3.4 organising digestion

• Biologie
• Middelbare school
• havo, vwo
• Leerjaar 2

Welcome everyone 

 Think about...

• Take off your coat, hat/cap off.
• Mobile in the phone bag (on silent).
• Book (laptop) + notebook, pen on the table. Bag on the floor.
• Sit in your own place.
• You can eat and drink in the canteen.
• 5 minutes.

schedule 

• Repetition                    10 min.
• Explanation 3.4         10 min.
• Doing a exercise       15 min      
• Closing                           5 min. 

The 7 nutrients we need

1. Proteins
2. Carbohydrates
3. Fats
4. Water
5. Vitamins
6. Minerals
7. Fibres

What do we need nutrients for? 

1. Growth and repair
2. Energy
3. To stay healthy 

What is digestion

Digestion: Breakdown of food molecules into small food molecules 

When food is digested it is absorbed  

FASES OF DIGESTION:

• INGESTION
• CHEMICAL AND MECHANICAL DIGESTION
• ABSORPTION
• Elemination

Big vs. Small

Big molecules -> Insoluble can not get through the gut wall

Small molecules -> Soluble can get through the gut wall

CHEMICAL DIGESTION:

• BREAKING THE FOOD INTO EVEN SMALLER MOLECULES.
• USING ENZYMES TO BREAK DOWN THE FOOD MOLECULES. 

enzymes 

substrate is broken down

Why chew?

Digestive juices need to digest nutrients

Chewing makes the surface area bigger

Why chew?

Chewing creates a bigger surface area.

bigger surface area = more surface where digestive juices can do their job = more and quicker digestion

surface area of 6 cm2

surface area of 1,5 cm2

together 12 cm2

Learning goals 

• What are the organs of digestion? 
• what is the function of those organs?
• What is peristaltis? 
• What is Emulsification? 

How does our body process the food?

• INGESTION
• MECHANICAL DIGESTION
• CHEMICAL DIGESTION
• ABSORPTION
• Elimination 

Peristaltic movements

• Contractions of muscles 
• esophagus, stomach, duodenum, small intestine, large intestine, rectum
• sphincters (kringspieren) contract behind a bolus of food
• moves food through the digestive tract

ABSORPTION

• Once digestion is complete
• second half small intestine 
• water mainly absorbed in large intestine (colon)

Exercise 

• Draw the organs of the digestive system
• Label the parts
• Add the functions

you can use your book page 76 

INGESTION:

MOVING THE FOOD INTO YOUR MOUTH

INGESTION:

MOVING THE FOOD INTO YOUR MOUTH

MECHANICAL DIGESTION:

• BREAKING THE FOOD INTO SMALLER PIECES.
• THIS IS DONE BY YOUR TEETH
• BITING AND CHEWING

Chemical digestion Step 1

• starts in: the mouth 
• the enzyme: amylase (a carbohydrase)
• the liquid: saliva 
• the nutrient: carbohydrates
• the products: glucose 

The enzymes in your saliva start breaking down the carbohydrate molecules into glucose.

3.4 Organising digestion

What do you remember? 

• What are the nutrients you have to know? 
• Why do we need nutrients? 
• What is digestion?
• What are de different stages of food processing?
• What are enzymes?
• Can you name three enzymes with functions?

Learning goals achieved?  

• What are the organs of digestion? 
• what is the function of those organs?
• What is peristaltis? 
• What is Emulsification? 

The digestive organs

1. liver                        - creates bile
2. gall bladder        - stores bile
3. duodenum          - bile and enzymes from pancreas added
4. appendix              - immunological defense
5. oesophagus          - transports food to stomach
6. stomach               - protein digestion, stomach 
7. pancreas              - creates digestive enzymes
8. small intestine   - digests and absorbs nutrients
9. large intestine    - absorbs water
10. rectum                   - stores faecal matter
11. anus                        - exit hole

Down the tube!

Oesophagus

Peristalsis: moving food down your oesaphagus (gullet)

Why is your stomach rumbling? 

-peristalsis, muscle activity

- mechanical digestion

-Empty stomach and intestines make a louder sound!

In your stomach

Digestive juices are added

• Proteases -> digestion proteins -> amino acids
• Hydrochloric acid -> acid PH, best for the enzymes + acidic environment also kills germs
• Rennin (only babies) makes milk solid, stays in the stomach longer

BILE

• PRODUCED by the lover
• STORED in the gall blatter
• contains emulsifying agents (bile salts)
• contains waste products (bilirubin)
• transporters via a tube to the duodenum

EMULSIFICATION

• by bile salts
• devides larger globules of fat into smaller ones
• increasing surface area for enzyme lipase from pancreas

small           intestine

In your small intestine

2 important liquids added in the first part (the duodenum)

• Pancreatic juice (carbohydrases, proteases and lipases)
• Bile from the liver, stored in the gall bladder
• Bile is alkaline neutralises acid from the stomach
• Bile emulsifies fats, increases surface area of fats lipase enzymes to act upon (emulsification)

In your small intestine

Intestinal juice (carbohydrases, proteases, lipases) Complete digestion of food, made by the wall of the small intestine

Work

• Read pages 76-79
• Make excercises 49 -57

1

2

3

4

5

6

7

8

heart

large intestine

small intestine

stomach

lung

liver

brain

kidney