the digestive system

Question 1

where is the gut

Answer 1

coiled up in the abdomen (it is very long 8m in adults)

Question 2

what is the first part of the small intestine called

Answer 2

the duodenum

Question 3

what do the mouth, stomach, and duodenum use to break down food

Answer 3

digestive enzymes

Question 4

where are the digestive enzymes made

Answer 4

in the gut wall or in the glands like the pancreas

Question 5

what is the last part of the small intestine

Answer 5

the ileum

Question 6

what happens in the ileum

Answer 6

digested food is absorbed

Question 7

what does the large intestine do

Answer 7

it absorbs water and stores waste (faeces)

Question 8

the 3 food classes have 3 types of enzymes to break them down. what are they

Answer 8

1 Carbs are digested by carbohydrases
2 Proteins are digested by proteases
3 Lipids are digested by lipases

Question 9

look in your notes for further explanation on the enzymes

Answer 9

have a good study session

Question 10

what happens to food when it enters the mouth

Answer 10

1 the food gets chewed (mechanical digestion)

2 saliva moistens the food and contains amylase which breaks down starch (chemical digestion)

3 the chewed up lump (bolus) goes through the oesophagus to the stomach

Question 11

what happens to food in the stomach

Answer 11

1 food is held there for hours

2 the walls secrete hydrochloric acid to kill bacteria (prevent food poisoning)

3 the protease pepsin is also secreted unto the food to digest the proteins

4 the muscles in the wall of the stomach churn up the food (mechanical digestion)

5 the sphincter muscle hold the food in the stomach and then relaxes to let it into the small intestine

Question 12

what adapts pepsin so well to working in the stomach

Answer 12

it optimum ph is very low (2) because the stomach is acidic

Question 13

what happens in the first part of the small intestine (duodenum)

Answer 13

1 enzymes made by the pancreas (pancreatic juice) digest the starch, proteins and lipids in the food

2 the liver also makes bile which passes down the bile duct unto food

3 the food continues to go down the intestine till all the digestible parts are broken down.

4 food then goes down to the ileum to be absorbed

Question 14

what is bile

Answer 14

1 bile is a green liquid

2 it is stored in the gall bladder and passes down the bile duct unto food

3 bile has no enzymes

it turns large lipids into small droplets giving them a better surface area for the lipase enzyme to act on them (this is called emulsification)

Question 15

what is another role that bile and pancreatic juice have

Answer 15

both of them are alkaline so they neutralize half digested acidic food from the stomach

Question 16

what happens in the second part of the small intestine (the ileum)

Answer 16

this is where digested food is absorbed into the blood

Question 17

what adapts the ileum so well to this role

Answer 17

1 the length of the intestine and the folds in its lining helps give a better surface area for absorption (diffusion, active transport)
2 the greatest increase in surface area is the villi

Question 18

what are the villi

Answer 18

little projections from the lining of the ileum

Question 19

what adaptations do the villi have

Answer 19

1 each one is 1-2mm long and there are millions of them making a surface area of 300m²

2 surface cells of the villi have microvilli which increase surface area

3 the villi have blood capillaries in them, most digested food enters these

4 the villi have a tube in its middle called the lacteal which takes fat digestion products and fat droplets

5 the villus has a surface made of a layer of cells (epithelium) meaning it has a short distance for diffusion

Question 20

what does the lacteal do

Answer 20

the lacteal transports lymph which eventually get drained into the blood. the lacteal is a part of the lymphatic system

Question 21

what is the epithelium cells adaptation

Answer 21

they have lots of mitochondria giving a lot of energy for active transport