THE HUMAN DIGESTIVE SYSTEMThe journey of food

OB6

identify and locate the major parts of the digestive system including the mouth, oesophagus, stomach, liver, pancreas, small intestine and large intestine, and know their functions

The Mouth.

Teeth break down food into small pieces.

Salivary glands make saliva.

Chewed food gets mixed with saliva.

Saliva contains enzymes, which start to digest starch to sugar.

Teeth.

Four Types Incisors - Cutting Canine – Grip and

tearing Molars and Pre-

Molars for grinding

Notes on next page

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

Teeth.

Enamel- Hard outer layer

Dentine – Softer interior

Plaque - Bacteria that attack the teeth

Digestion -Breaking food down into smaller pieces

Teeth begin process of breaking down food

Food

Long chains of sugar called

Starch

Saliva contains an ENZYME

(Amylase) Shorter

sugars that start to be digested

Digestive Enzyme Enzymes are biological catalysts

A digestive enzyme is a protein that acts as a catalyst in breaking down food

Starch Amylase(saliva)

Sugar

Digestion

MaltaseAmylase

Long chains of sugar called

Starch

Saliva contains an ENZYME called Amylase- (speeds up the reaction)

Glucose

Shorter sugars that start to be digested

Maltose

Digestion –This also works with other groups for example proteins

Teeth begin process of breaking down food

Eggs

Complicated Protein

ENZYME

Amino Acids etc

Used for growth and repair

To investigate the action of the digestive enzyme (amylase) on starch Add starch and saliva to two test tubes raise

temperature to 37 degrees in a water bath Test one for starch (iodine) Test the other for glucose (Benedict’s solution and heat)

Starch+Saliva Solution

Benedict’s solution

Heat it up

Add Iodine solution

Proves starch has turned to sugar

To investigate the action of the digestive enzyme (amylase) on starch

Substrate

The substrate is the substance that an enzyme acts on.

Starch is the substrate for the enzyme amylase.

Notes on next page

Summary

Substrate Enzyme Product

Starch Amylase Maltose

Experiment

To investigate the action of amylase on starch

Aim

To see if we mix saliva and starch if the starch will turn into sugar

Method To investigate the action of amylase on starch

1. Set up the apparatus as shown in the diagram.

2. Leave the apparatus for 10 minutes (to allow the amylase to act on the starch).

3. Remove a few drops of each solution and mix with a few drops of iodine solution (to test for starch).

TUBE A TUBE B

Starch solution

+Amylase Starch

solution

Water bath at 37°C

Results To investigate the action of amylase on starch

Tube ContentsFinal colour

Conclusion

Tube AStarch and amylase

Red / yellowNo starch present

Tube B Starch Blue / blackStarch present

Conclusion To investigate the action of amylase on starch

In tube A the starch was broken down by the action of the enzyme amylase.

In tube B starch was not broken down as there was no enzyme.

This shows that amylasebreaks down starch.

5 Stages of Nutrition

Ingestion-Eating Digestion-Breaking

up Absorption-Into body

at small intestine Assimilation-Used by

the cells Egestion-Pushed out

The Oesophagus – Food Pipe.

Passes food down to your stomach.

The oesophagus has circular muscles in its wall.

These muscles contract and squeeze in behind the food to push it along.

The Stomach

Muscular bag that holds 2 litres of food.

Secretes Hydrochloric Acid.

Makes digestive juices.

Muscular walls churn the food making sure it’s all mixed.

After 2-3 hours churning it’s a runny liquid. -CHIME

The Small Intestine

Actually 6 m long! Plays important roles

in digestion and

absorption Two important liquids

are added here:Pancreatic juices Bile

Absorption Digested food has to pass into the blood

through the gut wall. Well designed – thin lining, good blood

supply and a VERY LARGE surface area. It has a folded inner lining, millions of tiny

VILLI

Pancreas

Produces digestive enzymes

E.g. amylase Also makes

INSULIN to control sugar in body

Liver

After food has been absorbed into the blood, the food is taken to the liver.

It removes toxins The food dissolved

in plasma is then taken to other parts of the body.

The Large Intestine.

Mainly fibre, dead cell, bacteria and water reach here!

As it moves along here most of the water is absorbed into the blood.

Faeces are stored in the rectum.

Eventually egested out of the anus, roughly 24 –48 hours after eating.