Download An artificial heart

Cells, Human Body and Disease
Booklet 3 – Other Systems of the Body
Year 8 Science
Term 4 2012
1
The Circulatory System
The heart, arteries, veins and capillaries all
combine to form the circulatory system,
illustrated in Figure 4.3.14, which transports
oxygen, carbon dioxide, digested food,
chemicals and heat around the body and into
our cells.
The Heart
Place your right fist on the centre of your
chest and let it hang there. Your fist now
gives the approximate size and position of
your heart.
The heart pumps blood around the body,
beating at around 90–120 beats per minute
for children and 70 for adults, though superfit athletes may have heart rates below 30.
Nerve impulses generated within the heart
trigger each beat. The heart is made of a strong type of muscle called cardiac muscle and on
average pumps about 4.5 litres of blood every minute in adults, and up to 14 litres when beating
more rapidly during exercise or stress.
The human heart is really two pumps joined together that do separate jobs. One pump sends
blood to the lungs to pick up oxygen. The other receives the oxygen-carrying blood and pumps it
to the head and around the body. Blood that is rich in oxygen is said to be oxygenated, while
blood that has had most of its oxygen removed is deoxygenated. Both types of blood are red,
but oxygenated blood is a brighter red. To show the difference in diagram, blue is used for
deoxygenated blood and red for
oxygenated blood.
Notice that each half of the heart, or
each pump, has two main sections or
chambers: the atrium, where blood
enters, and the ventricle, where
blood is pumped out of the heart.
Special valves stop blood flowing or
leaking back the wrong way. The
walls of the ventricle are thicker than
those of the atrium, as they must
withstand the greater pressure
associated with blood being pumped
out at high pressure for another
circuit around the body.
2
What is Blood?
Blood carries water, oxygen and the nutrients obtained from digestion to cells around the body.
It also removes carbon dioxide and waste material from those cells and maintains our body
temperature. The average human body contains about 5.5 litres of blood made up of red and
white blood cells, platelets and plasma.
Questions:
1.
2.
3.
4.
5.
6.
7.
8.
Name the parts of the circulatory system.
State the role of the circulatory system.
Clarify the terms oxygenated and deoxygenated.
Describe the function of the heart.
Explain why the walls of the ventricles are thicker than those of the atrium.
Explain how blood serves the purpose of cells.
List the contents of blood.
Label the diagram of the structure of the heart.
3
Experiment: Dissect a heart
You will need:
 sheep's heart preferably with the blood vessels still attached
 dissecting instruments
 dissecting board
Method:
1. Identify the parts of the heart using the illustration on the previous page.
2. Try to locate where blood enters and leaves the heart:
a. to and from the lungs
b. to and from the rest of the body.
3. Sketch and label the heart and use arrows to show the direction of blood flow.
4. Cut the heart in two so that both halves show the two sides of the heart (similar to the
illustration on the previous page).
5. In a diagram, record your observations of the thickness of the walls on the left side of the
heart compared with the right side.
6. Suggest reasons for the differences observed.
7. Try to locate the valves in the heart.
Discussion
1. Describe the valves and suggest their function.
2. Write a summary paragraph about the structure and function of the heart.
Applications and uses of science: Transport technology
Heart and blood vessel diseases are the major killers in Australia. They claim twice as many
lives as cancer and 20 times more than traffic accidents. Modern medicine and technology have
produced techniques and procedures that attempt to minimise the effects of diseases and
disorders of the circulatory system.
4
Faulty heart and vein
valves
The heart, like many other
pumps, depends on a series of
valves to work properly. These
valves open and close to receive
and discharge blood to and from
the chambers of the heart. They
also stop the blood from flowing
backwards. If any of the four
heart valves becomes faulty, the
function of the heart may be
impaired.
It is now possible to replace
faulty heart valves with artificial
valves like the one shown above.
This requires surgery. The
patient may also need to take
medicine to prevent their blood
from forming clots as it flows through the artificial valve.
A faulty heart valve may be replaced by an artificial valve. Why are the heart valves so important to the
functioning of the heart?
‘If I only had a heart …’
The tin man from The Wizard of Oz would have been very happy with the development of an
artificial heart. This mechanical device can be made of titanium and plastic. Surgeons also
implant a small electronic device in the abdominal wall to monitor and control the pumping
speed of the heart. An external battery is strapped
around the waist and can supply about 4–5 hours of
power. An internal rechargeable battery is also
implanted inside the wearer's abdomen. This is so
they can be disconnected from the main battery for
about 30–40 minutes for activities such as
showering.
An artificial heart
How about that!
About 15 per cent of Australians aged between 20
and 65 have hypertension (high blood pressure).
5
This increases their chances of developing heart disease and strokes. To prevent this, people
should maintain a healthy body weight, take regular exercise and eat a diet that is low in fat and
salt.
A heart — but no pulse?
If only the left ventricle is damaged, and the rest of the heart is in good working order, a back-up
pump may be implanted alongside the heart. One model of these devices results in its wearers
having a gentle whirr rather than a pulse. This is the sound of the propeller spun by a magnetic
field to force a continuous stream of blood into the aorta.
Getting the beat!
An electrocardiogram
(ECG) shows the
electrical activity of a
person's heart. ECG
patterns are valuable in
diagnosing heart disease
or abnormalities.
To produce the ECG,
electrodes (flat pieces of
metal that are connected
to the ECG machine by
wires) are stuck to the
skin. The machine
measures the tiny
electrical impulses produced by the heart as it beats. It produces a trace similar to the one
shown in the diagram above. An abnormal trace could indicate that the patient has arrhythmia.
This is a condition where the heart beats irregularly. Another reason for an unusual trace could
be a cardiac infarction. In this condition there is dead tissue in the heart. The electrical signal
cannot travel through the dead tissue so the ECG looks abnormal. There are many other
conditions that can cause an unusual ECG, and doctors will often follow up an abnormal ECG
with further tests.
Artificial blood — a reason to support scientific research
If you lose a lot of blood, you may need a blood transfusion. The blood from another person is
injected into your veins to replace the blood you have lost. However, donated blood is always in
short supply and the blood that is transfused must match your own blood type. If the person
who donated the blood had an infection, there is also a risk of passing on that infection. What's
the solution? Artificial blood.
No-one has quite succeeded as yet in making a perfect replacement for blood but a number of
teams of scientists around the world are working on it. The ideal blood replacement would be a
6
product that has a long shelf life, does not need to be
refrigerated, does not need to match the patient's blood type
and is guaranteed to be free of disease-causing germs.
A type of artificial blood called Hemopure has been approved
to treat some cases of severe anaemia in South African
hospitals. It is made from haemoglobin obtained either from
blood that has passed its use-by date or from animal blood.
The haemoglobin is wrapped in certain chemicals so that it
behaves a lot like red blood cells do and can carry oxygen
around the body.
Hemopure is a type of artificial blood that has been approved to
treat some cases of severe anaemia in South Africa.
Hemopure is not an ideal replacement for donated blood, and it has not been approved for
human use in Australia. There are side effects to using this product. In some countries, including
South Africa, the number of people infected with HIV (human immunodeficiency virus) is much
higher than in Australia and donated blood that is free of the virus is in very short supply. In
certain instances the benefits of this blood substitute can thus outweigh the risks from the side
effects.
Activities
Remember
1.
2.
3.
4.
5.
6.
7.
Recall which group of diseases is the major killer in Australia.
Explain why valves are important to the functioning of the heart.
Outline why a patient may have surgery to insert an artificial valve.
Explain what an electrocardiogram is and when is it useful.
Describe how an ECG is used to detect heart abnormalities.
Describe how heart valves are similar to the valves in veins.
Outline the features that the ideal artificial blood would need.
Think
8. Outline some situations where hospitals would go through large amounts of donated blood in a
short time.
9. Propose why artificial blood might be particularly useful to army doctors working with soldiers
fighting wars.
10. Interpret the electrocardiograms on the previous page to answer the following questions.
a. At ‘P’, are the muscle cells of the atria contracted or relaxed?
b. After the ‘QRS’ wave, is the ventricle relaxed or contracted?
c. How does the normal electrogram differ from the abnormal electrogram?
d. Suggest what might be wrong with the heart activity shown on the abnormal electrogram
7
The Excretory System
A build-up of any waste in the body can be
harmful. Excretion is the removal of waste
from the body. Even right now, as you read
this book, you are excreting waste! You are
breathing out, removing the carbon dioxide
from your lungs and bloodstream. Along with
water, carbon dioxide is a waste product
from the respiration happening in your cells.
A waste product that is harmful if allowed to
build up is urea, produced by the liver after
protein has been digested. Protein is needed
for growth and repair, but excess protein is broken down into simpler substances, the main one
being urea. Urea passes into the bloodstream where it travels to the kidneys to be filtered out
with excess water and other waste products in the blood.
Kidneys filter an amazing 1.3 litres of blood every minute. To find your kidneys, allow your
arms to dangle straight down by your sides. Your
kidneys are located at about elbow level, towards the
back of your abdomen. Each kidney contains over a
million tiny filtration units called nephrons. About one
millilitre of blood per litre is filtered out as waste
liquid, or urine.
Urine is produced at the rate of a drop per minute, or
one to two litres per day. Urine consists of about 95
per cent water and 5 per cent urea, as well as small
amounts of salts and other substances such as bile,
which gives urine its yellow colour. Urine travels down
20 centimetre long tubes called ureters to a muscular
storage bag—the bladder, which has a maximum
capacity of about one litre. However, when the bladder
contains about 300 millilitres of urine, nerve sensors in
its walls send messages to the brain that result in the
urge to urinate—that is, allow urine to drain from the
bladder out of the body through the urethra.
Questions:
1. Define the term ‘excretion’.
2. Outline how the following wastes are produced:
a. carbon dioxide b. water c. urea.
3. Explain how waste products get to the lungs and
kidneys.
4. State how much blood kidneys can filter in an hour.
5. Identify the body part that matches each function.
8
The Respiratory System
Air is needed to supply oxygen that is
transported around the body by your
circulatory system. The cells in your body
need this oxygen for respiration.
Respiration produces carbon dioxide. A
respiratory system is needed to provide
oxygen to, and remove carbon dioxide
from, these cells.
Remember: The circulatory system
carries nutrients and oxygen to cells, and
waste products such as carbon dioxide
away from cells. Where does the blood get
the oxygen from, and where does it take
the carbon dioxide to? This is the job of the
respiratory system, which consists of the
lungs and associated structures (see figure
4.5.1).
Humans breathe between 12 and 24 times
per minute, for the most part unconsciously. This rate can vary with age, physical activity and
mood. Each breath exchanges about 500 millilitres of air. The maximum amount of air you can
breathe out (exhale) after taking a deep breath (inhale) is called the vital capacity of your
lungs. It is normally around 4500 millilitres, but may be as high as 6500 millilitres in a well
trained athlete. The composition of inhaled and exhaled air varies, because gases are exchanged
between the lungs and your bloodstream. The
movement of gases is shown in figure 4.5.5.
TASK: Determining your vital
capacity
Equipment: fully deflated balloon
Method:
1. Stretch the balloon.
2. Take a full and complete inhalation.
3. Blow into the balloon until you have
exhaled completely.
4. Tie the balloon up.
5. Measure the diameter of the balloon and
halve this figure to get the radius.
6. Use the following calculation to
determine your vital capacity in millilitres:
4
𝑣𝑜𝑙𝑢𝑚𝑒 = 𝜋𝑟 3
3
9
7. Release the air from the balloon and repeat your measurement of vital capacity three
more times. Average your results to get your best estimate of the maximum ‘blow-out’ of
your lungs.
Discussion
1. Why were you asked to stretch the balloon first?
2. Why did you measure your vital capacity four times?
3.
a. Draw up a table with the following headings.
Name
Male or
female?
Does this student play a wind Lung capacity
instrument?
(L)
b. Collect results from all the students in your class and complete the table.
c. Calculate the average lung capacity for all the girls and all the boys. Do girls have a
bigger or smaller lung capacity than boys in your class?
d. Calculate the average lung capacity for all the students in your class who play a
wind instrument. Compare that with the average value for the other students in
the class. Does playing a wind instrument have an effect on lung capacity?
4. Suggest another way of measuring the amount of air exhaled with each breath.
Parts of the respiratory system
Although air can sometimes enter the respiratory system through the mouth, most inhaled air
enters via the nose. Here it is filtered, warmed and moistened. Nostril hairs filter out larger
particles, and tiny hairlike cilia on the inside of the nose trap fine particles. The nose is lined
with mucus glands that produce sticky mucus to trap dust particles. The mucus and trapped
particles move to the back of your nose and into the pharynx. We swallow around 600
millilitres of this mucus per day without usually being aware of it. From the pharynx, air enters
the trachea (windpipe), a thin-walled tube with about the same diameter as a garden hose. At
the top, the epiglottis, a flap of tissue, stops food entering the trachea. The larynx (voice box)
also helps stop food entering.
Coughing and sneezing are both reflexes to further protect the trachea. The trachea branches
into two main bronchi, which branch successively into smaller and smaller tubes. At the end of
the smallest of these tubes (bronchioles), air enters clusters of sacs, the alveoli.
10
Gas exchange in and out of the blood takes
place here. The entire system of tubes is lined
with cilia, which beat upwards to send foreign
material back to the pharynx to be coughed out
or swallowed. Alveoli are sacs with walls only
one cell thick. There are around 500 million of
these in your lungs, with a total surface of about
80 square metres. Each alveolus lies close to the
wall of a capillary. These are also one cell thick,
so there is only a short distance for gases to
travel between the lungs and the bloodstream.
The network of capillaries in the lung is so large
that at any one time 20 per cent of the total
blood volume is in the lungs. Inside the alveoli,
oxygen moves across through the thin walls of
the tiny capillaries and into the blood. Once in
the blood, oxygen is carried by red blood cells
in a special carrier called haemoglobin.
Haemoglobin allows much more oxygen to be
carried in blood than if it was simply dissolved.
At the same time dissolved waste gas—carbon
dioxide—comes out of the capillaries back into
the alveoli, ready to be breathed out.
Replacement of the air is the result of
breathing.
Breathing is a physical process and is clearly
different from respiration, which is a chemical
reaction. Normally, you breathe without
thinking about it, but you can alter the rate and
depth of breathing with conscious effort. Take a
deep breath. Notice that your ribs move up and
out. This occurs due to the action of muscles in
the chest (the intercostals) and the
diaphragm. The diaphragm is the sheet of
muscular tissue that separates the chest from
the abdomen. The larger space in the chest
causes a pressure decrease, so air rushes into
your lungs. Now breathe out. Air is forced out
as the chest returns to its normal size.
11
Questions:
1. Identify the structure that relates to each
function.
2. Recall two structures which prevent food
from entering the trachea.
3. Describe what happens if some food finds
its way into the trachea
4. Recall the name of the special structures that give the lungs their very large internal
surface area.
5. Identify the part of the blood that contains
haemoglobin.
6. Outline the function of haemoglobin.
7. Explain why it is important that lungs have
a large internal surface area.
8. Explain how the respiratory system meets
the needs of cells.
9. Construct two pie charts to show the
composition of Inhaled and Exhaled air.
.
Experiment: Constructing a Model Lung
1. Use the equipment provided and the diagrams below to construct a model of a lung.
2. Compare your model with figure 4.5.1 on page 6 and answer the questions that follow.
Questions:
1. State which part of the
respiratory system each of the
following represents:
a. Straw
b. Balloon in the bottle
c. Rubber ‘sheet’
d. Plastic bottler
2. Explain how the lung
works. Include the words
diaphragm, trachea and lungs in
your explanation.
12
Up in smoke
About 18 000 Australians die each year as a result of diseases caused by smoking. In fact,
smoking is the largest preventable cause of death and disease in Australia.
There are clearly many long-term effects of smoking. However, the diagram below shows what
happens to you after smoking just one cigarette.
(a) Some of the health effects of smoking a cigarette, and (b) the substances in a single cigarette
There are some more obvious effects such as bad breath, body odour and watery eyes. After
several cigarettes, your teeth and fingers become stained. Your sense of taste is reduced. Even
your stomach is affected as acid levels increase.
Smoking and your lungs
Lung cancer is the most well-known disease caused by smoking. Chemicals that cause cancer are
called carcinogens. Cigarette tobacco contains a number of carcinogens. The chemicals in
cigarettes also clog up the fine hairs in your air tubes with a mixture of mucus and foreign
chemicals.
13
Coughing is the body's way of trying to clear the air tubes. However, not all of the clogging can
be cleared by coughing. The dirty mixture remains in the air tubes, causing swelling, making
them sensitive and slowing down the passage of air. Eventually the sticky mixture sinks down
into the lungs, where it blocks some of the pathways to the alveoli, where freshly breathed air
should deliver oxygen to the blood.
The diseases caused by this blocking process are called chronic obstructive pulmonary diseases,
or COPD. Emphysema is the worst of these diseases and results in the eventual destruction of
the alveoli.
Smoking and lung cancer
It seems hard to believe but there was a time when people did not know that smoking causes
lung cancer. A number of medical studies now show that there is a clear link between smoking
and the likelihood of developing lung cancer. The
two graphs on the following page show the results
of some of these studies. Can you make sense of
these graphs?
Graph 1: The risk of dying from lung
cancer increases with the number of
cigarettes smoked daily.
Activities
Graph 2: This graph shows that the number of
deaths from lung cancer has risen as cigarette
consumption has increased but there is a 20year lag time because lung cancer takes many
years to develop.
Analyse and Evaluate
1. The table on the next page shows how the popularity of smoking has changed over the past 50
years or so.
14
Percentage of adult Australians who smoke
Year
Males
(%)
1945 1964 1969 1974 1976 1980 1983 1986 1989 1992 1998 2004
72
58
45
41
40
40
37
33
30
28
29
26
Females
26
(%)
28
28
29
31
31
30
28
27
24
24
20
a. Construct a line graph of the data in the table. Use ‘Year’ on the x-axis and ‘% of adult
Australians who smoke’ on the y-axis. Draw lines for males and females in different
colours.
b. Suggest why the percentage of females who smoke has changed little while the
percentage of males who smoke has declined greatly.
c. Use dotted lines to predict the trends up to the year 2020. What percentage of males and
females do you predict will be smoking in the year 2020?
2. Study graph 1 above.
a. Copy and complete the following statements:
i.
People who smoke 10 cigarettes a day are ___________ times more likely to develop
lung cancer than non-smokers.
ii.
People who smoke 30 cigarettes a day are ___________ times more likely to develop
lung cancer than people who smoke 10 cigarettes a day.
b. If a packet of cigarettes costs $15 and contains 20 cigarettes, calculate how much a
person smoking 40 cigarettes a day spends on smoking:
i.
each day
ii.
each week
iii.
each year.
3. Study graph 2 above.
a. Describe how the incidence of lung cancer changed between 1900 and 1980.
b. Identify when the number of male smokers peaked.
c. Identify when the number of deaths from lung cancer peaked.
d. Explain why there is a 20-year gap between the two numbers.
e. The graph shows data for male smokers only. Predict when the number of cases of lung
cancer in women peaked (use the graph you drew for question 1 to answer this).
Think
4. Smoking-related diseases cost taxpayers many millions of dollars because hospitals are mostly
paid for by governments. Write down your opinion of each of the proposals below. Justify your
opinion.
a. The cost of hospital treatment for diseases caused by smoking should be paid by the
patient because it was their fault that they got sick.
b. Cigarettes should cost more. The extra money made from them could then be given to
hospitals to help pay for treating people with smoking-related diseases.
c. Cigarette companies who make profits from smoking should be made to pay for hospital
treatment of patients with diseases caused by smoking.
5. Although smoking is now banned in many places, including public transport vehicles, workplaces
and some restaurants, it is still legal. Propose why smoking has not been made illegal when it
causes so much damage?
15