© boardworks ltd 2004 1 of 53 the heart and circulatory system ks4 biology

© Boardworks Ltd 20041 of 53

The Heart and Circulatory System

KS4 Biology


The heart and circulatory system

How are substances transported?

The heart: structure and function

The action in motion

The valves: structure and function

Multiple choice section

Contents


The next organ system we will be considering can be known by two names…..

Blood system Circulatory system

The circulatory system is made of two parts:

1. The heart2. The blood vessels

How are substances transported in our bodies?


One of the substances that the circulatory system transports are respiratory gases.

For example, the oxygen that the body needs, must be taken to the cells and the carbon dioxide waste gas must be taken away from the cells.

What we use in the air


As these gases are carried by the blood, it means that in terms of the presence of gas, we have two types of blood.

blood low in oxygen

deoxygenated

blood high in oxygen

oxygenated

At all times these two types of blood cannot mix. Why do you think this is?

Dissolved gases in blood


This section of the system including the right side of the heart, deals with the deoxygenated blood.

This section of the system including the left side of the heart, deals with the oxygenated blood.

Lungs

Body cells

Because of this our circulatory system is in two parts. It is in fact called a double circulatory system.

A double circulatory system


The human circulatory system








Contents


In this unit we are going to focus on the heart..

This is the pump at the centre of the circulatory system.

Not all living organisms have hearts. Also, the shape of the heart can change, depending on what species you look at.

The Heart



The heart is made almost entirely of muscle. It is unlike any other muscle in your body because it never tires. And even though it is full of blood it still needs it own blood supply. Oxygenated blood is carried to the heart by the coronary arteries.

Each side of the heart has two chambers.

1. An top chamber or atrium and2. A bottom chamber or ventricle

Each of these chambers has its own function. Look at the diagram on the next slide to see what that is.

One big muscle


Diagrammatical representation








Contents


Besides the chambers there is also another very important part of the heart – the valves.

These valves are found between the top and bottom chambers on both sides of the heart.

blood

valve

These valves are rather like doors that only open in one direction.



As the atrium fills with blood, the valves are closed.

When the atrium contracts and squeeze the blood, the valves are pushed open.

These valves are connected to the side wall of the heart by tough tendons.

These tendons allow the valves to close but not invert.

Valves in action


valve

tendon

wall of ventricle

These tendons can be compared to an arm holding onto the handle of a door.

Tendon holding a valve


The arm bends as the door is opened.

When the door is closed the arm is fully extended.

It would be impossible for the door to open in the other direction without the person moving with it.

The tendon (represented by the arm) is held in a fixed position and therefore the valve (door) can only open in one direction.

Analogy of a valve


The blood will naturally push against the valve.

However, the valves remain firmly shut.

In this way, the blood can be moved from chamber to chamber quite efficiently.

The valves prevent the blood from moving in the wrong direction.

Preventing backflow


we also find valves here ...and here!

These extra valves stop the blood from re-entering the heart when it is pumped from the ventricles.

More valves


When the blood knocks against the second set of heart valves, it makes a ‘dub’ like sound.

valve

ventricle

artery The blood ‘slaps’ against the valve and then passes along the artery.

These two sounds – lub and dub – are actually what we hear as our heartbeat. So our heartbeat is in fact the sound of the valves opening and closing.

When the blood knocks against the first heart valves, it makes a ‘lub’ like sound.

Lub - dub


The heart’s main valves








Contents


Now that we can name all of the parts of the heart it is time to see how they work to push blood around the body.

The heart pumps blood when its muscle contracts. As the muscle contracts the chamber gets smaller and squeeze the blood out.

The two sides of the heart work together. The atria contract and relax at the same time, as do the ventricles.

The next two slides describe what occurs inside the heart during one heart cycle.



blood from the body

blood from the lungs

1. The heart beat begins when the heart muscles relax and blood flows into the atria.

2. The atria then contract and the valves open to allow blood into the ventricles.



The staged cycle then repeats itself.

3. The ventricles contract forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood.



Do you notice anything different about the two sides of the heart?

Well, the left ventricle wall is clearly thicker than the right ventricle wall.

Why is this?

To answer this question, think about where the blood is going when it leaves the right and left ventricles.

Left and right ventricles


This journey is far less demanding. The right ventricle only has to pump blood from the heart to the adjacent lungs.

This journey is enormous. The left ventricle has to pump blood all over the body!

Therefore, the left ventricle needs a thicker wall to generate a stronger ‘squeeze’ on the blood.

body cells

lungs

Different destinations


Drag the labels to the correct numbered boxeson the diagram of the blood system.


Traffic control


Label the heart


Answer the questions


Oxygenated or deoxygenated?


Getting things in order


Controlled circulation








Contents


Multiple choice questions



A the heart system

B the circulatory system

C the transporting system

D the pumping system

Q1

What is the alternative name for the blood system?


A heart, lungs, brain and bladder

B arteries, heart and stomach

C arteries, veins and heart

D heart, veins and pancreas

Which of the following organs are found in the blood system?

Q2


A transport substances, such as oxygen and dissolved nutrients, around the body.

B support the movement of the body.

C digest large molecules of food.

D carry chemical messages between the brain and the nerves.

The function of the circulatory system is to...

Q3


A fat tissue

B skin tissue

C nerve tissue

D muscle tissue

What is the wall of the heart mainly made from?

Q4


A The blood carries two vital materials.

B There are actually two parts to the heart.

C The system is divided into two separate circuits.

D The blood flows in two directions.

The blood system is often known as the “double circulation” system. Why is this?

Q5


A four

B it varies from human to human

C two

D none of the above

How many chambers are there in the human heart?

Q6


Name the chamber that is labelled W (becareful!).A the right ventricleB the left ventricleC the right atriumD the left ventricle

W X

ZY

Look at the diagram below.

Q7


A It would leave the heart.

B It would pass into chamber Z.

C It would pass across into chamber W.

D It would flow into all the other chambers.

W X

ZY

If blood entered the chamber X, where would it then go?

Q8


A W

B X

C Y

D Z

W X

ZY

Which chamber is the left ventricle?

Q9


A the left

B the right

C both sides are the same thickness

D middle is thicker

W X

ZY

Which side of the heart has the thickest wall?

Q10


A the right and left atrium

B the right and left ventricle

C the right atrium and the left ventricle

D the right ventricle and the left atrium

Into which chambers does blood enter the heart?

Q11


A the right and left atrium

B the right and left ventricle

C the right atrium and the left ventricle

D the right ventricle and the left atrium

Through which two chambers does blood leave the heart?

Q12


A Heart - Lungs - Body - Lungs

B Heart - Body - Heart - Body - Lungs

C Body - Lungs - Heart - Body - Heart

D Heart - Lungs - Heart - Body

Which of these combinations lists the two circuits that blood makes through the body?

Q13


P

S

Q R

U

T

Look at the diagram below.

Know what’s in your heart


A an atrium

B a ventricle

C a capillary

D a chamber

P

S

QR

U

T

What is part T?

Part 1


A a heart valve.

B the atrium.

C a chamber.

D a heart door.

P

S

QR

U

T

Part Q shows...

Part 2


A the ventricles.

B the body.

C the liver.

D the lungs.

P

S

QR

U

T

Arrow R pumps blood to the...

Part 3


P

S

QR

U

T

Arrow P shows the blood coming from the...

Part 4

A the stomach.

B the head.

C the body.

D the lungs.

© boardworks ltd 2004 1 of 53 the heart and circulatory system ks4 biology

Documents