The digestive systemIB MYP Sciences: Subtopic test

1. 1
   A boy in Istanbul eats a lunch of bread, cheese and olives. Over the next few hours the food travels through his alimentary canal, and digestive juices are added to it by several organs.

   (a)

   Which row shows the correct order in which food passes through the alimentary canal?

   [1 mark]

   • AMouth, stomach, oesophagus, small intestine, large intestine
   • BMouth, oesophagus, small intestine, stomach, large intestine
   • CMouth, oesophagus, stomach, large intestine, small intestine
   • DMouth, oesophagus, stomach, small intestine, large intestine

   (b)

   Which organ produces bile?

   [1 mark]

   • ALiver
   • BGall bladder
   • CPancreas
   • DStomach

   (c)

   Explain the functions of bile in digestion.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Singapore swallows a mouthful of bread. In the mouth the bread is chewed and mixed with saliva, and it is then swallowed as a soft ball of food.

   (a)

   Which of these is an example of chemical digestion?

   [1 mark]

   • ATeeth cutting bread into smaller pieces
   • BSalivary amylase breaking down starch into maltose
   • CThe stomach wall churning the food
   • DMuscles pushing the food along the oesophagus

   (b)

   What is the name of the wave of muscle contractions that pushes the soft ball of food down the oesophagus?

   [1 mark]

   • AAbsorption
   • BAssimilation
   • CPeristalsis
   • DEmulsification

   (c)

   Explain why chewing food helps chemical digestion.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The small intestine is about 6 m long and its inner lining is covered with millions of tiny finger-like projections called villi. A patient with coeliac disease has villi that have become flattened, and she absorbs much less digested food into her blood than a healthy person.

   (a)

   Explain how villi are adapted to absorb digested food efficiently.

   [3 marks]

   (b)

   Explain why the patient with flattened villi loses weight and feels tired.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Surgeons in Mexico City treat some patients with severe obesity using a gastric sleeve operation, which removes about 80% of the stomach. After the operation, patients can eat only small meals. In a related class activity, a student models the effect of breaking up food by timing how long an antacid tablet takes to dissolve in warm water. He used three trials for each. A whole tablet took a mean of 210 seconds to dissolve and a crushed tablet of the same mass took a mean of 45 seconds.

   (a)

   Evaluate the student's model as a way of showing why chewing and churning food help digestion.

   [6 marks]

   (b)

   Discuss and evaluate the use of gastric sleeve surgery to treat severe obesity.

   [6 marks]

   Total for question 4: 12 marks

End of questions