a) Make sure that the students can distinguish between mechanical and chemical digestion.
b) What role does HCL play with regard to protein digestion and bacteria?
c) What are the roles of the small and large intestines?
he first step of digestion, the cephalic phase, takes place before ingesting food. In this phase, the body prepares itself to digest any food consumed in the near future. Shortly afterwards (hopefully!) biting and chewing take place in order to reduce the food into more easily digested pieces, which is a mechanical process, as well as moistening of the food with saliva, a chemical process.
When swallowed, the food arrives at the stomach for further digestion. The stomach contains several compounds, one of which is hydrochloric acid (HCl), which is, "extremely important for digestion because it starts to denature proteins" (Tucker, 94). This process is pivotal because proteins cannot be digested as they are ingested. They must be broken down before they can be absorbed into the body. In addition, it serves as a neutralizer for foreign bacteria that attempt to infect the body.
As the stomach digests, it slowly releases the dissolving food into the small intestine, the longest piece of the tract. In the small intestine, the food is broken down into small molecules which the body can absorb right through the walls of the intestine and into the bloodstream and lymph system. The liver then releases those nutrients into the bloodstream to travel throughout the rest of the body, and filter poisonous cells out.
Next, the large intestine absorbs the rest of the water and stores the waste until it can be disposed of.
Sheila Tucker, B.E. Pruitt, Jane J. Stein, Benjamin Cummings, Joan Salge Blake, Janice Thompson, Melinda Manore. Nutrition, Health, and Wellness: An Applied Approach VitalSource eBook For DeVry University. Pearson Learning Solutions. 2010.
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