小蔡 asked in 科學生物學 · 2 decades ago

Biology lab question!!

Think about it

1. Saliva contains water (to moisten food), mucus (to lubricate food), salivary amylase (to break down starch), bicarbonate (to buffer acids in food), and antibacterial agents. Why might these last three components be necessary when the stomach is the next destination anyway?

2. Everyone knows different parts of the tongue are especially sensitive to different tastes. But why should we devote tongue space to bitterness?

3. In humans, the uvula hangs as a pendant from the posterior end of the soft palate. During swallowing, it lifts upward and closes off the nasopharynx. Why is this important?

謝謝!!

1 Answer

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  • Yy
    Lv 7
    2 decades ago
    Favorite Answer

    1. Saliva contains water (to moisten food), mucus (to lubricate food), salivary amylase (to break down starch), bicarbonate (to buffer acids in food), and antibacterial agents. Why might these last three components be necessary when the stomach is the next destination anyway?We need water and mucus to moisten food and lubricate food in the esophagus so that the food will not stick in the midway.  We need amylase to digest some fiber to soften the food and make it much easier to swallow.  In addition, most of the digestive enzymes in stomach are proteases not glycosidase.2. Everyone knows different parts of the tongue are especially sensitive to different tastes. But why should we devote tongue space to bitterness?Many poisons taste bitter so that we can avoid eating them.3. In humans, the uvula hangs as a pendant from the posterior end of the soft palate. During swallowing, it lifts upward and closes off the nasopharynx. Why is this important?Since it close the opening, the food will not go to respiratory tract.  If the food gets into trachea, we will be suffocated. 

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