Digestion

Human Biology

Main Organs Reproduction Digestion Circulation Breathing and the respiratory system

Digestion Food and diet:
Summary Table of nutrients Running Heart Disease Respiration

Food enters the body at the mouth

The food that we eat contains lots of nutrients. Nutrients are useful chemicals needed by our body.

In order to release the nutrients from the food the food needs to be broken down into smaller pieces.
This breaking down of food is called digestion. and is helped by special chemicals called enzymes.

After the food is digested the nutrients are absorbed into the blood

Most digestion takes place in the small intestine.

Unwanted food is removed from the body through the anus.

Summary showing the order of events:

Process:	Ingestion	Digestion	Absorption	Excretion
Description:	Taking in food	Breaking down food using enzymes	Nutrients entering the blood	Removal of waste products
Location:	Mouth	Stomach and Intestines	Small intestine	Kidneys

Diet
A diet is the type food we eat.

A balanced diet is selecting sensible foods so we have the right proportion of all the nutrients we need.

The table below shows the nutrients that need to be present in a balanced diet

Nutrient	Why the nutrient is needed	Example foods
Carbohydrate	The main source of ENERGY for movement, warmth, cell repair, growth	Sugar and starch eg potato, bread,
Fat	Energy. Easier for our body to store than carbohydrate. Helps insulate the body from cold.	Dairy food (milk, cheese), oils
Protein	Body building. eg muscle growth, Repairing and building cells.	Meat, soya, cheese
Vitamins	Needed in small amounts to keep our body healthy eg Carrot (vit A) Marmite, bread (vit .B), Fresh fruit (vit C) Liver (vit D), Green veg. (vit.E). Vitamin. C helps stop a disease called scurvy	Fresh fruit and vegetables.
Minerals	Needed to keep us healthy eg calcium (strong bones): a lack of calcium can cause rickets. iron (making blood): a lack of iron can cause anaemia	Milk and cheese (calcium); vegetables (eg spinach is rich in iron)
Dietary fibre^*	Helps digestion. Helps reduce the risk of heart disease by lowering cholesterol.	Brown bread, vegetables, cereal
Water^*	Water is the main part of all living cells. Our body is 75% water.	drinks , fruit

* strictly speaking water and fibre are NOT nutrients.

Fibre helps us to digest food .

We lose water all the time (eg by sweating and breathing out water vapour) and it needs to be replaced. A lack of water will make us ill far quicker than lack of food.

Milk is an important food as it contains most nutrients. It is rich in calcium so is an important food for growing children, however it does not provide a balanced diet. Other foods are needed to provide those nutrients not in milk.

What happens when we run

Our muscles move more and so need more food and oxygen from the blood.

This causes the following changes in our body:

Our heart pumps quicker to get the blood to the muscles quicker.
We breath faster to transfer more oxygen to the blood
We sweat more. As the sweat evaporates it helps cool the body and remove excess heat.

Heart disease
Heart disease can be caused by too much fat which clogs the arteries reducing the flow of blood to the heart. Exercise helps reduce the risk by speeding the flow up blood up which helps clear the arteries.

How to help reduce the risk of heart disease: