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Systems that each do one job and all depend on the others

The circulatory system moves blood, the respiratory system exchanges gases, the digestive system breaks food into what can be absorbed, the skeletal and muscular systems move and protect, and the nervous system carries signals. Each has one job and none works alone.

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In beta. This lesson was written for Hone and has not yet been checked by a state certification officer. Practice material, not professional advice. What that means.

What it is for

A pupil asked 'where does the oxygen in your blood come from' has to cross two systems in one answer, and that is the point of teaching systems rather than parts. Naming the organ is recall; tracing the path is understanding, and the examination asks for the path.

How to think about it

For any question, name the system, then the organ, then the job. Then trace the path of one thing, oxygen or a mouthful of food, through every system it touches. The handovers between systems are where the questions are set.

Worked example

Oxygen enters at the lungs and is handed to the blood
The handover point between respiratory and circulatory.
The heart pumps that blood to every cell, where the oxygen is used in respiration
Circulatory to cellular, and back to the first lesson on this road.
Digestion breaks food down until it is small enough to cross into the blood
Which is why the small intestine, not the stomach, is where most absorption happens.
The nervous system carries the signals that make the muscles move the skeleton
Three systems in one action.

Your turn

Name the system that carries oxygen from the lungs to the cells.

The  system carries oxygen around the body

The trap

Placing digestion's absorption in the stomach. The stomach breaks food down; most of what is absorbed crosses in the small intestine, and the difference is regularly examined.

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