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OCR AS Biology Unit 2 Module 2: Food and Health
Health and Disease OCR AS Biology Unit 2 Module 2: Food and Health
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Learning Outcomes Discuss what is meant by the terms health and disease Define and discuss the meanings of the terms parasite and pathogen
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What is health? “health is more than just the absence of disease”
What is meant by health? What is meant by disease? Health absence of disease Disease disorder of a systems normal functions
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What is health? You have been given 6 case studies In your groups
discuss the health of each individual Rank them from 1 – 6 1 healthiest 6 unhealthiest Remember you must be able to give reasons for your choices
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Definitions Health Disease
A state of complete physical, mental and social well-being, which is more than just the absence of disease. Disease A problem with mind or body leading to a departure from good health.
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Good Health Free from disease
Able to carry out mental and physical tasks expected by society Well fed, balanced diet Housing and sanitation Happy and positive outlook Well integrated into society
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The Health Triangle Physical health means the health of the body
Mental health means the health of the mind. Social health means forming good relationships.
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The Health Triangle Physical Social Mental
If you take any of these away - the triangle collapses
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What is health? In your groups Go back to the original 6 case studies
Have your opinions changes Rank them from 1 – 6 1 healthiest 6 unhealthiest Remember you must be able to give reasons for your choices
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Disease There are nine broad overlapping categories of disease (see handout) Diseases can also be grouped into Single cause e.g. malaria Multifactorial e.g. heart disease
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Disease Acute Sudden rapid changes and lasting for a short time Chronic Long term – debilitating Develops slowly and persists
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pathogen Infectious diseases are diseases caused by pathogens.
A pathogen is defined as an organism which causes disease Lives by taking nutrition from the host May cause damage to the host Disease transmission is the transfer of a pathogen from infected to uninfected people
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Parasite A parasite is defined as
Organisms that live in or on another living things Benefit at the hosts expense Can be Internal parasite e.g. tapeworm External parasite e.g. head louse
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Infectious Disease Organisms that can cause infectious disease include
Bacteria e.g. cholera and TB Fungi e.g. athlete’s foot and ringworm Virus e.g. cold, influenza and AIDS Protoctista e.g. amoeboid dysentery, malaria
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Learning Outcomes Describe the causes and means of transmission of malaria, AIDS/HIV and TB (symptoms not required) Describe the global impact of malaria, AIDS/HIV and TB
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Infectious diseases A pathogen can: Gain entry to the host
Colonize the tissues of the host Resist the defences of the host Cause damage to host tissues
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Transmission The most common forms of transmission are
By means of a vector By physical contact By droplet infection Malaria and tuberculosis Pathogens invade cells and spread through the tissues HIV Virus can lie dormant in T lymphocytes Weakens the immune system to opportunistic infections (AIDS)
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Malaria Causative organism Protoctista genus Plasmodium
P. falciparum is the most widespread Methods of transmission insect vector Female Anopheles mosquito See diagram Global distribution Widely distributed through the tropics and sub tropics Annual incidence 300 million Annual mortality worldwide 1.5 – 1.7 million
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Malaria Global impact Control measures
Increasing drug resistance by Plasmodium 40% of world’s population live in malarial areas Difficulty in developing a vaccine Increase in epidemics as environmental and climatic changes favour mosquitoes Mosquitoes are developing resistance to insecticides Control measures Use sleeping nets to prevent mosquitoes biting at night Use of drugs to fight of Plasmodium Reduce mosquito populations drain marshes and swamps destroy mosquito larva – oil or insecticide on water, use carnivorous fish
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TB (tuberculosis) Causative organism Mycobacterium tuberculosis
Mycobacterium bovis Methods of transmission inhalation of droplets from infected person via infected milk Global distribution Worldwide in developing countries and among migrants and inner cities in developed countries 8.8 million new cases every year 1.5 million deaths
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TB (tuberculosis) Global impact Control measures
Some strains are resistant to drugs (1950’s) AIDS pandemic Poor housing and rising homelessness Breakdown of TB control programmes Control measures Contact tracing, through testing for bacteria and screening for symptoms 2005 – BCG vaccine ruled ineffective DOTS (directly observed short course treatment) Long course of antibiotics
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HIV/AIDS Causative organism Human Immunodeficiency Virus
Methods of transmission Body fluids, esp. semen, vaginal fluids and blood Sexual intercourse, shared needles, child birth, breast feeding Infected blood products Global distribution World wide Highest prevalence in sub-Saharan Africa and South-east Asia
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HIV/AIDS Global impact Control measures
39.5 million people living with HIV 2006 4.9 million new cases 2.9 million deaths from AIDS Affects the affluent and the impoverished TB is an associated opportunistic infection Control measures Use of condoms Health education (safe sex) Screening of blood donations Heat treatment of blood products to kill viruses Needle exchange schemes Contact tracing
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Module 2: Food and Health Health and Disease
Immunity Module 2: Food and Health Health and Disease
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Learning Outcomes Define the terms immune response, antigen and antibody. Describe the primary defences against pathogens and parasites (including skin and mucous membranes) and outline their importance. Describe, with the aid of diagrams and photographs, the structure and mode of action of phagocytes.
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Definitions Immune response Antibodies Antigen
Specific response to a pathogen Involves the action of lymphocytes and the production of antibodies Antibodies Protein molecules produced and released in response to a antigen Antigen Foreign molecule – protein or glycoprotein Provokes an immune response
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Primary Defences The body’s primary defences attempt to stop pathogens from entering body tissues This includes The skin (epidermis) Mucous membranes Eyes protected with tears Ear canal lined with wax
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Epidermis The outer layer of the epidermis is a layer of dead cells which contain the fibrous protein keratin. These cells are produced in the process keratinisation – the cells dry out and the cytoplasm is replaced with keratin. This layer of cells acts as a barrier
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Mucous membranes Mucous membranes protect surfaces which are at risk of infection Mucus is secreted by the epithelial linings of airways, digestive system and reproductive systems In the airways ciliated cells move mucus up to the mouths where it can be swallowed In the stomach, hydrochloric acid kills most pathogens that we ingest.
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Secondary Defences Non-specific immune response
Phagocytes Specific Immune response B and T lymphocytes Antibody production
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Phagocytosis Phagocytes engulf and digest pathogenic cells Neutrophils
found in the blood and body tissues Collect at an area of infection Macrophages Travel in blood as monocytes settle into the lymph nodes where they develop Stimulates production of T lymphocytes
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Phagocyte - photographs
Neutrophil Macrophage Macrophage engulfing tuberculosis bacterium
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Stages in phagocytosis
Pathogens are recognised by antigens on their surface Phagocyte moves towards pathogen and receptors on the cell surface membrane attach to antigens on the pathogen Phagocyte engulfs the pathogen creating a phagosome Lysosomes fuse with the phagosome releasing digestive enzymes End products absorbed into the cytoplasm.
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Phagocytosis Animations
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Stages of Phagocytosis
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Learning Outcomes Describe the structure and mode of action of T lymphocytes and B lymphocytes, including the significance of cell signalling and the role of memory cells. Describe, with the aid of diagrams, the structure of antibodies. Outline the mode of action of antibodies, with reference to the neutralisation and agglutination of pathogens.
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Immune Response Immune response is the activation of lymphocytes in the blood to help fight disease T- Lymphocytes Produced in bone marrow Mature in the Thymus B-Lymphocytes Produced and matures in bone marrow
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Immune response Pathogen enters body Clonal selection Clonal expansion
Antigens bind to complementary glycoproteins on B and T lymphocytes This stimulate the immune response Clonal expansion B and T lymphocytes divide by mitosis
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T-lymphocytes T lymphocytes divide into 3 types of cell
T helper cells (Th) Release cytokines stimulate B cells to develop Stimulate phagocytosis (cell signalling) T killer cells (Tk) Attack and kill infected body cells T memory cells (Tm)
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B lymphocytes B lymphocytes develop into two types of cell
Plasma cells (P) Flow in blood Manufacture and release antibodies B memory cells (Bm) Immunological memory Remain in blood for a number of years Stimulate the production of plasma cells quickly upon reinfection by same pathogen.
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Cell signalling in immune response
Identification of pathogens Sending distress signals Antigen presentation Instructions Communication using cytokines
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Stages in immune response
Infection and reproduction of pathogen Presentation of antigens Clonal selection Clonal expansion Differentiation (proliferation) Action – antibody production
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Antibodies Proteins a.k.a. immunoglobulins
Specific shape complementary to that of an antigen Antibody shape 4 polypeptide chains held together by disulphide bridges Variable region 2 binding sites specific to an antigen Hinge regions allow flexibility
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Antibody structure
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Mode of action of antibodies
Neutralisation Antibodies bind to toxins neutralising their effects Antibodies combine to viruses and prevent them from entering the cell. Agglutination Pathogen clump together Too large to enter host cells Helps phagocyte to engulf and digest pathogens
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Learning outcome Compare and contrast the primary and secondary immune responses.
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Primary Immune response
Production of plasma cells Antibodies produced to combat infection Takes a few days for number of anti-bodies in blood to rise
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Secondary immune response
B memory cells circulate in blood Rapidly produce plasma cells upon reinfection Plasma cells produce antibodies Rapid response
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Primary and secondary immune response
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Learning Outcomes Compare and contrast active, passive, natural and artificial immunity. Explain how vaccination can control disease. Discuss the responses of governments and other organisations to the threat of new strains of influenza each year
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Immunity Natural immunity Artificial immunity Active immunity
gained as part of normal life processes Artificial immunity Gained by deliberate exposure to antibodies or antigens Active immunity Results from stimulation of immune response Passive immunity Introduction of antibodies Short lived
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Immunity Immunity Active Passive Natural Artificial
Long term immunity Infected by the disease inducing an immune response Takes time Immediate protection Antibodies from mother Across placenta In colostrum (breast milk) Short term immunity Artificial Immunisation or vaccination Injected with antibodies e.g. tetanus injections
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Vaccination Vaccine Preparation of antigen Injected or given by mouth
Stimulates primary immune response Boosters given to stimulate secondary immune response
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Antigenic material Living attenuated micro-organisms
Can not cause symptoms Multiply E.g. TB, poliomyelitis Dead micro-organisms Harmless but induce immunity E.g. typhoid, cholera Preparation of antigens E.g. hepatitis B vaccine Harmless toxin E.g. tetanus vaccine
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Control of disease Vaccinations can be used to control disease by providing immunity to all those at risk Herd immunity Use a vaccine to provide immunity to all of the population at risk Ring immunity Vaccinate everyone in surrounding area to prevent transmission of disease
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Influenza Viral disease of the respiratory system Associated with
Fever Sore throat Headache Muscle pains Weakness Can lead to pneumonia Can be fatal New strains arise by mutations (some virulent)
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vaccination programmes
Epidemic Disease suddenly spreads rapidly to infect many people Pandemic Large scale outbreak of a disease Governments research and try to predict which strains of flu are going to appear each year
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Vaccination programmes in UK
All people aged over 65 Young people with asthma People who work in high-risk categories such as medical professionals The strains of flu used in the immunisation programme change each year.
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Learning Outcomes Outline possible new sources of medicines, with reference to microorganisms and plants and the need to maintain biodiversity.
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New Medicines Why do we need new medicines
Pathogens become resistant to existing drugs e.g. antibiotics New disease emerge New vaccines needed e.g. HIV Existing vaccines can be improved
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Discovery of New Medicines
By accident E.g. Alexander Fleming and the discovery of penicillin Traditional medicine Anaesthetics Observation of wildlife Modern research
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Natural medicines Discovery of natural drugs has concentrated on tropical plants due to the great diversity of species in tropical rainforests Examples Madagascan periwinkle – anticancer Sweet wormwood – antimalarial It is important that plant species do not become extinct before we can discover their value.
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Module 2: Food and Health Health and Disease
Smoking and Disease Module 2: Food and Health Health and Disease
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Learning Outcome Describe the effects of smoking on the mammalian gas exchange system, with reference to the symptoms of chronic bronchitis, emphysema (chronic obstructive pulmonary disease) and lung cancer.
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Smoking - Intro WHO considers smoking to be an epidemic
Cigarette smoke contains Tar – a group of chemicals including carcinogens Carbon monoxide nicotine
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Reasons to give up smoking
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Short term effects of Tar
Tar settles in linings of airways and alveoli Inceases diffusion distance of gases Chemicals can cause an allergic reaction Lumen of airway narrows restricting air flow. Paralyses cilia Mucus secreting cells enlarge – produce more mucus Increase risk of infection
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Long term effects of tar
Smokers cough Irritation of airways Damages lining of airways and alveoli Lining replaced by scar tissue Smooth muscles thickens, lumen narrows and airflow is permanently restricted.
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Diseases linked with smoking
Chronic Obstructive Pulmonary disease Combination of diseases that includes Asthma Chronic bronchitis emphysema
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Chronic Obstructive Pulmonary Disease
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Chronic Bronchitis Inflamed lining Smooth muscle layer thickens
Goblet cells and mucus glands secrete more mucus Damage to cilia Symptoms Shortness of breath Wheezing Persistent cough Increase risk of lung infection
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Emphysema Loss of elasticity of alveoli Alveoli burst
Air spaces are larger reducing surface area for gas exchange Symptoms Shortness of breath Difficulty exhaling Blood less well oxygenated fatigue
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Lung Cancer Cigarette smoke contains carcinogenic compounds including benzopyrene Carcinogens enter cells of lung tissue Mutation affects the gene controlling cell division Uncontrolled cell division leads to a tumour Bronchi become blocked by cancerous growths
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Symptoms of lung cancer
persistent cough Coughing up blood Weight loss Pain in chest
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Learning Outcomes Describe the effects of nicotine and carbon monoxide in tobacco smoke on the cardiovascular system with reference to the course of events that lead to atherosclerosis, coronary heart disease and stroke.
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Nicotine and carbon monoxide
Nicotine and carbon monoxide pass from the lungs into the circulation Changes occur that can lead to Atherosclerosis Coronary heart disease stroke
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Nicotine Addictive drug stimulant
Releases adrenaline which increases heart rate and blood pressure Stimulates decrease in blood flow to extremities Increases chance of blood clots Makes platelets sticky
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Carbon monoxide Enters red blood cells and combines with haemoglobin to form carboxyhaemoglobin Reduces oxygen carrying capacity of the blood Damages linings of arteries
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Cardiovascular disease
Multifactorial There is a number of risk factors Of which smoking is just one Degenerative disease of the heart and circulatory systems 20% death worldwide Up to 50% developed countries
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Atherosclerosis Atherosclerosis
Accumulation of fatty material (atheroma) in artery walls, reducing flow of blood to the tissues Reduces the size of the lumen Reduces blood flow
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Definitions Atheroma Plaques
Contains cholesterol, fibres, dead muscle cells and platelets Plaques Build up of atheroma Make arteries less elastic and reduce the flow of blood
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atherosclerosis
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Stages in development of Atherosclerosis
Damage to endothelium of arteries invasion of phagocytes to repair damage Secretions from phagocytes stimulate growth of smooth muscle and the accumulation of cholesterol Atheroma builds up Atheroma forms plaque Size of lumen reduced, Blood flow reduced
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Stages in atherosclerosis
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Thrombosis Blood flow past the plaque is not smooth which increases the risk of blood clotting. Thrombus Blood clot in artery which stops flow May dislodge and be carried in the blood
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Coronary heart Disease
Lumen of coronary arteries narrowed by plaque Reduces the blood flow to heart muscles 3 forms Angina Heart attack / myocardial infarction Heart failure
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Stroke Death of part of the brain Can be sudden Two causes Thrombus
Blood clot blocks a narrow artery in the brain Haemorrhage an artery leading to the brain burst Aneurysm = weakness in wall of artery
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Learning Outcomes Evaluate the epidemiological and experimental evidence linking cigarette smoking to disease and early death.
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Epidemiology The study of the distribution of diseases in order to find a means of preventing and controlling it. Epidemiological studies Identify links between disease and risk factors Identifies which countries / age range / gender may be at greater risk.
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Epidemiological studies
Information gained can be used to: Target funding Target research Target screening Target education and advice Predict future incidences of the disease
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Smoking and diseae 1950’s doctors first noticed a correlation between lung cancer and smoking. About half of smokers die of smoking related diseases Smokers are three times more likely to die in middle age than non-smokers
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Linking smoking to lung cancer
if stop smoking the risk of lung cancer decreases Smokers 18 times more likely to develop lung cancer than non smokers 25% smokers die due to lung cancer
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Linking smoking to lung diseases
98% emphysema sufferers are smokers 20% smokers suffer emphysema smokers twice as likely to die from pneumonia and influenza COPD is rare in non smokers
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Linking smoking to CVD This is less evident as CVD are multifactorial
However, substances in cigarette smoke can influence the cardiovascular system and likely to enhance atherosclerosis
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IMPORTANT POINT All conclusions drawn by epidemiological data show an association and not a causal link.
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Experimental Evidence - Dogs
Dogs exposed to unfiltered smoke developed changes similar to COPD and early signs of lung cancer. Dogs smoking filtered cigarette smoke developed changes which can lead to lung cancer
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Experimental evidence - Tar
Chemical analysis of tar shows that it contains known carcinogens When painted onto the bare skin in rats the tar caused cancer in the skin cells.
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