the heart and circulatory system of 49 © boardworks ltd 2004 ks4 biology the heart and circulatory...

© Boardworks Ltd 20041 of 49

KS4 Biology

The Heart and Circulatory System


How the heart pumps blood


The circulatory system

Structure of the heart

Valves in the heart

Summary quiz

Contents


Which organs are involved in

this system?

How do substances move around the body?

The body has its own transport

system that carries substances

around the body.

The body’s transport system is

called the circulatory system.

Why is it given this name?

heart

blood vessels

blood


What is carried by the circulatory system?

carbondioxide

oxygen

Which gases are transported to and from the body’s cells

by the blood flowing in the circulatory system?

Oxygen is the gas needed for respiration and is transported

to the body’s cells.

Carbon dioxide is the waste gas produced by respiration

that must be carried away from the body’s cells.


The arrangement of the circulatory system means that these

two types of blood do not mix. Why is this important?

Two types of blood

The circulatory system carries two types of blood:

oxygen-rich

blood

c

oxygen-poor

blood

blood traveling

to the body cells

high oxygen content

low carbon dioxide

content

blood traveling

away from the body cells

low oxygen content

high carbon dioxide

content


How are the two types of blood (oxygen-rich and

oxygen-poor) kept apart inside the heart?

At the heart of the circulatory system

The heart is the organ at the centre of the circulatory system.

It pumps blood around the body.


Inside the heart

The inside of the heart is divided into two sections so that

the two types of blood (oxygen-rich and oxygen-poor)

are kept apart.

oxygen-poor

blood

right side

of the heart

oxygen-rich

blood

left side

of the heart

Remember that the heart is always labelled as if it is in a

body facing you, so the right side of the heart is on the

left of the diagram.


The two sides of the heart


How does blood circulate around the body?

Blood is pumped

around the body by

the heart.

It takes about 30

seconds for blood to

go once around the

body.

Starting with the left

side of the heart,

what route does the

blood follow to

complete one circuit

of the body?



The left side of

the heart pumps

oxygen-rich blood

to the rest of the body.

This blood supplies

the body’s cells with

oxygen.

What gas does the

blood then pick up

from the body’s cells

and where does the

blood go next? body’s

cells

body’s

cells


The oxygen-poor

blood needs to lose

the carbon dioxide and

pick up more oxygen.

How does it do this?


Blood picks up

carbon dioxide from

the body’s cells.

This oxygen-poor

blood then travels

back to the right side

of the heart.

body’s

cells

body’s

cells


lungslungs

Where does this

oxygen-rich blood

then travel to?


Next, the right side

of the heart pumps

oxygen-poor blood

to the lungs.

In the lungs the blood

gets rid of the waste

carbon dioxide and

collects more oxygen.

body’s

cells

body’s

cells


The oxygen-rich

blood then returns

to the left side of the

heart.

This completes the

blood’s journey

around the body.

Why is the journey

of blood through the

circulatory system

called a double

circulation?


body’s

cells

body’s

cells

lungslungs


During one complete

circuit of the body,

blood passes through

the heart twice.

The heart has two

jobs to do and so the

circulatory system

involves a double

circulation.

What are the two jobs

that the heart carries

out during this double

circulation?

A double circulatory system

body’s

cells

body’s

cells

lungslungs


Which way does blood flow?






Valves in the heart

Summary quiz

Contents


The structure of the heart – exterior

The heart pumps blood around the circulatory system.

What is the heart made of?

The heart is made of muscle and keeps pumping blood

around your body, even when you are asleep!

muscle

tissue

What do the blood vessels on the outside of the heart do?


The heart needs blood too!

The heart is full of blood but also needs its own blood

supply so that the muscle can keep pumping.

blood vessels

supply blood

to muscle tissue

The blood vessels on the outside of the heart carry

oxygen-rich blood to the heart muscle cells.

Oxygen-poor blood is then carried away from these

cells by outer blood vessels and back into the heart.

muscle

tissue


The structure of the heart – interior

The inside of the heart is divided into two sections to keep

oxygen-rich and oxygen-poor blood separate.

Each side of the heart is also divided into two sections.

Each section of the heart is called a chamber.

How many chambers are there?

right side

of the heart

left side

of the heart

4


The chambers of the heart

The four chambers of the heart have special names:

A lower chamber is called a ventricle.

An upper chamber is called an atrium (plural atria).

rightventricle

rightatrium

leftventricle

leftatrium


What do atria and ventricles do?

The chambers of the heart have different functions.

The atria collect blood that enters the heart.

The ventricles pump blood out of the heart.

blood tothe body

blood from the body

blood to the lungs

blood from the lungs


Inside the heart – labels


Inside the heart – labelling activity


Chambers of the heart – activity






Valves in the heart

Summary quiz

Contents


Preventing backflow

Blood always flows in the same direction as it moves

through the heart during each circulation of the body.

Why is it important that blood does not flow backwards?


The chambers of the heart are separated by valves

which prevent blood from flowing in the wrong direction.

Heart valves

There are valves between the atria and the ventricles…

…and there are valves leading out of the ventricles.

valve between

right atrium and

right ventricle

valve between

left atrium and

left ventricle

valve leading

out of

right ventricle

valve leading

out of

left ventricle


Naming the heart valves


How are valves held in place?

The valves between the atria and ventricles are connected

to the inner walls of the heart by tough tendons.

valve open


How are valves held in place?

The tendons allow the valves to close and hold the valve

flaps in place. They prevent the valves from flipping up

and turning inside out. Why is this important?

valve open valve closed


How do valves work?

A valve acts like a door that only opens in one direction.

If the door is held by someone at a fixed point, only the arm

moves as the door opens and closes.

When the door is closed the arm is fully extended, so the

door can only be opened in one direction.


How do valves work?

A valve acts like a door that only opens in one direction.

In the heart, the tendons holding the valve are like the

arm holding the door.

One end of each tendon is fixed to the wall of the heart

and so the valve can only open in one direction.






Valves in the heart

Summary quiz

Contents


How does the heart pump blood?

Imagine the force needed

to squeeze a tennis ball.

That’s how much force

the heart uses to pump

blood around the body!

How does the heart produce

enough force to keep doing

this 24 hours a day?

The heart can pump blood

because it is made of muscle.

Muscle tissue works by

contracting (squeezing)

and relaxing.


How does the heart pump blood?

All the parts of the heart on

either side, work together

in a repeated sequence.

The two atria contract and

relax; then the two ventricles

contract and relax.

This is how blood moves

through the heart and is

pumped to the lungs and

the body.

One complete sequence of

contraction and relaxation is

called a heartbeat.


Heartbeat animation


Stages of a heartbeat

Stage 1:

A heartbeat begins

with the heart muscle

relaxed and valves

closed.

Blood flows into the

two atria and both

sides fill up with blood.

This blood has to be

pushed through the

valves to get into the

ventricles. How does

this happen?



Stage 2:

The atria contract and

the blood is squeezed

which causes the

valves leading to the

ventricles to open.

Blood then flows from

the atria into the

ventricles.

What happens to the

open valves when the

atria are empty?



Stage 2 (continued):

The valves between

the atria and the

ventricles close.

This prevents any

backflow.

What happens next

to the blood in the

ventricles?



Stage 3:

Almost immediately,

the ventricles contract

and the blood is

squeezed again.

The pressure of the

blood forces open the

valves leading out of

the heart.

Blood is pumped out

of the heart.

What happens to the

open valves when the

ventricles are empty?



Stage 3 (continued):

When the ventricles

are empty, the valves

leading out of the

heart close and the

heart muscle relaxes.

This completes the

sequence of

contraction and

relaxation in one

heartbeat.

What will happen

next?



Stage 1 (again):

The atria fill up with

blood as the heartbeat

sequence begins

again.

Why are the walls

of the atria thinner

than the walls of

the ventricles?

Why is the wall of the

left ventricle thicker

than the right

ventricle?


What does a doctor hear when they listen to a patients’ heart?

Listening to a beating heart: lub-dub

The “lub” is caused by

the closing of the valves

leading to the ventricles.

The “dub” is caused by

the closing of the valves

leading out of the heart.

lub-dub,

The sound of a heartbeat is the sound of the heart valves.

lub-dub, lub-dub, lub-dub, lub-dub, lub-dub…


Measuring a beating heart

You can measure how

fast your heart is beating

by taking your pulse.

Each pulse that you feel

is due to the pressure of

blood leaving the heart as

the left ventricle contracts.

Place the fingertips of one

hand on the opposite wrist,

where an artery passes

near the surface of the skin.

What is your heart rate,

in beats per minute,

right now?


…in one hour?

…in one day?

…in one year?

…in 70 years?

How many heartbeats?

If your heart beats at an average rate of 70 times

per minute, how many heartbeats are there…

70 x 60 =

4,200 x 24 =

100,800 x 365 =

36, 792, 000 x 70 =

100, 800

36, 792, 000

2, 575, 440, 000

4, 200


The sequence of a heartbeat


Journey of blood around the body






Valves in the heart

Summary quiz

Contents


Multiple-choice quiz

the heart and circulatory system of 49 © boardworks ltd 2004 ks4 biology the heart and circulatory...

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