SS1 Second Term Food and Nutrition Lesson Note – The Digestive system

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WEEK: 1

SUBJECT: FOOD AND NUTRITION

TOPIC:  The Digestive system.

CONTENT:  

1. Meaning of Digestion
2. Definition of simple metabolic terms e.g., Enzyme’s absorption.
3. Digestion and absorption of nutrients (Carbohydrates, proteins etc.) in the mouth and esophagus

Sub-topic 1:   MEANING OF DIGESTION

Most of the food taken into the mouth requires some alteration before they can be absorbed into the blood stream. Digestion is the process by which food molecules are broken down into various small substances that can be absorbed into the bloodstream and assimilated into the cells for utilization.  Digestion is mainly a chemical process brought about by the action of numerous enzymes. The whole process of digestion takes place in the alimentary canal.

Digestion and Absorption of Nutrients in the Mouth and Esophagus

1. CARBOHYDRATE

The process of digestion begins in the mouth. The teeth are used to crush large pieces of food. This process is called mastication; mastication exposes the food to action of enzymes. The tongue mixed the food with the saliva which contains ptyalin, an enzyme that breakdown the starch. Saliva performs the following functions 1. It contains mucin which lubricates the food and makes swallow easier.  It provide an alkaline medium necessary for the action of ptyalin, the enzymes that breakdown carbohydrate.  Digestion of starch starts from the mouth by the action of the saliva amylase otherwise known as ptyalin. The saliva provides an alkali medium that facilitates the action of ptyalin. This breakdown the complex carbohydrates into simple carbohydrates called maltose. No chemical reaction happens to protein and fat in the mouth.

Sub topic 2: Digestion of Protein nutrients in the stomach

Food passes into the stomach through the esophagus after mixing in the mouth. In the stomach, gastric glands secrete gastric juice, a mixture of water, enzymes, and hydrochloric acid that acts primarily on protein foods. It is as a result of present of hydrochloric acid that gastric juice is acidic. The acidic medium in the stomach (i) Stop the action of ptyalin (ii) Stop the growth and destroys the bacteria that comes along with the food from the mouth. Mucus is secreted in the stomach to prevent the stomach wall from the action the gastric juice and hydrochloric acid (HCL).

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