3.3.2 Mammalian heart. Applied GCE in Science Unit 3 Monitoring the activity of the human body.

3.3.2

Mammalian heart

Applied GCE in ScienceUnit 3 Monitoring the activity

of the human body

1. Blood via vena cava2. Right atrium3. Tendons on tricuspid

valve4. Right ventricle5. Left ventricle6. Left atrium7. Blood via pulmonary

vein8. Blood via aorta9. Blood via pulmonary

artery

The cardiovascular system:

1. The heart- which is the pump supplying the force to propel the blood around the body.

2. The blood vessels (arteries, veins and capillaries), in which the blood is transported.

3. The blood, which is the transport system for nutrients and other substances to and from the body organs and systems.

What is the cardiovascular system?

http://www.bbc.co.uk/learningzone/clips/the-human-heart-and-its-function/2270.html

What does our heart do?

•In mammals, the blood leaving the lung capillaries is returned to the heart before being pumped to the rest of the body. Mammals have a double circulation, the blood passing twice through the heart in each complete circuit.

•Systemic circulation - oxygenated blood is pumped from the left side of the heart to the organs of the body, and the pulmonary circulation - in which deoxygenated blood is pumped from the right side of the heart to the lungs for oxygenation.

What type of circulation do mammalian hearts have?

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.

Double circulatory system

The human circulatory system

In this first lesson 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

http://www.bbc.co.uk/learningzone/clips/anatomy-and-physiology-of-the-heart/5367.html

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. A 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.

The heart

The heart

Vena cava

Pulmonary artery

Aorta

Pulmonary vein

Name the 4 blood vessels?

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.

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

The main valves in the heart

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 squeezes 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.

valve

tendon

wall of ventricle

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

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.

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.

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.

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.

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 squeezes 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 lungs1. 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.

Plenary activity:

Activities to complete

A.. Read through lesson 1 notes you have made (covers structure of heart).

B. Use the internet or an A level Biology textbook to do the following:

• Describe the internal structure of the human heart mention all major blood vessels, valves and tendons.

•Describe in detail the cardiac cycle – labelled diagrams of atrial and ventricular systole and diastole.

• Look for a diagram and more information on the external structure of the heart and the structure of the cardiac muscle.