Science notes, unit 2

Humans

Textbook Science Year 5 (DLP), pages 19–48

What this chapter covers

You can name the main parts of the human skeletal system and explain what each part does (2.1.1)
You can show where the main joints of the body are (2.1.2)
You can explain what joints do and why we need them (2.1.3)
You can explain why the skeletal system is important (2.1.4)
You can name the main parts of the blood circulatory system and state what each part does (2.2.1)
You can describe the pathway of blood rich in oxygen and blood rich in carbon dioxide (2.2.2)
You can explain why the blood circulatory system is important (2.2.3)
You can sketch the blood circulatory pathway (2.2.4)
You can explain how the skeletal, respiratory, digestive and blood circulatory systems depend on one another (2.3.1)
You can explain why we must take care of every system and how to protect each one (2.3.2, 2.3.3)

Your body is not just a heap of parts. It is made up of systems, and each system has its own job. In this unit you will study the skeletal system and the blood circulatory system, then see how the systems of the body depend on one another.

2.1The human skeletal system

The human skeletal system is made up of all the bones in the body.

A worm has no bones, so it cannot stand up like a human. Without bones, we would only be able to writhe and wriggle.

Main parts and their functions

Human skeleton with the skull, rib, backbone, hand bone and leg bone labelled — The human skeletal system.

Main part	What it does
Skull	Protects the brain from injury
Backbone	Supports the body, so we can stand upright
Ribs	Protect the internal organs such as the lungs and heart
Hand bones and leg bones	Give support and allow movement

Back view of the backbone — The backbone supports the body.

Rib cage covering the lungs, heart, liver and stomach — The ribs protect the lungs and heart.

Did you know? There are many small bones in your hand and fingers. Press them and feel! Many small bones let your fingers do fine work, like writing.

Joints

A joint is a place where two or more bones are joined together.

The two bones of the knee meet at the knee joint. Bones connect to each other at joints.

Skeleton with circles at the neck, shoulder, backbone, elbow, wrist, hip, knee and ankle — Positions of joints in the human body: neck, shoulder, elbow, wrist, backbone, hip, knee and ankle.

Why do we need joints? Ravi's arm is covered with a bandage, so his bones cannot move and he cannot bend his arm. This is what it would be like if we had no joints.

A boy with a bandaged arm who cannot bend it — An arm that cannot bend shows what life would be like without joints.

Joints allow movement and flexibility of the body.

Joint	Movement it makes possible
Neck	Turning and rotating the head
Shoulders, hands and backbone	Movement of the upper body
Shoulders	Arms move back and forth, to the sides or in circles
Knees and hips	Legs bend and straighten

A boy turning his head from side to side and nodding — The neck joint lets the head turn and rotate.

A boy moving his arms up and bending sideways — Shoulder and backbone joints move the upper body.

Legs bending and straightening at the knee — Knee and hip joints let the legs bend and straighten.

Why the skeletal system is important

It supports the body, so we can stand and sit upright.
It lets the body move, with the help of the joints.
It protects soft organs: the skull protects the brain, and the ribs protect the heart and lungs.

Do not say that the skull "supports" the brain. The skull protects the brain. The backbone is the part that supports the body.

State the function of the ribs and give one organ they protect.

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The ribs protect the internal organs, for example the heart or the lungs.

2.2The human blood circulatory system

The blood circulatory system transports oxygen, nutrients, water and waste products such as carbon dioxide around the body. Its four main parts are the heart, blood vessels, blood and lungs.

Part	Function
Heart	An organ that pumps blood to the lungs and to the whole body
Blood vessels	Tubes that allow blood to flow and transport blood to the whole body
Blood	Transports oxygen, nutrients, water and waste products
Lungs	Organs where oxygen and carbon dioxide are exchanged

Cross section of the heart with the left side and right side labelled — The heart has two sides. The left side pumps blood rich in oxygen to the whole body. The right side pumps blood rich in carbon dioxide to the lungs.

A blood vessel cut open to show blood cells inside — A blood vessel is a tube. Blood flows through it.

Did you know? The textbook shows blood rich in oxygen in red and blood rich in carbon dioxide in blue.

The blood circulatory pathway

Type of blood	Pathway
Blood rich in oxygen	Lungs → heart → human body
Blood rich in carbon dioxide	Human body → heart → lungs

When we inhale, air rich in oxygen enters the lungs and the oxygen is absorbed into the blood vessels.
The blood is now rich in oxygen. The heart pumps it to the whole body.
The body uses up the oxygen and produces carbon dioxide, which is absorbed into the blood.
The blood is now rich in carbon dioxide. It is transported to the heart.
The heart pumps it to the lungs. When we exhale, carbon dioxide leaves the lungs.

This happens again and again every time we breathe. That is why the blood circulatory system is closely related to the respiratory system.

Air entering the trachea and lungs of a boy as he breathes in — Air that we inhale enters the trachea and the lungs.

Do not mix up the two pathways. Oxygen-rich blood goes from the lungs to the heart and then to the body. Carbon-dioxide-rich blood goes from the body to the heart and then to the lungs.

Why the blood circulatory system is important

It transports oxygen, nutrients and water to the whole body.
It transports carbon dioxide and other waste products out of the body (to the lungs, and to the kidneys, which are excretory organs).

Without this system, the body could not carry out life processes. Nutrients that are absorbed from the intestines are carried by the blood to the heart, and then pumped to the whole body.

Which side of the heart pumps blood rich in carbon dioxide, and where does it pump it?

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The right side of the heart pumps it to the lungs.

2.3Systems working together

The body has many systems, for example the skeletal, respiratory, digestive and blood circulatory systems. They cannot function independently. If one system fails, the others are affected too.

System	How it depends on the blood circulatory system	How it helps the others
Respiratory	Blood carries the oxygen to the whole body and carries carbon dioxide away	Takes in oxygen for the blood
Skeletal	Blood brings oxygen and nutrients so bones can grow	Protects the lungs and heart
Digestive	Blood transports oxygen to it	Supplies nutrients to organs such as the heart

When one system is disrupted

Choking on food

Food is stuck at the oesophagus. The digestive system is disrupted. The food also blocks air from entering the trachea, so the respiratory system is disrupted and breathing becomes difficult.

Food stuck in the oesophagus next to the trachea and lungs — Food stuck in the oesophagus blocks air from entering the trachea.

A fractured bone

A fractured hand bone affects the skeletal system. The arm also becomes swollen because blood flow in the blood circulatory system is disrupted.

Protecting the systems of the body

Eating too much food with a lot of fat can build up cholesterol plaque in the blood vessels. The plaque makes the blood vessels narrow, so the heart has to work harder to pump blood.

The heart and a blood vessel narrowed by cholesterol plaque — Cholesterol plaque narrows a blood vessel.

System	How to protect it
Skeletal	Eat food rich in calcium (such as milk); do physical activities; wear protective gear and seat belts
Respiratory	Avoid cigarettes; live in a clean environment; wash hands often
Blood circulatory	Eat less food high in fat and sugar; exercise regularly
Digestive	Eat food rich in fibre; drink enough water

A boy wearing a helmet on a bicycle and a man wearing a seat belt in a car — Helmets and seat belts protect the skeletal system.

Did you know? Smoking causes respiratory diseases such as asthma, bronchitis and lung cancer. Fruit, vegetables and whole grains give fibre, which helps defecation.

Each habit protects one main system. Do not write "drink enough water" for the skeletal system. It is for the digestive system. Calcium is for bones.

Name two other systems that are affected when a person chokes on food.

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The digestive system (the oesophagus is blocked) and the respiratory system (air cannot enter the trachea).

Pictures: Science Year 5 (DLP) textbook, pp. 19–48 (skeleton p. 20, backbone and ribs p. 21, joints p. 22, bandage p. 23, joint movements pp. 24–25, heart p. 28, blood vessel p. 29, pathway p. 30, breathing p. 31, choking p. 36, plaque p. 38, protective gear p. 40).

Summary

Topic	Key points
Skeleton	Skull protects the brain; backbone supports; ribs protect organs; hand and leg bones support and move the body
Joints	Where two or more bones meet; allow movement and flexibility
Circulatory parts	Heart pumps; blood vessels carry; blood transports; lungs exchange gases
Pathway	Oxygen-rich: lungs → heart → body. Carbon-dioxide-rich: body → heart → lungs
Importance	Transports oxygen, nutrients and water; removes carbon dioxide and wastes
Systems	Depend on one another; take care of all of them