TEXTBOOK• thavo/tvwo • volume 2a

BIOLOGY

Colofon

Eerste druk

ISBN 978-90-5975-904-6

© Copyright 2010 OVD Educatieve Uitgeverij bv

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Auteurs: Deborah Wüst Onno Rook

Redactie: Sally Hill, Scientific Translations, Zwolle

Vormgeving: Thimo Dirkse, OVD Educatieve Uitgeverij

Illustraties: Gemma Stekelenburg, Gemm’Art, Huizen

Eindredactie: OVD Educatieve Uitgeverij

Foto omslag: Gabriella Fabbri

Foto’s: STOCK.XCHNG, Andre Verburen, Arthur Morris, Mare, Piet Spaans, Fukuri City Museum of Natural History, Sander vd Molen, freegamepick.com, verzetsmuseum.org, telegraph.co.uk, Alipo, Richard Avedon, H. Olsen, calmingsigns.nl, Everything is permutted, NOS, udel.edu, Gabriel Currie, wordpress.com, digisport.nl, ANP, freakingnews.com, jetskefotografie, d’ oale smederië, allerfre

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Content

3

Howtousethisbook 5

3 Thecirculatorysystem 9

3.1 Amatteroftheheart 103.2 Whatgoesaroundcomesaround 133.3 Highwaysandbyways 163.4 Bloodpressureandheartdisease 203.5 Thepartsofblood 233.6 Bloodclotting 263.7 Bloodgroups 273.8 Thelymphaticsystem 30

Content

4

Howtousethisbook

How

tousethisbook

5

10

Chapter 1

11

Chapter 1W1.1 What is behaviour?

BehaviourStimulusNurtureSupernormal stimulus

ResponseExternal stimulusNature

Internal stimulusMotivating factorSign stimulus

A typical scene in a classroom (fi gure 1.1): some students are holding up their hands, others are turning around to look at a student somewhere in the back of the classroom, some children are looking at the teacher.

Fig. 1.1 What has happened here?

Just like the wolves in the introductory pages these students react to changes in their environment (in this case their classroom). Behaviour is everything that an animal or human does and how it does this. The change in the environment is called a stimulus (plural stimuli). The reaction is called a response.

Let’s have a second look at the example of the classroom. The teacher asks a question (stimulus), a student gives an answer (response). This answer is wrong (stimulus), students look back, put up their hands, laugh or look at the teacher (responses). What different stimuli might the teacher respond to?

The teacher and students respond to changes outside their bodies. These are external stimuli. You can also react to stimuli inside your body, called internal stimuli. Examples of internal stimuli are hunger, thirst and pain.

The combination of internal and external stimuli determines what kind of behaviour you will show.

The science of studying behaviour is also known as ethology.

response.stimulus

behaviour

external stimuliinternal stimuli

Back to the classroom again. The teacher receives several stimuli. His response can vary, depending on his motivation. Maybe the stimulus of the held up hands will cause a response, or the students that have turned around, or those who are laughing. The teacher cannot respond to all the stimuli at once so he makes a choice. ‘The behaviour caused by stimuli is infl uenced by motivating factors.

What determines behaviour?You now know that responses to stimuli can be collectively called behaviour and that the stimuli can be external and internal. The way in which an animal or human behaves is determined by his genes (nature) and by environmental infl uences (nurture).

Nature suggests that behaviour is programmed in an animal. Nurture suggests that behaviour is only infl uenced by the environment. In reality both infl uence behaviour.

An example: The male great tit starts to sing when the days start to become longer (December/January) to let both males and females know of his presence in the area. The eggs are always laid around the middle of April, because the youngsters depend on insects and caterpillars for food. These insects and caterpillars emerge around the same time. All of these timed processes are determined by genes within the organisms. The nesting season follows the insect season (nature). Due to climate change the winters become less harsh. Insects and caterpillars emerge earlier in the year. Great tits follow with their nesting season: they adapt. Compared to 15 years ago great tits start nesting two weeks earlier (nurture). Great tits now nest at the end of March/beginning of April.

Fig. 1.2 Great tit with caterpillar

motivating factors

naturenurture

Content

GlossaryIntroduction

1.1 What is behaviour?1.2 Puzzling behaviour 1.3 Learning!1.4 Behaviour in humans

Introduction

1 Behaviour

Look at the picture in the introductory pages. What can you see? Two wolves howling at the

sky and two wolves growling to each other. Why are the wolves growling to each other? Why

are the two howling wolves ignoring them? Or are they not? What you do know is that these

wolves react to changes in their environment. They show a response which is part of their

behaviour. Behaviour is necessary for survival, not only for animals like wolves, but also for

you. You too show behaviour; even right now, while reading this text. You can say you are

displaying learning behaviour. In this chapter you will learn about behaviour.

Biology is fun. In Biology you learn about life and things to do with life. BRICKS Biology is especially written for students following bilingual education. This book is the first of two volumes. You can work with BRICKS on your own or with your classmates. Besides this textbook you will need your workbook and an answer key. Sometimes you will be directed to the internet site (www.ovdbricks.nl).

TextbookEach chapter starts with an introduction page. On this page you can read about the chapter’s topic and what you can expect. Some chapters have paragraphs on the internet site. This is clearly shown in that chapter’s content.

10

Chapter 1

11

Chapter 1W1.1 What is behaviour?

BehaviourStimulusNurtureSupernormal stimulus

ResponseExternal stimulusNature

Internal stimulusMotivating factorSign stimulus

A typical scene in a classroom (fi gure 1.1): some students are holding up their hands, others are turning around to look at a student somewhere in the back of the classroom, some children are looking at the teacher.

Fig. 1.1 What has happened here?

Just like the wolves in the introductory pages these students react to changes in their environment (in this case their classroom). Behaviour is everything that an animal or human does and how it does this. The change in the environment is called a stimulus (plural stimuli). The reaction is called a response.

Let’s have a second look at the example of the classroom. The teacher asks a question (stimulus), a student gives an answer (response). This answer is wrong (stimulus), students look back, put up their hands, laugh or look at the teacher (responses). What different stimuli might the teacher respond to?

The teacher and students respond to changes outside their bodies. These are external stimuli. You can also react to stimuli inside your body, called internal stimuli. Examples of internal stimuli are hunger, thirst and pain.

The combination of internal and external stimuli determines what kind of behaviour you will show.

The science of studying behaviour is also known as ethology.

response.stimulus

behaviour

external stimuliinternal stimuli

Back to the classroom again. The teacher receives several stimuli. His response can vary, depending on his motivation. Maybe the stimulus of the held up hands will cause a response, or the students that have turned around, or those who are laughing. The teacher cannot respond to all the stimuli at once so he makes a choice. ‘The behaviour caused by stimuli is infl uenced by motivating factors.

What determines behaviour?You now know that responses to stimuli can be collectively called behaviour and that the stimuli can be external and internal. The way in which an animal or human behaves is determined by his genes (nature) and by environmental infl uences (nurture).

Nature suggests that behaviour is programmed in an animal. Nurture suggests that behaviour is only infl uenced by the environment. In reality both infl uence behaviour.

An example: The male great tit starts to sing when the days start to become longer (December/January) to let both males and females know of his presence in the area. The eggs are always laid around the middle of April, because the youngsters depend on insects and caterpillars for food. These insects and caterpillars emerge around the same time. All of these timed processes are determined by genes within the organisms. The nesting season follows the insect season (nature). Due to climate change the winters become less harsh. Insects and caterpillars emerge earlier in the year. Great tits follow with their nesting season: they adapt. Compared to 15 years ago great tits start nesting two weeks earlier (nurture). Great tits now nest at the end of March/beginning of April.

Fig. 1.2 Great tit with caterpillar

motivating factors

naturenurture

Each paragraph starts with a keyword box. At a glance you can see what the important words are. You can also find these keywords in the margin. The text and figures provide information about the topic.

Howtousethisbook

How

tousethisbook

6

Questions

46

1 2

3 4

5

6

7 8

9

10 11

12 13 14

15 16

17

18 19

20

21

22

23

24 25

26 27

28

29

30 31

32 33

34

35

36 37

38

EclipseCrossword.com

Glossary puzzle

Sticky notes offer you fun facts about a topic.

Throughoutthebookyouwillfindseveralboxes

ExtensionboxThese boxes give you extra information about a topic that is sometimes a bit more difficult.

At the end of each paragraph you are directed to the workbook for the questions and exercises that go with the paragraph.

Completequestions1-7inyourworkbook

LanguageboxYou will find information about English in these boxes.

It will help you to understand the text better. Major

differences between Dutch and English are explained.

A lot of the exercises also practise your English. Most of the time you will not even know that you are doing so. Some exercises require you to work with a classmate. At the end of each chapter you will find a glossary puzzle. This exercise helps you to practise the keywords.

You can check your answers with the answer key.

WorkbookAnswer the questions and do the practical exercises. When you are finished with the questions belonging to a paragraph you return to your textbook.

Questions

14

16.Inthisexperimentyouaregoingtoinvestigateyourownlearningabilities.

What do you need?• Puzzleinthebackofyourworkbook.• Stopwatch

What do you have to do?1. Youwilldothisexerciseinpairs.2. Cutthepiecesofthepuzzleoutofyourworkbook.Asyoucanseeit

representsthelogoofBRICKS.Ifyoumakeamistakeincuttingyoucanobtainanewpuzzlefromwww.ovdbricks.nl.

3. Shufflethepiecesandplacethemonastackinfrontofyou.4. Makethepuzzle.5. Yourpartnerwilltimeyourresult.6. Make the samepuzzle three times in total. Each timeyouwillbe

timed.7. Switchplacesandnowtimeyourpartnerwhileheorshedoesthe

puzzle.

a. Write the times you needed to solve the puzzle in the tablebelow.

Time (in seconds)

First attempt

Second attempt

Third attempt

b. Whatcanyouconcludeafterlookingattheresultsofdoingthepuzzle?

Questions

24

11. The picture below shows a patient’s heart. This patient has an atrialseptal defect.

openingbetweenatria

AO = aorta

LA = left atrium

aortic valve

bicuspid valve

LV = left ventricleRA = right atrium

PA = pulmonary artery

pulmonary valve

tricuspid valve

RV = right ventricle

AO

LA

LV

RA

PA

RV

The atria contract. Circle the correct statement(s):1. Oxygen-poor blood will flow from RA into RV.2. Oxygen-poor blood will flow from RA into LA.3. Oxygen-poor blood will be present in RV.4. Mixed blood will flow from RA into RV.5. Oxygen-rich blood will flow from LA into RA.6. Oxygen-rich blood will flow from RA into LA.7. Mixed blood will be present in RV.

12. The picture below of another patient’s heart shows a ventricular septaldefect.

septum

a. The left ventricle pumps blood with a greater force than the rightventricle. In which direction do you think blood will flow throughthe hole in the septum?

How

tousethisbook

7

Theworkbookusesthefollowingpictograms:

you need the computer or internet to do this exercise

this is a practical exercise

you will do this exercise in a group

the glossary exercise that also summarises the chapter

pay attention, this is an important message

Websitewww.ovdbricks.nl

The website contains the sources you need to do some of the exercises. You will also find useful links and a practise test for each chapter.

So, now you know how to work with BRICKS Biology. Have fun discovering biology.

The authors of BRICKS Biology

GlossaryIntroduction

3.1 Amatteroftheheart3.2 Whatgoesaroundcomes

around3.3 Highwaysandbyways3.4 Bloodpressureandheart

disease3.5 Thepartsofblood3.6 Bloodclotting3.7 Bloodgroups3.8 Thelymphaticsystem

Introduction

3 Thecirculatorysystem

Look at this! It’s a swimmer’s paradise! There are tubes and slides in different colours,

shapes and sizes. Water flows through them at different speeds. Wouldn’t you like to take

a ride? Whirling yourself through one of the longest and fastest tubes, you probably do not

realize that you have a similar swimmer’s paradise right inside you. Small cells in your body

whirl through tubes at great speeds. These tubes are your blood vessels. Together with the

heart they make up your circulatory system. In this chapter you will learn about the circu-

latory system and the amazing stuff whirling around in it: your blood.

10

Chapter3 A3.1 Amatteroftheheart

Circulatory system VentriclePulmonary valvePacemaker

Chambers Tricuspid valve Aortic valve

AtriumBicuspid valveSeptum

Think about how many times a day you wash your hands or use the toilet. Water that comes out of the tap and water that is used for flushing the toilet are both part of the plumbing system in your house. This plumbing system consists of pipes that transport water for use and carry away waste. Your body also has a transport system for bringing nutrients and oxygen to your cells and carrying away waste, like carbon dioxide. Materials are moved through your body by the circulatorysystem. It includes a pump which is your heart, a transport substance which is your blood and many kilometres worth of tubes called blood vessels.

No circulation system can do its job properly without a pump as its driving force. Your heart is a powerful organ that actually works as not one, but two pumps! The right-hand side of your heart pumps blood towards your lungs, while the left-hand side of your heart pumps blood to all other organs of the body. This is why the left side of your heart has a thicker wall of cardiac muscle tissue than the right side.

blood to other organs

blood to other organs

blood to right lung

blood from right lung

blood to left lung

blood from leftt lung

blood from other organs

blood from other organs

aorta

left atrium

aortic valve

bicuspid valve

left ventricle

septum

right atrium

pulmonary valve

tricuspid valve

right ventricle

Fig. 3.1 Diagram of the heart and its connecting blood vessels. Note that the sides are labelled ‘left’ and ‘right’ from the owner’s viewpoint!

A baby’s heart starts beating in the fifth week of pregnancy. It can already be heard by the mother when she is three months pregnant. An average human heart beats about 42 million times per year.

circulatorysystem

11

Chapter3Your heart has four compartments called chambers. The two upper chambers are called the leftatriumand the rightatrium. The two lower chambers are called the leftventricleand the rightventricle.

Your heart beats by contracting and relaxing its cardiac muscle tissue. During one heartbeat, first both atria contract at the same time. Then when the atria relax, both ventricles contract at the same time. This repeats itself over and over throughout your lifetime.

Blood can only flow in one direction: from the atria into the ventricles and from the ventricles to the lungs and the other organs. Between each atrium and each ventricle there is a one-way valve. A valve works like a door that opens only in one direction. The valve on the right is the tricuspidvalve and the valve on the left is called the bicuspid valve. These two valves control the flow of blood into the ventricles. Between each ventricle and its connecting blood vessel there is also a valve. Both of these valves, called the pulmonaryvalve and the aorticvalve, control the flow of blood out of the heart. In figure 3.2 you can see a picture of the four valves.

aortic valve

bicuspid valve

pulmonary valve

tricuspid valve

Fig. 3.2 The valves inside the heart and in the two outgoing blood vessels

The left side of the heart contains blood that is rich in oxygen. In figures 3.1 and 3.2 this oxygen-rich blood is symbolised by a red colour. The right side of the heart has blood that is poor in oxygen. The blue colour in figures 3.1 and 3.2 symbolises this oxygen-poor blood. A wall between the left and right sides of the heart, called the septum, keeps these two portions of blood separated. If the two portions were to mix, your cells would not receive all the oxygen they need.

The heart muscle is the hardest working muscle in your body. It needs a constant supply of large amounts of oxygen and nutrients.

The bicuspid and tricuspid valves are also called the atrioventricular (AV) valves. The pulmonary valve and the aortic valve are also called the semilunar (SL) valves.

tricuspidvalvebicuspidvalve

pulmonaryvalveaorticvalve

septum

chambersleftatrium rightatriumleftventriclerightventricle

12

Chapter3

ThepacemakerThe heart’s special rhythm of contraction and relaxation is set by a group of cells that are collectively called the pacemaker. It is located in the wall of the right atrium. Nerves connect the pacemaker to the brain.

When the brain detects high levels of a waste gas called carbon dioxide in your blood, it will cause the pacemaker to speed up its rhythm. This way, the excess carbon dioxide can be quickly carried away by the blood to the lungs so that it can be breathed out.

Patients with heart rhythm problems often have an artificial pacemaker implanted (see figure 3.3) which sends electrical signals directly to the heart muscle.

right atrium pacemaker

pacemakerleads

right ventricleFig. 3.3 An artificial pacemaker

pacemaker

Completequestions1-13inyourworkbook

13

Chapter33.2 Whatgoesaroundcomesaround

Coronary circulationOxygenatedArteriesInferior vena cava

Pulmonary circulationDeoxygenatedAorta

Systemic circulationVeins Superior vena cava

The circulatory system can be divided into three sections called thecoronarycirculation, the pulmonarycirculation and the systemiccirculation. Your heartbeat controls each of these sections at the same time.

ThecoronarycirculationYour heart muscle is made up of cardiac tissue and cardiac muscle cells. These cells need oxygen and nutrients to survive and they produce waste substances that have to be removed. For this purpose your heart has its own blood vessels. The coronary circulation is the flow of blood to and from the cardiac tissues.

coronary arteries

coronary veins

aorta

Fig. 3.4 The coronary blood vessels

ThepulmonarycirculationThe flow of blood from the heart to the lungs and back to the heart is called the pulmonary circulation. It connects the heart with the lungs by means of blood vessels which are called veins and arteries. Veins carry blood towards the heart while arteries carry blood away from the heart. You will learn more about veins and arteries in section 3.3.

All the cells in your body need oxygen to survive. Your blood picks up this oxygen in your lungs. Here, the blood becomes oxygenated, or oxygenrich. Your blood then transports the oxygen it has picked up along your two pulmonaryveins (one from each lung) towards the heart, where it enters the left atrium (see figure 3.5). Your blood is now ready to transport the oxygen to your cells.

coronarycirculationpulmonarycirculationsystemiccirculation

veins arteries

oxygenated

pulmonaryveins

14

Chapter3

When the oxygen is delivered to the cells of your body, your blood becomes oxygen-poor or deoxygenated. This blood also contains a lot of waste such as carbon dioxide gas made by your cells. When your heart receives this blood, the right ventricle pumps it away to your lungs along your two pulmonaryarteries. Now you can breathe the carbon dioxide out.

At the same time, your blood picks up a new portion of oxygen when you breathe in. Then this new portion of oxygenated blood enters the left atrium again for another round of circulation through your body.

blood to other organs

blood to other organs

blood from other organs

blood from other organs

left atrium

left ventricle

right atrium

right lung

left lung

pulmonary vein

pulmonary artery

capillaries

right ventricle

Fig. 3.5 The pulmonary circulation

ThesystemiccirculationOxygenated blood is transported to all of your other cells, tissues and organs by means of the systemic circulation. This section of the circulatory system also transports waste substances from the cells back to your heart.

Oxygenated blood is pumped away from the heart to the cells through arteries. The main artery that transports blood directly away from the heart is called the aorta. The aorta splits up into smaller arteries such as the liver artery, the intestinal arteries and the renal (kidney) arteries.

Deoxygenated blood is transported from the cells towards the heart through veins. The two main veins that transport blood directly from the organs back into the heart are called the superiorvenacava and the inferiorvenacava. Both of these veins collect blood from smaller veins such as the liver vein and the renal veins. In figure 3.6 you can see a diagram of the main arteries and veins of the systemic circulation.

When blood leaves your heart, it travels about 1 metre per second (3.6 kilometres per hour) when you are at rest. It slows down as it gets into the smaller arteries. A drop of blood travels from your heart down to your toes and back again in about one minute.

deoxygenated

pulmonaryarteries

aorta

superiorvenacavainferiorvenacava

15

Chapter3

Superior in Latin means ‘upper’ and inferior means ‘lower’.

Fig. 3.6 The systemic circulation

Completequestions14-23inyourworkbook

internal jugular vein carotid artery

heart

aorta

aorta

superior vena cava

inferior vena cava

16

Chapter3 h3.3 Highwaysandbyways

Capillaries

When you travel in a car between two cities on a highway, you probably encounter cars and motor cyclists travelling in opposite directions. After a while you will exchange the highway for a smaller byway, where traffic leaving the city will again pass you in the opposite lane. In contrast, your blood travels only in one direction and nothing passes in the opposite direction. It travels on a one-way street.

The one way streets in your body are your arteries and veins. The cars and motor cyclists are the substances such as oxygen and carbon dioxide travelling along your blood. Blood moves by the pumping action of the heart, from arteries into veins.

But how exactly does blood travel out of an artery and into a vein? In the middle of the 17th century, scientists began to use microscopes and they discovered capillaries, the tiny blood vessels that connect arteries with veins. They found out that blood is pumped away from the heart into arteries, then into capillaries, then into veins and finally it arrives back into the heart.

smooth lining

smooth muscle

valve

artery vein capillary

smooth muscle

connective tissue connective tissue

elastic connective tissue elastic connective tissue

Fig. 3.7 The three types of blood vessels

ArteriesThe two ventricles of the heart are each connected to a major artery. The left ventricle is connected to your aorta and the right ventricle connects with your pulmonary artery. These two arteries branch out towards your organs and tissues. Blood in the arteries can only flow away from the heart because of the force of the heartbeat. Arteries must be capable of handling the high pressure with which the heart pumps the blood away. This is why arteries have thick, elastic walls made of connective tissue and smooth muscle tissue (see figure 3.7).

There are over 161,000 kilometres of blood vessels in an adult’s body. If these blood vessels were lined up end to end, they would circle the equator four times!

capillaries

17

Chapter3VeinsWhen blood enters veins it does not have the same high pressure that exists in the arteries. This is why veins are less muscular but wider (see figure 3.7). In order to make sure the blood keeps flowing towards the heart and does not fall back under low pressure, the veins are equipped with one-way valves (see figure 3.8). These are similar to the ones inside the heart. The valves close when blood tries to flow backwards.

Fig. 3.9 Photo of a valve inside a vein. This valve is open. Source: Advanced Mobile Diagnostics, Inc.

The flow of blood in your veins is also helped by your skeletal muscles. When your skeletal muscles contract, the veins inside them are squeezed and blood moves towards the heart (see figure 3.10).

upper valve

muscle

vein

ab

clower valve

muscle relaxed,valves closed

muscle contracts, uppervalve opens and bloodis forced upwards, lowervalve remains closed

muscle relaxes, uppervalve closes, lower valveopens as a result of musclecontraction elsewhere andblood flows forwards

blood flow towards the heart

Fig. 3.10 The action of muscles on a vein

open

closed

Fig. 3.8 The action of a valve inside a vein

veinwall

veinwall

valve

18

Chapter3

ThediscoveryofbloodcirculationThe fact that veins have valves was discovered by William Harvey, an English physician who studied blood circulation. In 1628 he published his discoveries in a book he called Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, which means ‘On the Motion of the Heart and Blood in Animals’. In figure 3.11 you can see a drawing of one of his experiments.

Fig. 3.11 Drawings from William Harvey’s experiments.Source: Wellcome Institute Library, London

Harvey bound the upper arm of a volunteer. This way blood in the veins of the forearm could not flow back to the heart. This made the veins in the forearm swell up and become clearly visible. In ‘Figura 1’ you can see swollen veins in the forearm and the position of the valves. ‘Figura 2’ shows that if you push blood away from a part of the vein and press onto the vein, it does not fill until the finger is released. ‘Figura 3’ shows that blood cannot be forced in the ‘wrong’ direction.

The left atrium is connected to your pulmonary veins. Your right atrium connects with the superior vena cava, which returns blood from your head, and with the inferior vena cava, which returns blood from your abdomen and lower body.

19

Chapter3CapillariesArteries and veins are connected to each other by tiny blood vessels called capillaries. The pressure inside capillaries is very low. The walls of capillaries are just one cell layer thick. Capillaries are very narrow, about 0.001 mm in diameter. When you look at the corners of your eyes, you can see the capillaries as tiny red lines on the sclera. Because the walls of capillaries are so thin, oxygen, water and nutrients easily flow out of them and into the tissues and cells that surround them (see figure 3.12).

tissue cells

plasma

O2

CO2

systemiccapillary

red bloodcell

Fig. 3.12 A capillary in a tissue.

In the same way, carbon dioxide and waste easily flow out of the cells and into the capillaries to be removed.

Some nutrients in the blood capillaries are pushed through the thin walls by the force of blood pressure. In the next section you will read more about this.

Completequestions24-29inyourworkbook

There are about 40 billion capillaries in your body. They make up the majority of the body’s circulatory system.

20

Chapter3 B3.4 Bloodpressureandheartdisease

Blood pressureHypertensionStroke

SystoleAtherosclerosisHeart attack

DiastolePlaqueCardiac arrest

It’s your brother’s birthday! You help decorate the living room by blowing up some balloons. The force of the air inside the balloon pushes on its wall. You can actually feel the air pressure when you hold the balloon in both of your hands as you blow more air into it.

Fig. 3.13 The air pressure inside a balloon

Your circulatory system is similar to the balloon. Instead of blowing air into it, your heart pumps (and circulates) blood into the arteries every time it beats. The pressure of your heartbeat moves through your blood. Your bloodpressureis the force of the blood on the walls of your blood vessels. This blood pressure is highest in the arteries and lowest in the veins. When you place your fingers gently on the sides of your neck or on an artery on the inside of your wrist (see figure 3.14), you can feel the waves of blood pressure. These waves have the same rhythm as the beat of your heart.

Fig. 3.14 Taking your pulse

bloodpressure

21

Chapter3

Takingyourpulse?

When you feel the blood pressure on the inside of your

wrist, this is called ‘taking your pulse’ in English. A ‘pulse’

is actually defined as a ‘beat’. Dutch pupils often confuse

the word ‘pulse’ with the Dutch word ‘pols’ which means

‘wrist’ in English. It is a funny coincidence that when

you take your pulse, you usually do this at your ‘pols’!

Actually, you can take your pulse at any artery that lies

close to the surface.

Fig. 3.15 Measuring blood pressure

Doctors or nurses usually measure your blood pressure at a large artery in your arm (called the brachial artery, see figure 3.15). Their measurements are expressed by two numbers, such as 120 over 80. The first number is called the systole which is the pressure when the ventricles contract and blood is pushed away from the heart. The second number is the diastole, which is the lowered pressure caused when the ventricles relax and fill up with a new portion of blood.

HypertensionBlood pressure does not stay the same all the time: it changes to meet your body’s needs. At times when you are very active or when you are angry, scared or stressed your blood pressure goes up. When you are calm or at rest your blood pressure goes down again to normal levels. If blood pressure remains high this is called hypertension. The heart must work harder to keep the blood flowing and this places an extra strain on it. It is a condition that can lead to serious problems such as a heart attack, heart failure, kidney disease or a stroke. A stroke occurs when one of the arteries that transport blood to the brain is blocked or ruptured.

AtherosclerosisOne cause of hypertension is atherosclerosis. In this condition, fatty materials are deposited on the inside walls of the arteries. This fat comes from foods such as fried snacks or greasy crisps. The build-up of fat can occur in any artery in the body, but deposits in the coronary arteries are especially dangerous. A clogged artery can increase the blood pressure inside

cuffgauge

brachial artery

pump

systolediastole

hypertension

stroke

atherosclerosis

22

Chapter3

it. When fat completely blocks the artery, blood flow inside it stops. When the coronary circulation is blocked, part of your cardiac tissue can stop functioning properly. This can result in a heartattack.

normal artery

blood flow plaque

artery narrowed byatherosclerosis

Fig. 3.16 The formation of a plaque causes abnormal blood flow

The fatty deposits inside an artery can become stiff and hard and form a plaque (see figure 3.16). If this happens, the artery loses its elasticity and is no longer able to expand with the rhythm of the heartbeat. It can burst. This is what causes a stroke.

heartattack

AnAEDinyourschoolWhen a person’s heart stops, this is called a cardiac arrest. His or her life may be saved if an AED is close by. AED stands for Automatic External Defibrillator. It is a small handheld device which gives an automated electrical shock in order to get the heart beating again.

Today many Dutch government buildings, offices and schools are equipped with an AED.

Fig. 3.18 The AED logo Fig. 3.17 An AED on the wall

Does your school already have one?

Risk factors that increase the chance of getting heart disease are: eating fatty foods, smoking, not doing regular sport or exercise and being overweight. Also, the chances of getting heart disease increase with age. Living a healthy lifestyle decreases the chance!

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Chapter3T3.5 Thepartsofblood

PlasmaPlateletsLymphocytes

Red blood cellsHaemoglobinAntibodies

White blood cellsPhagocytesImmune

In the previous sections you have read about the circulatory system. But why do we have a circulatory system? You have already learned that blood transports all kinds of substances:

• Oxygen is carried from your lungs to your cells.• Carbon dioxide is carried from your cells to your lungs to be breathed

out.• Nutrients are carried from your intestines to your cells.• Waste is carried from your cells to your kidneys to be removed.

Blood also transports heat to keep your body temperature at a constant 37o Celsius. If on a winter’s day your fingers are cold from throwing snowballs, your blood flow warms them up again when you are done. This way your fingers will not freeze. If you get warm from running around on a soccer field, blood transports heat away from your muscles towards areas such as your skin and you will sweat and cool down before you overheat.

Is there anything else flowing around in this blood of yours? Let’s find out in this section!

Sometimes a doctor might ask you for a blood sample. When some of your blood is drawn into a test tube, it feels warm and it looks red all over. But when the sample is left on the desk for a little while, the blood naturally separates into two large parts with a small part in between (see figures 3.19 and 3.20).

PlasmaThe yellow liquid part of blood is mostly water and it is called plasma. It makes up about 55% of your blood. Nutrients, waste substances like carbon dioxide, hormones and some of the oxygen are dissolved in plasma.

Fig. 3.19 A blood sample left standing, on the left

plasma

A cubic millimetre of blood contains about 5 million red blood cells, which have a lifespan of about 120 days. They are made at a rate of 2 to 3 million per second! Red blood cells wear out and are destroyed in the liver at about the same rate.

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Chapter3

BloodcellsThe two layers below plasma contain the blood cells. They make up about 45% of your blood. Because they are heavier than water, they have settled in the lower half of the test tube. There are two main types of blood cells:redbloodcells and whitebloodcells. Furthermore there are platelets, which are not really cells but tiny fragments of cells. The white blood cells and the platelets form a thin layer on top of the red blood cells.

55% plasma

45% red blood cells

plateletswhite

blood cells

Fig. 3.20 The parts of blood

Blood cells and platelets are made inside the bone marrow of long bones like the femur. You can see a picture of platelets and both types of blood cells in figure 3.21.

platelet

blood vessel

white blood cell

red blood cell

A cubic millimetre of blood can contain as many as 400,000 platelets.

redbloodcellswhitebloodcells

platelets

haemoglobin

Fig. 3.22 A microscopic photo showing many red blood cells (1), platelets (2) and white blood cells (3)

Red blood cells are disc-shaped. They are different from all your other body cells because they have no nuclei. They contain a red substance called haemoglobin. Haemoglobin binds most of the oxygen, which is why your blood can transport it. Since there are a lot more red blood cells than white blood cells, your blood has a red colour.

1

2

3

Fig. 3.21 Red blood cells, white blood cells and platelets in a blood vessel

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Chapter3White blood cells do have nuclei. They fight bacteria, viruses and other invaders of your body which may cause disease. Your body reacts to invaders by increasing the numbers of white blood cells. White blood cells can change their shape and squeeze themselves through capillary walls. This allows them to enter the tissues that have been invaded.

There are many types of white blood cells. Each protects you against disease in a different way. Phagocytes can stretch themselves to engulf and ‘swallow up’ bacteria. Then they cut the bacteria into small pieces that are no longer harmful. Lymphocytes make substances called antibodies, which are specially produced to help destroy one type of invader each time. If the same invader gets inside the body again, the lymphocytes will know how to make the same antibodies even faster. This means your body is immune to the invader: you will not get ill!

Platelets help to clot blood. You will learn more about blood clotting in the next section.

Completequestions37-43inyourworkbookA cubic millimetre of blood has about 5,000 to 10,000 white blood cells.

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Chapter3 B3.6 Bloodclotting

FibrinogenScab

FibrinHaemophilia

Clot

Ouch!! You accidentally scratched yourself on a piece of sharp wood that was sticking out! A splinter has got itself into your skin. Quickly you pull the splinter out. Fortunately, the wound is not very deep. Right away some blood starts oozing out of your wound. After a while however, the bleeding stops and your body forms a tiny crust on top of the wound. Your skin is being healed. How does your body perform this miraculous feat?

Bleeding stops because your platelets do something amazing. They change a substance in your plasma called fibrinogen into sticky thread-like fibers called fibrin. Fibrin forms a net which traps escaping blood cells and plasma. By doing this it forms a clot. The clot helps stop more blood from flowing out. It also stops bacteria from getting inside. Below the hardened clot, which is called a scab, your skin cells are being repaired. As more new skin cells grow, the clot is pushed upwards and eventually falls off. Your skin has healed!

platelets

fibrinwood splinter

platelets

white blood cells

red blood cells

Fig. 3.23 A wound is protected by the formation of a clot

You can also get a wound underneath your skin, for instance when you bump into something. If this happens, a clot forms in a similar way to prevent your broken blood vessels from leaking blood. You can clearly see the scab which forms a blue mark below your skin.

Some people have an inherited disease called haemophilia. Their blood cannot clot properly. A small injury can be a big problem for someone with haemophilia. When bleeding does not stop, it can even be deadly. Today, there are medicines to treat patients with haemophilia.

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Chapter3b3.7 Bloodgroups

Blood transfusion Blood group Antigens

When a wound is small, blood clotting quickly stops blood leaking away. However, if you have a large wound you may loose a dangerous amount of blood. When this happens, you need a bloodtransfusion. You receive blood cells or plasma from a plastic bag through a vein in your arm. But there is a catch! You cannot receive blood from just anybody. You must get the right bloodgroup. If the wrong kind is given, your blood cells may clump together and form clots inside your blood vessels. This can be fatal if the blood vessels become blocked.

Fig. 3.24 A blood transfusion being prepared

So, what are blood groups and how can you find out which group you have? You will read about it in this section.

TheAB0systemThere are four main blood groups, called A, B, AB and 0 (called zero, sometimes also called “O”). The groups are different because of the presence or absence of two kinds of chemical tags on the red blood cells called antigens. The antigens can be either A or B (see figure 3.24).

• Group A red blood cells have A antigens.• Group B red blood cells have B antigens.• Group AB red blood cells have both A and B antigens.• Group 0 red blood cells have no antigens (which is why they are

called “0”).

Each blood group also has specific antibodies in their plasma. As you may remember from section 3.5 antibodies can help destroy invaders. They can also help destroy red blood cells from the wrong blood groups! There are two kinds of blood antibodies: anti-a and anti-b (see figure 3.24). One kind of antibody can match one kind of antigen and attack it.

bloodtransfusion

bloodgroup

antigens

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Chapter3

red blood cell

antigen A

anti-B antibodies

anti-A antibodies

neither anti-A nor anti-Bantibodies

both anti-A and anti-Bantibodies

antigen B antigen A and B neither antigen A nor B

plasma

Fig. 3.25 The antigens and antibodies of the A B 0 System

• Group A plasma has anti-b antibodies which will attack B antigens. • Group B plasma has anti-a antibodies which will attack A antigens.• Group AB plasma has no antibodies.• Group 0 has both anti-a and anti-b antibodies and will attack both

A and B antigens.

This means the choices of blood transfusions you can receive are limited by which kind(s) of antibodies you have, see table 3.1.

Blood Group Can receive Can donate to

A Aand0 AandAB

B Band0 BandAB

AB all AB

0 0 allTable 3.1 Blood transfusion choices

BloodtypingHow can you find out which blood group you have? In order to do this, you will need a solution of anti-a and a solution of anti-b antibodies. Two drops of blood are placed on a glass slide. Some anti-a antibodies are added to the first drop. To the second drop some anti-b antibodies are added. If a drop of blood shows clotting, the antibodies have attacked matching antigens present on the blood cells. If a drop of blood does not clot, the antibodies have not found matching antigens to attack (see figure 3.26).

A B AB 0

Fig. 3.26 The result of four blood typing tests

with anti a

with anti b

The first blood transfusions took place in the 1600s and were from animal to animal, and then from animal to human.

In 1818, James Blundell, a British doctor, performed the first successful transfusion of human blood to a patient. The patient was lucky. Dr. Blundell did not yet know about blood groups!

In 1901, dr. Karl Landsteiner discovered them. This earned him the 1930 Nobel Prize.

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TheRhesusfactorThere is another separate kind of antigen called the Rhesus factor. If the Rhesus antigen is found on red blood cells, this is called Rhesus positive (Rh+). If no Rhesus antigen is present this is called Rhesus negative (Rh-). Each of the four blood groups can be either Rh+ or Rh- which makes: A+, A-, B+, B-, AB+, AB-, 0+ and 0-.

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Chapter3

Lymph in Latin means “clear water’.

T3.8 Thelymphaticsystem

Lymph vesselsTissue fluid

Lymph capillariesLymph nodes

Lymph

You are thirsty and turn on the faucet to fill a glass of water. You get distracted and do not watch what you are doing. The glass is already full and water starts to overflow your glass! Fortunately the excess water flows down the drain of the sink. Your body’s excess fluids are removed from your tissues in a similar way by the lymphatic system.

The lymphatic system consists of lymph vessels and lymph capillaries that transport a clear liquid called lymph. Similar to veins in the blood circulatory system, lymph vessels in the lymphatic system have valves. Lymph is transported by means of these valves and with the help of skeletal muscles. Unlike the blood circulatory system, the lymphatic system has no pump. Lymph does not circulate either.

Fig. 3.26 The lymphatic system

So what is the connection between the blood circulatory system and the lymphatic system? The answer is: tissues and cells!

As oxygen, nutrients and water move through the walls of blood capillaries (see section 3.3) they become part of the tissuefluid. This is a fluid that fills the spaces between cells that make up a tissue.

Most of this tissue fluid is absorbed by the cells. Some of it flows right back into the bloodstream. A small amount of tissue fluid is left behind. If this would continue even for a brief period of time, the tissue fluid would build up dangerously. Tissues could be destroyed and this could be fatal. The excess tissue fluid needs to be drained.

lymphvesselslymphcapillaries

lymph

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Chapter3This excess fluid is collected by the lymphatic system. After tissue fluid flows into lymph capillaries, it is called lymph. It is transported and drained back into your blood at veins close to your heart.

lymph capilary

small artery

lymph

tissue cells

tissue spacesfilled with

tissue fluid

small vein

lymph vessel

Fig. 3.27 Lymph capillaries (green) in a tissue

Before going back into the blood stream, lymph needs to pass lymphnodes which are bean-shaped organs found throughout your body. In here, lymph is filtered from bits and pieces of bacteria and other invaders that the lymphocytes picked up and destroyed. When you have an infection, your lymph nodes fill up with lymphocytes and become swollen and sometimes painful. You can especially feel this at the sides of your neck, where many lymph nodes are found!

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Aabdominalbreathing 33alveoli 26alveoli 29antibodies 55antigens 57aorta 44aorticvalve 41arteries 43asthma 35atherosclerosis 51Bbehaviour 10behaviouralsequence 14behaviouralunits 14bicuspidvalve 41bloodgroup 57bloodpressure 50bloodtransfusion 57breathing 33bronchi 26bronchi 29bronchioles 26bronchioles 29bronchitis 35Ccapillaries 46cardiacarrest 52chambers 41chestbreathing 33circulatorysystem 40classicalconditioning 19conflictingbehaviour 17COPD 35coronarycirculation 43criticalperiod 18culture 22Ddeoxygenated 44diaphragm 33diaphragmaticbreathing 33diastole 51diffusion 31Eemphysema 35epiglottis 27externalstimuli 10Ffibrin 56fibrinogen 56

Ggasexchange 30Hhaemoglobin 54haemophilia 56hayfever 36heartattack 52hypertension 51Iimitation 18immune 55imprinting 18inferiorvenacava 44intercostals 33internalstimuli 10Llarynx 26leftatrium 41leftventricle 41lungcapillaries 30lungs 26lungvolume 34lymph 60lymphcapillaries 60lymphnodes 61lymphocytes 55lymphvessels 60Mmotivatingfactors 11Nnasalcavity 26nature 11norms 22nurture 11Oolfactorycells 27operantconditioning 20oralcavity 26oxygenated 43Ppacemaker 42phagocytes 55pharynx 26pharynx 27plaque 52plasma 53platelets 54pulmonaryarteries 44pulmonarycirculation 43pulmonaryvalve 41pulmonaryveins 43R

Index

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redbloodcells 54residualvolume 34respiration 31response 10rightatrium 41rightventricle 41Sscab 56septum 41signstimulus 12stimulus 10stroke 51superiorvenacava 44supernormalstimulus 12systemiccirculation 43systole 51Tthoracicbreathing 33tidalvolume 34tissuefluid 60trachea 26

trialanderror 20tricuspidvalve 41Uuvula 27Vvalues 22veins 43vitalcapacity 34vocalcords 27voicebox 27Wwhitebloodcells 54windpipe 26

Index