectal cancer
• It lowers blood cholesterol and regulates blood sugar levels (by slowing the rate of absorption)
• It aids in weight management (contributes few calories despite consisting of a large volume of ingested material)

Egestion

Materials that are not absorbed by the small and large intestines are ultimately egested from the body as faeces

• A large portion of human faeces consists of dietary fibre, such as cellulose and lignin
• Also present in faeces are the remains of intestinal epithelial cells, bile pigments and human flora (intestinal bacteria)

Summary of egested materials:

• Bile pigments
• Epithelial cells
• Lignin
• Cellulose
• Human flora (bacteria)

Mnemonic:  BELCH