Grade 5 (age 10-11)

grade 5 Human Body Systems

When you run, you breathe hard and your heart pounds; that is a sign that many organs inside your body are working hard at once. Food you eat is broken into tiny pieces in the digestive system and becomes nutrients, and oxygen in the air you breathe in through your nose enters your body in the lungs of the respiratory system. The heart and blood vessels of the circulatory system carry these nutrients and oxygen in the blood to every part of the body, while bones and muscles hold the body up and move it. Use the slider to switch between the digestive, respiratory, and circulatory systems and see where each organ is and what it does.

The systems of our body

Body systemDigestive system

🫀 Digestive system

①In the mouth, teeth chew food into small pieces and mix it with saliva

②It travels down the oesophagus to the stomach

③In the stomach it mixes with digestive juices and turns soft like porridge

④In the small intestine, nutrients are absorbed into the body

⑤In the large intestine, water is absorbed, and the leftover waste leaves through the anus

Comparing three systems

Digestive · respiratory · circulatory systems compared

Feature	Digestive	Respiratory	Circulatory
Job	Breaks down food and absorbs nutrients	Takes in oxygen and gives out carbon dioxide	Moves blood around the body
Main organs	Mouth, oesophagus, stomach, small intestine, large intestine	Nose, trachea, bronchi, lungs	Heart, blood vessels
Like	A factory that breaks down food	A window that swaps the air	A delivery van touring the whole town
Gives the body	Nutrients	Oxygen	Delivery of oxygen and nutrients

Bones and muscles

🦴 What bones and muscles do

①Bones hold the body up and keep its shape

②The skull protects the brain, and the ribs surround the heart and lungs

③Muscles are attached to bones and move them by shortening and lengthening

④When the muscle on the inside of your arm shortens, the arm bends; when the one on the outside shortens, it straightens

⑤An adult body has about 206 bones and more than 600 muscles

Summary

The path food takes

Mouth → oesophagus → stomach → small intestine → large intestine

Food is broken into small pieces and nutrients are absorbed

The path oxygen takes

Nose → trachea → lungs (oxygen into blood) → heart → blood vessels → whole body

The circulatory system carries the oxygen taken in by the respiratory system around the body

🎯 Key points

①The digestive system breaks down food and absorbs nutrients

②The respiratory system takes in oxygen and gives out carbon dioxide

③The circulatory system carries oxygen and nutrients around the body in the blood

④Bones hold up and protect the body, and muscles move the bones

⑤The body moves healthily only when all these systems work together

Examples and Unit Test

Example 1

Which digestive organ absorbs nutrients from food, and which respiratory organ takes in oxygen?

Food is digested as it passes mouth → oesophagus → stomach → small intestine → large intestine.

Nutrients are mainly absorbed in the small intestine, and oxygen enters the blood in the lungs, part of the respiratory system.

▸ Nutrients are absorbed in the small intestine / oxygen is taken in by the lungs

The large intestine absorbs mostly water rather than nutrients.

Example 2

Using what bones and muscles do, how would you explain why we can bend our arm?

Bones hold up and protect the body, but they cannot move by themselves.

The muscle on the inside of the arm, attached to the bones, shortens and pulls the forearm bone, so the arm bends.

▸ Because muscles shorten and pull on the bones (bones support, muscles move)

Feel the inside of your arm as you bend it and you can feel the muscle bulge and harden.

Unit-test style

Which statement about the structure and work of our body is correct?

①The stomach is the organ that absorbs the most nutrients

②The lungs take in oxygen and give out carbon dioxide

③The heart is the organ that digests food

④Bones shorten by themselves and move the body

⑤The arteries leaving the heart for the body carry oxygen-poor blood

▸ ② The lungs take in oxygen and give out carbon dioxide

The lungs are the respiratory organs that take in oxygen as we breathe in and give out carbon dioxide as we breathe out.

Nutrients are absorbed in the small intestine (①), the heart moves the blood around (③), muscles make the body move (④), and the arteries going out to the body carry oxygen-rich blood (⑤).

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Separating Mixtures

Last updated 2026-10-17