Food passes from our mouths through a tube called the oesophagus into the stomach. There are valves at the top and bottom of the stomach to stop the food coming back out of the top (except when we are being sick) and to stop it leaving the stomach before it has been fully processed. The stomach as a very stretchy bag which is fully of acid. The lining of the stomach is coated in mucous otherwise the acid would destroy the stomach. Food is ground down first by our teeth then by the churning action of the stomach and the acid.

When it leaves the stomach it is sludgy in nature and winds its way along our small intestine by a series of squeezes called peristalsis.

In the small intestine the food becomes alkali as different liquids are added to help digest and breakdown the sludge. Food components get absorbed by the lining of the small intestines as food passes along.

Water gets absorbed from it - mostly in the large intestine.

What's left is brown in colour - mostly due to the excreted pigments and is passed out through a valve at the bottom of the gut called the anus.

Support and movement

We need our skeleton for both support and movement. Our skeleton provides protection for our brains, heart and lungs and the flexibility of our spine allows us to bend and flex.

Muscles and ligaments are attached to the bones which allow us to move. Remember muscles only work one way - they contract. They work in pairs to allow us movement in two directions.

The inside of our bones produces marrow which makes blood and cells for our immune system - no waste of space in your body!

The air that comes in contains a mixture of gases. The very thin membrane lining the lung allows an exchange of gases: oxygen in and carbon dioxide out. The surface needs to be moist, so a large amount of water vapour is also passed into the air.

The oxygen is carried round our bodies in blood in a chemical called haemoglobin which is bright red. The oxygen is used by our muscles to burn fuel (from our food) - just like a fire needs oxygen to burn. The more activity our muscles are doing, the more oxygen they need to operate and so our breathing rate increases.

The heart is responsible for getting the blood to move around our bodies. It a has two loop system, each operated by one half of the heart. The left side of the heart pushes the blood from the heart into the lungs and back to other side of the heart. The right side of the heart pushes this newly charged blood all the way around the body.

Reproduction

All species seek to reproduce themselves and as humans we produce live young after a nine month gestation.

For this we need our reproductive organs: male and female.

Our offspring are helpless for the first few years of their life and rely on a high level of parental care and support to survive. They don’t reach maturity for many years.

Excretion and waste removal

Waste leaves our bodies in several ways.