1. Chapter 5 The Path of Food

2. At the end of this unit you should: 1
At the end of this unit you should: 1. Be able to describe what the word ‘digestion’ means. 2. Be able to distinguish between the two types of digestion. 3. Be able to discuss the role of the teeth, tongue and stomach in digestion. 4. Be able to describe mechanical and chemical digestion and the difference between them. 5. Know that digestion involves breaking down large molecules into smaller soluble ones. 6. Be able to describe what happens to food when it is broken down. 7. Be able to describe the role and them importance of enzymes in digestion.

3. absorption
liver
amylase
maltose
appendix
mechanical digestion
bile
nutrients
catalyst
oesophagus
chemical digestion
pancreas
enzymes
rectum
faeces
salivary glands
gall bladder
small intestine
gut flora
soluble
large intestine
stomach

5. Q. What does the term Digestion mean?
1. The breakdown of food into tiny particles

6. Digestion takes place in the digestive system
breaks food down into tiny particles
allows these tiny particles to pass into the blood
is part of how humans feed – that is, human nutrition.

7. Stages in Human Nutrition
Ingestion
Food is taken into the mouth
Food is broken down into smaller soluble pieces
Digestion
The movement of digested food from the alimentary canal into the blood stream
Absorption
Egestion
Removal of undigested /unabsorbed food as faeces

8. Digestive System
3:34mins

9. The digestive system Higher level Ordinary level Mouth Oesophagus
Liver
Stomach
Pancreas
Small intestine
Large intestine
Rectum
Anus

10. Animation digestion
How Does Digestion Work and How Can I Improve Mine? (Animated graphics)

11. Digestion Food is digested in two ways.
2 METHODS
CHEMICAL DIGESTION:
Enzymes
PHYSICAL DIGESTION:
Using the teeth
And muscles

12. Physical digestion occurs when the teeth break down food into smaller pieces.
Physical digestion is also called mechanical digestion.

13. Mouth The mouth: physically digests food by the action of the teeth
chemically digests food by the action of amylase.
Mouth

14. Teeth

15. Your mouth

16. There are four types of teeth
Incisors
cut and slice through food
Canines
grip and tear food
Premolars
chew and crush food
Molars
chew and crush food

17. Cleaning your teeth
Teeth are damaged by bacteria in the mouth. These bacteria convert sugar that you eat into acid. The acid attacks and dissolves your teeth.
Brushing your teeth helps to remove the sticky mixture of sugar and bacteria, called plaque.

18. Oesophagus
The oesophagus is a muscular tube that carries food from the mouth to the stomach.
Oesophagus

19. Chemical digestion occurs when enzymes in the body break down food further.

20. Enzymes- a fun introduction
4:46mins

21. Enzymes
Enzymes are proteins that speed up reactions without being used up in the process.
are similar to catalysts used in chemistry
recall that manganese dioxide is a catalyst used to make oxygen gas

22. Different enzymes Humans produce many different enzymes.
Each enzyme speeds up a different reaction. E.g. different enzymes are responsible for:
healing a cut
making your hair grow
breaking down all the different types of food that you eat.

23. Starch is made up of many units joined in a chain
These units are made of a sugar called Maltose
Starch
Amylase
Maltose
Product
Substrate
Enzyme
Amylase
Maltose
Tell the pupils that amylase acts like a scissors. Amylase enzyme breaks the link in the starch and makes it into a simper sugar called maltose . This results in starch being broken down into maltose
Starch

24. Saliva contains the enzyme amylase.

25. The Enzymes Song

26. Oesophagus
If the stomach produces too much acid, this may rise up the oesophagus and cause a burning sensation. This is called heartburn.

27. Stomach In the stomach: hydrochloric acid kills bacteria
Produce enzymes that break down food.
Churns and physically digests food
Stomach

28. Small intestine In the Small intestine
Produce enzymes that digest food.
tiny digested food particles are absorbed into the bloodstream.
In the first part of the small intestine, a huge range of different enzymes digest all the food that you eat.
In the second part, the tiny digested particles of food are absorbed from the intestine into your bloodstream.
Small intestine

29. Stomach and small intestine
Sometimes enzymes attack the stomach or small intestine. This causes a painful and dangerous condition called ulcers.

30. Liver The liver produces a liquid - bile.
Bile passes into the small intestine & breaks down fats.
Liver
Bile passes into the small intestine where it breaks down large blobs of fat into tiny particles of fat.

31. Liver
Bile passes into the small intestine where it breaks down large blobs of fat into tiny particles of fat. Bile is made in the liver from the remains of broken down red blood cells. Bile is the reason that our waste faeces are brown in colour.

32. Pancreas The pancreas produces digestive enzymes.
They pass into the small intestine where they digest food.
The pancreas also makes a hormone called insulin. Failure to make insulin is called diabetes.
Pancreas
The pancreas makes many enzymes.
These enzyme pass into the small intestine where they digest different types of food.
As well as making enzymes, the pancreas also makes a hormone called insulin. Failure to make insulin is called diabetes.

33. Large intestine
In the large intestine - water is taken back into the bloodstream.
Large intestine

34. Large intestine
If too much water is absorbed from your large intestine, then the waste becomes too solid. This causes constipation.
If too little water is absorbed, the waste is too liquid. This is called diarrhoea.

35. Digestion Song

36. Rectum
The rectum:
stores waste in the form of faeces (semi solid waste).
Rectum

37. Anus
The anus: Faeces pass out of the intestine through the anus.
Anus

38. Investigation - Investigating what happens when food is taken into your body
Equipment:
A pop-sock, pestle and mortar, bin, clear plastic bag, funnel, hydrochloric acid, amylase solution, pepsin, water, a scissors, a sandwich (imagine a sandwich, halved, then halved again, then halved again: this is the size of your sample).
Diagrams:

39. Questions:
1. Working with a partner, match up each body part in the digestion list below with an everyday object in the equipment list that could represent it. (More than one body part can be matched with the equipment list.)
Digestion list: Equipment list:
Intestines Pop-sock
• teeth pestle and mortar
• tongue clear plastic bag
• mouth bin
• toilet funnel
• stomach
• oesophagus

40. Questions
2. Now that you have the equipment list linked to the digestive system and understand the need for the chemicals, plan an investigation to show what happens when food (your sandwich sample) enters your body.
Plan should follow the path of digestion – mouth, oesophagus, stomach, small intestine, large intestine, colon, anus.
3. Where would you find hydrochloric acid in your body?
In the stomach.
4. What does the amylase solution represent?
The enzyme found in our mouths and start of small intestines.

41. 1. Explain what involvement the chemicals had in the
breakdown of your food.
They broke the food molecules into smaller parts.
2. You needed to add water at different stages during the
investigation. Can you link this to real-life experiences?
Make a note of at least two links.
(i) You often need to drink water while eating food as the mouth would be too dry to chew and digest the food otherwise.
(ii) Food would get stuck in the throat if water was not added to the process.

42. 3. Explain how the pestle and mortar relates to your mouth, including references to the chemicals and the water.
The pestle and mortar grinds the food down from large molecules into smaller ones. This is the action by the teeth and tongue. Water and amylase are added. Water helps to lubricate the food and the amylase is the enzyme in our mouths that breaks down carbohydrates.

43. 1. Use the following keywords to describe what digestion is:
Digestion is where food breaks down. It can be mechanically broken down by the teeth, tongue and stomach. It can also be broken down chemically where enzymes are added to the food. As the food is broken down the nutrients are released and absorbed into the bloodstream.
Food breaks down
nutrients
mechanical
chemically