2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

Villi are in the small intestine: they are the surface through which food diffuses into the blood stream. They have thin walls (molecules can pass though easily) and increase surface area, which means the is more surface for diffusions to happen through. On the outside of the villi there are capillaries so it can directly pick up diffused food

2.30 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids

Bile: is produced in the liver and stored in the gall bladder

Enzymes work best in alkaline conditions: food is acidic from being in the stomach. Bile is alkaline so when it is released into the small intestine it allows the enzymes to work (neutralizes stomach acid) Bile also emulsifies fat: give it a larger surface are which means it easier for lipases to work

2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases

2.28 explain how and why food is moved through the gut by peristalsis

The wave like contractions move food through the gut faster and makes it more efficient

The contractions squeeze the food, pushing it down the gut