CHAPTER 12
HEALTH AND DISEASE
19
12.1 DEFENDING YOUR BODY AGAINST PATHOGENS
According to many teachings, disease is part of our lives. Buddha claimed that birth, disease, ageing
and death are natural parts of existence that is bound to the body. However, the better your
homeostatic and defence mechanisms, the lower your chances of developing a disease.
The body of living organisms is in a state of constant change. Some of these changes are
necessary and are in harmony with the organism, because the organism knows how to handle them.
Other changes are new, unexpected, quick or harmful. Many times, these changes last for a
short time only, and then the body can restore its own balance. This is so because homeostasis
balances out the changes. However, if these changes exceed a certain range of tolerance for a
remarkable period of time, the organism will be at ‘lack of ease’, and so it will develop a ‘disease’. In
many cases still, the balance of the body can be restored, but it often requires assistance, such as
medical treatment or medicine. Yet, in some of the cases, the balance cannot be restored, and the
disease results in death. There are several ways one can get ill.
Questions and exercises
1.
One can actually catch a disease. These are called infectious diseases. The way infectious diseases
can spread are listed below. Match the ways with these diseases or pathogens: Cholera, Salmonella,
cold or flu, malaria via Anopheles mosquito, athlete’s foot or headlice, hepatitis B or HIV. (based on
Pickering: Biology, p. 278)






2.
by drinking contaminated water (e.g. _____________)
by eating contaminated food (e.g. _____________)
by direct contact (e.g. _____________)
by animal vectors (e.g. _____________)
by droplets in the air (e.g. _____________)
via body fluids (e.g. _____________)
Non-infectious diseases can be of several types. One categorisation can be seen blow. Match the
name of each category to a paragraph below: degenerative disease, deficiency, allergy,
inherited/metabolic disease, mental/psychological condition, environmental-induced disease, selfinduced disease. (based on Pickering: Biology, p. 279)
a.
b.
c.
d.
e.
f.
g.
Some failure in the body’s normal set of chemical reactions, e.g. sickle cell anaemia (abnormal
haemoglobin); or diabetes (failure to produce enough insulin). These conditions are due to
alterations in the genes. ____________________
Sensitivity to some antigen in the environment, e.g. hay fever (pollen is the antigen).
____________________
Organs and tissues work less well as they age. This is thought to be due to changes in body
chemicals caused by free radicals such as the peroxide ion [, or deposits of various materials]. E.g.
coronary heart disease, cataracts, hardening of arteries. ____________________
Some factor may trigger a dangerous or abnormal reaction, e.g. overexposure to ultraviolet
radiation may cause abnormal cell division leading to skin cancer. ____________________
Changes in the working of the brain may lead to problematic behaviour, e.g. schizophrenia,
depression. ____________________
Poor diet may deprive the body of some essential substance e.g. scurvy is caused by lack of
vitamin C. ____________________
Some abuse of the body may affect its function, e.g. lung cancer caused by cigarette smoking;
cirrhosis of the liver caused by alcohol abuse. ____________________
Buddhist medicine puts diseases into four categories. Those caused by: 1) a lack of awareness (e.g.
accidents); 2) an improper diet; 3) suppressed emotions; 4) karma (the result of actions carried out by
the individual in the past). Vedic medicine and traditional Hungarian folk medicine claim that diseases
20
originate from one or more of these basic causes: 1) desire, 2) anger, and 3) attachment, but the
primary cause of each is the improper knowledge of the Self.
12.1.1 THE FIRST LINE OF DEFENCE
Our environment is full of microorganisms. Most of these are neutral or even benevolent, but some are
parasites, which do harm to our bodies once they manage to get inside. Pathogens can do harm by
using our body as a food resource and breeding ground. It is very important that our tissues should be
as protected from these parasites as possible. However, we should not forget that harmony in mind and
body is the best defence!
One way of defending the body against intruders occurs by maintaining an intact surface: strong
and resistant mucous membranes and skin. However, if we cut ourselves, or bite the inside of our
mouth, the integrity of our surfaces will be lost. Through the cuts, bruises or wounds, pathogens may
enter the body, so the surface has to be closed and healed as quickly as possible. This is exactly what
blood clotting does.
Besides blood clotting, there are several other mechanisms that defend the integrity of our body
surfaces: 1) the microbes in our mouth are swallowed, and most of them are destroyed by gastric juice
in the stomach; 2) the tear contains lysozyme, an enzyme that breaks down bacterial cell walls; 3) the
ears are protected by earwax; 4) the goblet cells in the trachea trap microorganisms, and the cilia help
wafting them upwards – finally coughing removes them from the body.
12.1.1.1 Blood clotting
1.
Read the following text, and fill in the gaps.
Blood clotting helps prevent intrusion by _____________, as well as stopping us from losing too
much _____________. The most important elements that take part in blood clotting are
_____________ and several proteins.
When a blood vessel is cut, the
platelets bump into the edges of the
cut, and release a chemical (surface
contact). The damaged _____________
also release chemicals (tissue factors).
Produced by the liver, there are several
important blood clotting factors (proteins)
that get activated by these chemicals,
to start a cascade reaction chain.
Fig. 12.1 shows the most
important steps in this. The chain of
reactions ends in one protein, called
prothrombin being converted into
_____________, an enzyme that
activates
a
reaction
turning Fig. 12.1 Major steps of the blood clotting cascade
_____________
into
_____________. While most blood clotting factors are soluble, fibrin is _____________ in
blood. Fibrin forms a net of fibres all across the cut. This net traps red blood cells and platelets,
21
and, together with these, soon forms a blood
_____________ that stops further bleeding. As you can see,
Ca2+, vitamin K and some _____________ are important
blood clotting factors as well.
Bleeding may occur inside the body, or on a body
surface. If the clot forms on the skin, the clot is called a scab.
(See Fig 12.2) Beneath the scab the tissue can become
inflamed, which is red and painful. This time, mast cells (a
type of connective tissue cell) produce a substance called
histamine, which dilates blood vessels, and allows
_____________ to leak out of them. The extra plasma helps
dilute toxins that may have entered the wound.
In an accident, severe blood loss (called haemorrhage) can
cause many problems. It may lead to very low blood
pressure, and the tissues of vital organs remain without
oxygen and food. The body enters a state of shock. If the
victim has no pulse, or is not breathing, measures are taken
to restart these functions. Also, a strongly bleeding wound
needs to be tended to.
2.
Answer these questions below:
a.
b.
c.
3.
What is the body’s first line of defence?
Why is blood clotting important in defending the body?
What is a shock?
Fig 12.2 Blood clotting (from
www.harunyahya.com/signs_design_07.php)
The text (modified from www.SpringfieldFAS.org) below is about first aid methods of treating cuts,
scrapes and bleeds. Fill in the gaps using these words: gauze, mouth, elevated, dried, headache,
forefinger, pressure, lower, remove.
Nosebleed
Sit upright or lean slightly forward. Use your thumb and _________________ to pinch your nose. Do
not release the pressure for at least 10 minutes. Breathe through your _________________ during this
time. Call an ambulance if the bleeding continues or you feel lightheaded, dizzy or have a severe
_________________.
Minor Cuts and Scrapes
Stop the bleeding by pressing a _________________ pad or clean cloth against the wound. Once
bleeding stops, clean the area with mild soap and water, dry gently with a clean cloth (do not remove the
_________________ blood) and cover with a protective bandage. If the bleeding does not stop after
several minutes of applying _________________, call an ambulance.
Severe Bleeding
Call an ambulance immediately. Lay the patient down. If possible, the head should be slightly
_________________ than the rest of the body and the area that is bleeding should be
_________________ above the heart. Apply steady, firm, direct pressure to the wound with sterile gauze
or a clean cloth. If the first piece of gauze or cloth is soaked through, add another on top of the first but
do not _________________ the previous layer. Once bleeding stops, keep the patient still until help
arrives.
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12.1.2 THE SECOND LINE OF DEFENCE: THE IMMUNE SYSTEM
Another, more complex way of defending the body against microscopic pathogens is carried out by the
immune system. The cells taking part in the process are called white blood cells. White blood cells
have got two main types: phagocytes that engulf foreign bodies, and lymphocytes that launch specific
attacks against the intruders.
In a viral disease, millions of viruses may enter the body through ‘gates of infection’ such as the
mucous membrane of the throat, guts, urogenital passages, or through cuts in the skin. As you may
remember, viruses are particles made up of protein and nucleic acid. In other cases, when bacteria or
fungi infect the body, the ‘enemies’ are cellular, but they use very similar ‘gates’ to enter. No matter
what their form or type, after the pathogens have penetrated the tissues, they can be immediately
recognised by patrolling phagocytes.
Phagocytes move around like amoebae in the soft tissues, and have a delicate system of
identification by which they can distinguish which cells are ours and which are not. Each cell or
particle has its own ‘identity card’ on its outside, usually a small molecule of protein or carbohydrate
called the antigen. The phagocytes ‘scan’ exactly these ‘identity molecules’, and attempt to engulf
those cells or particles whose antigen they recognise as ‘foreign’. In fact, phagocytes have many types
of receptor molecules in their cell membrane that can recognize a wide range of possible antigens. In a
virus, the antigens are the proteins of the virus coat. In cellular pathogens, these are molecules of the
cell wall or cell membrane. After identifying the antigen, the phagocyte engulfs the whole
microorganism. Antigen recognition is easier for phagocytes if an antibody molecule is already
attached to the antigen (see later).
Phagocytes contain tiny vesicles full of powerful digestive enzymes, which are actually
lysosomes. After the pathogen has been swallowed, these digestive enzymes break it down into small
units and destroy it. Phagocytes are kept very busy in the body, since they are constantly exposed to a
variety of potential pathogens from their environment. In an acute infection, millions of phagocytes
may die as they are trying to eliminate the pathogens. The dead phagocytes and pathogens accumulate
as pus in the tissues.
No matter how well phagocytes work, it will often happen that pathogens multiply faster than
the rate at which phagocytes are able to eliminate them. In this case, these diligent cleaning workers
share the job with lymphocytes. These are not specified in engulfing the pathogens, but in
immobilising them in various ways.
While phagocytes are on a constant patrol in the tissues, lymphocytes spend most of their life in
the lymph vessels, accumulating in large numbers in the lymph nodes. Here, they look out for those
phagocytes which have met and engulfed an antigen. It is the phagocytes that activate the lymphocytes
by showing them part of the swallowed antigen. However, the action the latter take depends on what
type of lymphocyte they are. Besides the lymph nodes, there are various lymph tissues throughout the
body, which are meeting point for white blood cells. These include the tonsils, the plaques of the
intestines, the appendix and the spleen. (The spleen, located below the left lung, also serves as a blood
storage facility and as decomposer of old red blood cells.)
B lymphocytes are born in the bone marrow, and stay there for further maturation. Later,
however, they enter the lymph circulation and gather in the lymph nodes, where their chances of
meeting an antigen are the highest. Having detected an antigen, B cells differentiate into plasma cells,
and begin to produce antibodies. These antibodies are soluble, and are quickly carried around the body
inside the lymph and the blood. An antibody molecule has the ability to attach itself to a still mobile
antigen and immobilise the pathogen to which the antigen belongs. An immobilised pathogen is no
23
longer infectious, nor alive. Later, phagocytes easily clean these deactivated pathogens away. (See Fig
12.3)
T lymphocytes are produced in the bone marrow, but for further development, they are carried
to the thymus, a gland situated behind our breastbone. When they are mature, however, they also enter
the lymph vessels, and gather in the lymph nodes. Some T cells (the cytotoxic T cells) are responsible
for destroying our own virus-infected cells which are the factories of would-be virus particles.
Another type of T cell (the helpers) plays a central role in coordinating the actions of the immune
system. Without the helpers, other lymphocytes are not activated, and no antibodies are produced.
Deficiency of these T cells is what results in such unfortunate and fatal processes as we can see in
patients with AIDS.
Immune processes are often accompanied by fever. Fever is a condition of higher than normal
body temperature, which is set by the hypothalamus most often in response to an intrusion by a
pathogen. Fever helps destroying pathogens by denaturing their proteins. The substances that stimulate
the hypothalamus include bacterial metabolites or hormone-like molecules produced by white blood
cells.
Questions and exercises
1.
Write the number of the parts in Fig. 12.3.
after
these
words:
nucleus
(__),
cell
1
6
4
membrane (__), receptor molecule (__),
antibody molecule (__), bacterial antigen
5
(__), bacterium cell (__), digestive vesicles
(lysosomes) (__).
2.
Answer the following questions:
a.
Where can pathogens enter the body?
b.
What is an antigen?
c.
How
do
phagocytes
deal
7
with
pathogens?
2
d.
What is pus?
e.
What are the two types of lymphocytes?
Fig. 12.3 A phagocyte engulfing a bacterium (from
f.
Where do B lymphocytes develop?
courses.washington.edu/physeng/bloodcells/phagocytosis.htm)
g.
What is the function of the two groups of T lymphocytes?
12.1.2.1 An immune response
Let’s see step by step how the immune system eliminates a pathogen during an immune response (see
Fig 12.4). In the first step, a phagocyte detects and engulfs an antigen, a fragment of which it displays
to T helper lymphocytes, thus activating them. In the second step, these T cells further activate both B
cells and cytotoxic T cells. In the third step, B lymphocytes begin producing antibodies, which bind to
antigens, and immobilise them. Also, cytotoxic T cells do their job by killing the body’s own infected
cells. Finally, phagocytes clear away the dead pathogens and the remains of dead body cells. But this
is not all that makes an immune response so effective.
3
24
NOTES
MHC II : a phagocyte’s receptor molecule
that identifies and binds to a T helper cell.
MHC II only binds to a T cell if the
phagocyte has already engulfed and digested
an antigen, and has attached a fragment of it
(epitope) to MHC II.
CD4: a T helper’s signal molecule
CD8: a cytotoxic T cell’s signal molecule
TCR: T cell receptor for binding an MHC
II–antigen epitope complex.
APC: Atypical phagocyte cell
Cytokines:
hormone-like
substances
produced to activate lymphocytes.
Fig 12.4 General layout of an immune response (from connection.lww.com/Products/porth7e/Ch19.asp)
Both B and T lymphocytes have a most peculiar ability that distinguishes them from all other cells of
the body. When activated, they divide at an incredible rate, faster than most pathogens reproduce. This
time, it is very important that the daughter cells are exactly the same as the parent cells. In other
words, rapid cloning takes place. In this way, lymphocytes are able to present a huge army of cells,
specialised in stunning and killing exactly that type of pathogen which has attacked the body.
War, as always, is a risk. If the precisely coordinated legion of white blood cells reproduce and
get activated faster, they take the upper hand, and the pathogen has no chance for survival. In some
cases, however, the pathogen wins the war, and the body may be destroyed. This may happen when
the immune system is weak or deficient. Some pathogens can ‘outsmart’ the defensive system in a
way or another, for instance by reproducing faster, or by producing toxins. This is also very dangerous,
25
unless help (such as an antibiotic) is given. In other cases still, the pathogen lodges itself in the body
and utilises its resources for its own use, and a status quo is reached, leaving the parasite in the body,
while letting the body stay alive.
The immune system has yet another peculiar characteristic, the production of memory cells.
After an immune response has taken place, each lymphocyte produces a memory cell as one of its
clones. In another infection by the same pathogen, the memory cells will remember that they have met
this pathogen before, and will be able to take action more quickly. The importance of memory cells
can be easily seen if we consider the following: The first time a pathogen enters the body, it makes us
ill, because in the initial stages of an immune response it breeds more quickly than our white blood
cells do. Later, however, our cells take the upper hand, and eliminate the intruders. A second time the
same pathogen enters, there are already memory cells in the lymph. The immune response is faster so
we do not get ill. This leads us to understanding how vaccination works.
Questions and exercises
1.
Answer these questions:
a.
How does an immune response begin?
b.
What role do T helpers play in an immune response?
c.
Why do lymphocytes need to clone?
d.
How many types of clones are made?
e.
How can pathogens make it difficult for the immune system to defeat them?
f.
What is the function of memory cells?
12.1.2.2 Types of immunity
People are not defenceless against diseases. Bacterial diseases can usually be treated using antibiotics.
Viruses are very often eliminated by the immune system, and no medicine needs to be given. If a virus
is especially difficult to defeat, medicines are still applied to block its life cycle. Another method is
prevention, which is usually done using vaccination.
Questions and exercises
1.
Below you can read about several types of immunity. Match one of the following items to each
paragraph below: (1) natural active immunity, (2) natural passive immunity, (3) artificial active
immunity, (4) artificial passive immunity. One item can be matched to two paragraphs.
A. After a disease, the memory cells of your immune system will remember the pathogen, and
the next time it penetrates into the body, it will be a lot easier to defeat it. ___
B. Foetuses receive antibodies from their mothers through the placenta. Newborn babies get
antibodies in the milk. ___
C. When you cut or pierce yourself deeply with a rusty or dirty object, Tetanus bacteria may enter
your body. Their toxin can cause a fatal condition by getting your muscles in a state of cramp.
This can result in the paralysis of breathing muscles, which leads to death. To prevent this
from happening, doctors give you an antitetanus jab, which contains specific antibodies
against the Tetanus toxin. These immobilise the toxin probably present, and you will be saved.
(This treatment is usually supported by another one later: you might be given an injection
containing weakened bacteria to develop active immunity.) ___
26
D. You can be injected with live but weakened bacteria or viruses. The pathogens in these
injections do not harm the body, but their antigens trigger an immune response, which results
in the production of memory cells. So, the next time the pathogens enter the body (this time
‘real’ ones), the body will know how to defend against them. You get such weakened
pathogens in a TB (tuberculosis) or a rubella vaccination. TB is a really dangerous and slowly
progressing disease of the lungs. Some people have a natural resistance to this disease, so
before a vaccination is given, you are tested to check this. Rubella is not a dangerous disease,
except to foetuses. This is why vaccinations are given only to teenage girls. ___
E. Sometimes it is better to get injected with killed bacteria or viruses, such as in case of
whooping cough. While whooping cough is unpleasant because of the constant coughing, the
disease also involves dangers of permanent brain damage as a condition afterwards. In
diphtheria, which still used to be dangerous back in the 19th century, the air passages could be
blocked owing to an overproduction of toxic mucus. Vaccination, which contains the
modified toxin of the bacterium, managed to put an end to it. The injection is still given,
more than once during childhood. When vaccinating against hepatitis B, doctors inject part of
the virus in the body. This part is a very active antigen. ___
12.1.2.3 Health issues
Questions and exercises
1.
The following text is about antibiotics (from http://familydoctor.org/680.xml). Fill in the gaps with an
item from this list: resistant, symptoms, coughs, bacteria, growing, medicines, infections, not yet,
viral, lungs, mucus.
Antibiotics: When They Can and Can't Help
What are antibiotics?
Antibiotics are strong _________________ that can stop some infections and save lives. But
antibiotics can cause more harm than good when they aren't used the right way. You can protect
yourself and your family by knowing when you should use antibiotics and when you shouldn't.
Do antibiotics work against all infections?
No. Antibiotics only work against infections caused by _________________. They don't work
against any _________________ caused by viruses. Viruses cause colds, the flu, and most
_________________ and sore throats.
What is "bacterial resistance"?
Usually antibiotics kill bacteria or stop them from _________________. However, some bacteria
have become _________________ to specific antibiotics. This means that the antibiotics don’t
work against them. Bacteria become resistant more quickly when antibiotics are used too often or
are not used correctly.
Resistant bacteria sometimes can be treated with different antibiotics to which the bacteria have
_________________ become resistant. These medicines may have to be given intravenously
(through a vein) in a hospital. A few kinds of resistant bacteria are untreatable.
What can I do to help myself and my family?
Don't expect antibiotics to cure every illness. Don't take antibiotics for _________________
illnesses like colds or the flu. Often, the best thing you can do is let colds and the flu run their
course. Sometimes this can take 2 weeks or more. If your illness gets worse after 2 weeks, talk to
your doctor. He or she can also give you advice on what you can do to ease your
_________________ while your body fights off the virus.
27
How do I know when I need antibiotics?
The answer depends on what is causing your infection. The following are some basic guidelines:
 Colds and flu. Viruses cause these illnesses. They can't be cured with antibiotics.
 Cough or bronchitis. Viruses almost always cause these. However, if you have a problem with
your _________________ or an illness that lasts a long time, bacteria may actually be the
cause. Your doctor may decide to try using an antibiotic.
 Sore throat. Most sore throats are caused by viruses and don't need antibiotics. However, strep
throat [sore throat caused by Streptococcus bacteria] is caused by bacteria. Usually you'll have a throat
swab [a sample of mucus taken from your throat] and a lab test before your doctor will prescribe an
antibiotic for strep throat.
 Ear infections. There are several types of ear infections. Antibiotics are used for some, but not
all, ear infections.
 Sinus [cavities of the face] infections. Antibiotics are often used to treat sinus
infections. However, a runny nose and yellow or green _________________ do not necessarily
mean you need an antibiotic.
2.
When is it necessary to reduce fever? What methods are available to do that?
3.
Who were Louis Pasteur and Ignaz Semmelweis? Why is their professional contribution to medical
science important?
12.1.2.4 Problems with the immune system
Questions and exercises
1.
A very interesting example of how the immune system reacts to an antigen is that of blood
transfusion. Read the text below (from http://anthro.palomar.edu/blood/ABO_system.htm) and answer
the questions that follow.
ABO Blood Types
The most well known and medically important blood types are in the ABO group. They were discovered
in 1900 and 1901 at the University of Vienna by Karl Landsteiner in the process of trying to learn why
blood transfusions sometimes cause death and at other times save a patient. In 1930, he belatedly
received the Nobel Prize for this discovery.
Fig 12.5 Human blood groups, antibodies and antigens (from en.wikipedia.org/wiki/Image:ABO_blood_type.svg)
28
All humans and many other primates can be typed for the ABO blood group. There are four principal
types: A, B, AB, and O. There are two antigens and two antibodies that are mostly responsible for the
ABO types. The specific combination of these four components determines an individual's type in most
cases. The table below shows the possible permutations of antigens and antibodies with the
corresponding ABO type [….]
For example, people with type A blood will have the A antigen on the surface of their red cells (as shown
in the table below). As a result, anti-A antibodies will not be produced by them because they would cause
the destruction of their own blood. However, if B type blood is injected into their systems, anti-B
antibodies [already present] in their plasma will recognize it as alien and burst or agglutinate the introduced
red cells in order to cleanse the blood of alien protein.
ABO
Blood Type
A
B
O
AB
Antigen
A
Antigen
B
Antibody Antibody
anti-A
Anti-B
yes
no
no
yes
no
yes
no
yes
no
yes
yes
no
yes
no
yes
no
Individuals with type O blood do not produce ABO antigens. Therefore, their blood normally will not be
rejected when it is given to others with different ABO types. As a result, type O people are universal
donors for transfusions, but they can receive only type O blood themselves. Those who have type AB
blood do not make any ABO antibodies. Their blood does not discriminate against any other ABO type.
Consequently, they are universal receivers for transfusions, but their blood will be agglutinated when given
to people with every other type because they produce both kinds of antigens.
ABO
Blood Type
A
B
O
AB
Antigen
A
Antigen
B
Antibody Antibody
anti-A
Anti-B
yes
no
no
yes
no
yes
no
yes
no
yes
yes
no
yes
no
yes
no
It is easy and inexpensive to determine an individual's ABO type from a few drops of blood. A serum
containing anti-A antibodies is mixed with some of the blood. Another serum with anti-B antibodies is
mixed with the remaining sample. Whether or not agglutination occurs in either sample indicates the
ABO type. It is a simple process of elimination of the possibilities. For instance, if an individual's blood
sample is agglutinated by the anti-A antibody, but not the anti-B antibody, it means that the A antigen is
present but not the B antigen. Therefore, the blood type is A.
a.
b.
c.
d.
What antibodies are present in type AB blood?
What antigens are found in the cell surface membrane of the red blood cells in a blood type 0
person?
Who is a universal donor? Why?
The rhesus (Rh) system of blood grouping was first discovered in the blood of the rhesus
monkey. About 85% of the people in the world have red blood cells carrying the rhesus factor
29
on their cell membrane. They are therefore Rh+. Rh- individuals do not carry anti-Rh antibodies
in their blood plasma, but they can quickly manufacture them when exposed to Rh + cells.
Besides in blood transfusions, the Rh factor causes a problem in Rh- women during their second
pregnancy. This phenomenon is called Rh intolerance. What do you think it means? (Consider
that the antibodies may pass across the placenta.)
2.
Sometimes, there may be problems with the immune system. Read the following passage (from
Pickering: Complete biology, p. 299) and underline the best alternatives.
The activity of the immune system saves all our lives, many times over. There are occasions, however,
when it may actually increase / reduce the likelihood of survival. These are described below.
Autoimmune diseases are caused by the body producing antibodies / antigens which destroy its own
cells. Why this should happen is not known. Examples include:


diabetes – underactive pancreatic / thyroid gland – the body destroys its own insulin-producing
cells by an immune reaction
rheumatoid arthritis – white blood cells destroy epithelial / cartilage tissue in joints and make
movement extremely painful.
Allergies are conditions in which the body becomes insensitive / sensitive to a substance and over-reacts
to it. This may cause swelling and tissue damage. Examples include straw / hay fever and sensitivity to
bee and wasp stings. Allergies are treated with drugs such as antihistamines to reduce the immune
response.
Transplant rejection – the most common organ transplant in Britain is the spleen / kidney transplant,
but heart, intestine, lung, liver and pancreas transplants are becoming more common. The recipient’s
lymphocytes / red blood cells may recognise antigens on the surface of the donor organ as foreign and
slowly destroy it. This problem of rejection is being overcome by:
 drugs that stimulate / suppress the immune system of the recipient long enough to allow the
transplanted organ to become established
 matching tissues wherever possible, for example by seeking out relatives of people needing
bone marrow transplants, since relatives are more likely to have similar / different antigens to
the recipient.
2.
3.
Do you think there can be a connection between environmental pollution and allergies? If so, what?
Read the following text about cancer (based on Kropog et al.: Biológia feladatgyűjtemény, pp 76-77), and
answer the questions that follow.
A common feature of all types of cancer is excessive and uncontrolled cell division. Healthy cells
divide from time to time, and the genetic schedule of cell division is coded in the DNA. Sometimes
the structure of DNA can alter as a result of a change in environmental factors such as radiation, viral
infection, malnutrition, or certain chemical compounds, and cell division is set loose. Malignant cell
multiplication uses up so much energy in the end that the body runs out of its resources and dies.
Mutant cells that are produced during the course of such uncontrolled cell division develop
into a tumour, unless destroyed by the immune system. However, not all tumours are dangerous. There
are two types of them: benign tumours and malignant tumours. Although both a result of uncontrolled cell
division, benign tumours are covered by a capsule of connective tissue, and although they can grow
very big (some smooth muscle tumours may weigh many pounds in later stages), this keeps them
from invading other body tissues. Benign tumours only need to be removed if they cause a problem
by pressing on organs.
Malignant tumours, however, may grow very quickly, with cells dividing almost every 24 hours.
The tumour proliferates, and infiltrates the neighbouring tissues. Later, when tumour cells enter the
blood and lymph vessels, they get carried to more distant parts of the body, they adhere there and
start to grow, which causes secondary tumours (metastases) to appear.
The biggest risk factor in cancer is age. This is probably because both the tissues and the
immune system become weaker with age. Many experts claim that free radicals (reactive derivatives of
the water molecule produced by radiation and chemicals) that damage the DNA are mostly in charge
30
for the worse condition of tissues. Also, the lack of important nutrients is said to contribute greatly to
the formation of tumours. This, however, does not mean that cancer is a disease of old age. While
many people do not develop cancer even when they are old, some others can do so when they are still
younger. Testicular cancer, for instance, typically appears in men between 19 and 44. Some cancer
types, such as leukaemia, brain cancer or bone cancer, are the most common in children. Recently,
there has been a great advancement in treating childhood cancer. Ten years ago, only about 10% of
children with leukaemia were cured, as opposed to the 75% of today.
A saddening fact is that in the developed world, cancer takes an increasingly higher death toll.
In the USA today, cancer accounts for approx. 25% of all deaths, and about 0.5% of the population is
diagnosed with cancer each year. In Hungary, 5400 people died in the 1920s, more than 10,000 in the
1940s, and this number has risen to 33,000 recently. Hungary, unfortunately, is a leader in the number
of deaths yearly. According to the tendency, about every second or third person in the world will
develop a malignant tumour in some stage of their life in the near future.
Cancer affects men and women alike. While most women are diagnosed with breast cancer,
most cases of lung cancer are discovered in men.
Predisposition to cancer has serious genetic background, but it is the interaction between
genetic and environmental factors that lead to the formation of tumours. Therefore, the risk of cancer
can be greatly reduced by conducting a healthy lifestyle.
Organs that are most frequently affected by cancer include the stomach and intestines, whose
recovery rate is about 35%. It is smokers that primarily fall victim to lung cancer, the recovery rate of
which is only 10%. Every 12th woman will develop breast cancer, and 60% of them will recover from
the disease. Most skin cancers that are early detected will have a 90% recovery rate. Bladder and
prostate cancer heal at the rate of 60 and 45% respectively, due to proper treatment.
If a cancerous tumour is detected and removed before it has infiltrated the nearby tissues, and
the patient has no signs of metastasis, the patient is cured, and the disease is not likely to recur.
However, most cancers are discovered later, when they have probably already formed metastases. In
this case, surgeons remove the greatest tumours, and oncologists usually administer chemotherapy
(the infusion of poisonous chemicals that kill tumour cells) to kill smaller, secondary tumours. Time is
a crucial factor in discovering tumours – the chances of curing cancer are a lot higher when they are
detected in early stages. Although signs of cancer can indicate different, often harmless, diseases, it is
advisable to consult a doctor when: 1) there is blood in the faeces accompanied by cramps of the
intestines and a remarkable weight loss; 2) you discover wounds that do not heal; 3) you palpate nodes
on the skin, in the breast, or in the testes; 3) you have a constant higher temperature that does not
drop back to normal or inflammations that do not respond to any regular treatment; 4) you feel
unusually weak for a while.
In quite a few cases, clinical therapy (surgery, chemotherapy or radiotherapy – the irradiation of
the tumour with radioactive rays that destroy it) fails to work. In these cases still, there are very
successful alternative possibilities. Some diets (rich in organic fruits and vegetables) have proved to be
extremely useful in curing cancer, as well as phytotherapy (the use of herb teas). Very high doses of
intravenous vitamin C have successfully decreased the number and size of tumours in the majority of
patients. Naturally, alternative therapies can be used as supplementary to clinical treatment any time.
a.
b.
c.
d.
e.
f.
g.
h.
i.
What is the cause of tumour formation on the cellular level?
What is the difference between benign and malignant tumours?
Why is age probably the most important risk factor?
Is cancer inherited?
How has the number of new cases of cancer changed in the developed world recently?
How can you lower the chances of cancer?
Which type of cancer can be best cured?
What are some possible signs of cancer? What is important to do when someone has detected
one of some of these signs?
How is cancer usually treated? Are there alternative methods?
31
Chapter Revision
1.
2.
3.
4.
5.
6.
7.
8.
What are the two main functions of the excretory system?
What role do the following organs play: ureter, kidney, bladder?
Write a sentence about how the following events occur along the length of a nephron: filtration,
excretion, reabsorption.
How do ADH and aldosterone work?
What are the basic functions of the elements of the skeletal system?
Where are blood cells made?
Which structure of the bone covers and nourishes it?
Which bone does each paragraph below describe?
a.
b.
c.
d.
e.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
These are connected to the sternum in the front and to the backbone in the back.
_________________
These are the longest bones in the body; their fracture is often fatal in old age.
_________________
These are situated between the tarsals and phalanges. _________________
Situated inside the pectoral girdle, these bones link the scapulae to the sternum on each side.
_________________
This is the largest bone of the cranium. _________________
What is the function of intervertebral disks?
What is the difference between a hinge joint and a ball-and-socket joint?
What is the function of the synovial membrane? And that of the cartilage at the epiphysis?
What is the basic difference between a dislocation and a sprain?
How does the skin protect from pathogens?
How does a blood clot form? What are the biochemical steps that lead to fibrin formation?
What is the function of phagocytes? How do they trigger an immune response?
What role do B lymphocytes play in an immune response?
How many types of T cells do you know? What is their function?
What immunity do vaccines give? How are they made?
Do antibiotics work against viruses? Why / why not?
Can a person with blood type A donate blood to a person with blood type O? Why / why not?
What are the causes of tissue rejection? How can it be avoided?