The digestive system

What is digestion?

Digestion is the process by which your body breaks down the food you eat into smaller, simpler substances that can be absorbed into the blood and used for energy, growth, and repair.

OR

To convert large insoluble food molecules into smaller soluble ones

Why do we need to?

Small food molecules can pass through the walls of the small intestine and then dissolve into the blood stream. Large food molecules cant do this

Mechanical digestion

Digestion begins in the mouth where food is broken down by the teeth. This is called mechanical breakdown. The small parts of food are mixed with saliva and swallowed

Passage

1. Mouth

1. Oesophagus

2. Stomach

3. Small intestine

4. Large intestine

5. Anus

The stomach

After food is swallowed it enters the stomach which is basically a muscular bag filled with hydrochloric acide. So food enters the stomach from the gullet.

Two things happen to food in the stomach

• microbes are destroyed

• The chemical breakdown of food begins

The small intestine

From the stomach, food enters the small intestine where digestion is completed and the small digested food molecules are absorbed into the bloodstream

Large intestine

After the small intestine, the remains of any undigested food travel to the large intestine. All that is left of the food is water and waste material. The water is valuable and so it is absorbed into the large intestine into the blood stream.

Waste material

It cannot be digested or used by the body. This undigested waste travels to the rectum where it is stored until leaving the Body through the anus

Digestive enzymes

The chemicals that break large insoluble food molecules into smaller soluble molecules

Different types of digestive enzymes

The chemicals that break large insoluble food molecules into smaller soluble molecules. They are classified by the type of food that they affect, so there are three main types: carbohydrase, protease, lipase

Carbohydrase

Breaks carbohydrate into smaller sugars

Protease

Breaks protein into amino acids

Lipase

Breaks fat into fatty acids and glycerol

Enzymes and carbohydrate digestion

Carbohydrates are chains of identical sugar molecules.

The digestive enzymes called carbohydrase break the chemical bonds between the individual sugar molecules in each carbohydrate chain

Enzymes and protein digestion

Proteins are made up of amino acids.

Proteins are digested enzymes called proteases. These enzymes work in an acidic environment to break the proteins into smaller amino acids

Enzymes and fat digestion

Fats are digested in two stages

Firstly bile (released by the gall bladder) allows the fat to “mix” with water by breaking the fat into smaller droplets. This is called emulsification.

Secondly, the digestive enzyme lipase breaks each fat molecule into the smaller glycerol fatty acid molecules.

Carbohydrate

A nutrient in food that provides energy

Enzyme

A chemical that helps digestion breaking large molecules into smaller ones.

Fat

A nutrient in food that provides a store of energy

Large intestine

The organ where water is removed from undigested food

Minerals

Compounds in food that provides the elements needed in small amounts for a healthy diet

Protein

Needed for growth and repair

Vitamins

Substances found in food that are needed in small amounts for health.

Stomach

– The organ where food is mixed with acid and enzymes.

Small intestine

The organ where digestion is completed and digested food molecules are absorbed.