1. Gas Exchange And Smoking
Biology AS level

2. THE LUNGS

3. Distribution in The Lungs

4. Function of Parts Name Function Location Cartilage
Keeps the airways open and air resistance low, and prevents them from collapsing or bursting as the air pressure changes during breathing.
Trachea and Bronchus
Cilia
Carries the mucus upwards towards the larynx.
Trachea, Bronchus, Bronchiole
Goblet Cells
An epithelial cell that secretes mucus.
Mucous Glands
Located beneath the the epithelium, it secretes mucus too.
Smooth Muscle
Contract or relax to adjust the diameter of the airways.
Trachea, Bronchus and Bronchiole.
Elastic Fibre
Stretch during breathing and recoil during expiration to help force out air.
Alveolar Walls

5. Questions and Answers

6. Tobacco Smoke
Composed of mainstream smoke (from the filter or mouth end) or side stream smoke (from the burning tip) .
The main component of cigarette smoke that pose a threat to human health are
Tar
Carbon Monoxide
Nicotine
Tar and carcinogens damage the gas exchange system; carbon monoxide and nicotine damage the cardiovascular system.

7. Lung Diseases (Chronic Bronchitis)
Results in an accumulation of mucus in the bronchial passages. Therefore the mucus remains stuck in the lungs. Bacteria and virus accumulate and breed in the mucus.
Thickening of airways causing it to be narrower due to damaged epithelia being replaced by scar tissue, hence resulting in difficulty breathing.
Tar in cigarette smoke :
stimulates goblet cells and mucous glands to enlarge and secrete more mucus.
Inhibits the cleaning action of the ciliated epithelium that lines the airways.
Destroys many cilia and weakens the sweeping action of those that remains.
This damage and obstruction of the airways is chronic bronchitis. Sufferers have severe cough, producing large quantities of phlegm.

8. Lung Diseases (Emphysema)
Smoking causes inflammation in the lungs.
This involves the presence of increased numbers of white blood cells, some of which secrete chemicals that damage elastic fibers.
This makes the alveoli less elastic.
They may burst, resulting in larger air spaces. This reduces the surface area available for gas exchange.
The loss of elastin also makes it more difficult to force air out of the lungs when breathing out.
Results in shortness of breathe.

9. In summary, below are the changes that occur in the lungs of people with chronic bronchitis and emphysema.
Emphysema: digestion by phagocytes of pathways through alveolar walls; loss of elastin; overextension and bursting of alveoli to form large air spaces; decrease in surface area for gas exchange; lack of recoiling of air spaces when breathing out; decrease in volume of air forced our from lungs; shortness of breath.
Bronchitis : enlargement of mucous glands in airways; increased secretion of mucus; narrowing/obstruction of airways; inflammation; severe coughing; coughing up phlegm.

10. Lung Cancer
The most common symptoms of lung cancer is coughing up blood, chest pain and difficulty breathing.
Tumours in the lungs are located by one of three method :
Bronchoscopy
Chest X-ray
CT scan
Tar contains several substances that are carcinogens.
These react, directly or via breakdown products, with DNA in epithelial cells to produce mutations, which then leads to tumour.
It spreads through the bronchial epithelium and enter the lymphatic tissues in the lungs. It may metastasis and secondary tumour may established. This tumour is known as malignant.

11. Summary: The effect of tobacco on the gas exchange system.
Tar: paralyses or destroys cilia; stimulates oversecretion of mucus;leads to the development of bronchitis and emphysema
Carcinogens: cause changes in the DNA of cells in the bronchial epithelium, leading the development of bronchial carcinoma – lung cancer
Summary: Signs and Symptoms of COPD and Lung Cancer
COPD Signs : constant coughing (Smoker’s cough), coughing up lots of phlegm, breathlessness, wheezing
COPD Symtoms: tiredness, tighness of the chest
Lung cancer signs: coughing up blood; shortness of breath;.
Lung cancer symptoms: chest and shoulder pain. In 25% of cases there are no signs or symptoms, and the cancer is discovered in a chest X-ray or scan.

12. Effects of Nicotine on the Cardiovascular System
Smoking is just one among several risk factors that increase the chances of developing one of the cardiovascular diseases.
Nicotine is the drug in tobacco that is absorbed very readily by the blood.
It stimulates the nervous system to reduce the diameter of the arterioles and to release the hormone adrenaline from the adrenal glands.
As a result, heart rate and blood pressure increase and there is a decrease in blood supply to the extremities of the body, such as hand and feet, reducing their supply of oxygen.
Cardiovascular Diseases are diseases of the heart and circulatory system, such as coronary heart disease (CHD). Nicotine is a highly addictive drug that influences reward centers in the brain. It stimulates nerve endings in brain to release the transmitter substance dopamine, which is associated with pleasurable experiences. This makes it very hard to give up smoking.

13. Effects of Carbon Monoxide on the Cardiovascular System
Carbon Monoxide bind with hemoglobin to form the stable compound carboxyhaemoglobin.
Less oxygen is supplied to the heart muscle, putting a strain on it especially when the heart rate increase during exercise.
Carbon monoxide may also damage the linings of the arteries.

14. Atherosclerosis
Endothelium becomes damaged (e.g. due to high blood pressure, or cigarette smoke)
Damage causes inflammatory response. White blood cells move into the artery wall, and chemicals (cholesterol) from the blood accumulate. A deposit then builds up called an atheroma.
Calcium salts and fibrous tissue build up at site and form a hard swelling (plaque), making the artery lose some of its elasticity (hardens) and causing it to narrow.
Plaque makes it difficult for the heart to pump blood around the body and results in high blood pressure. Positive feedback results as the increased blood pressure makes it more likely that more plaques will form.
and

15. Coronary Heart Disease
Two coronary arteries branched from the aorta to supply all the muscles of the atria and the ventricles of the heart.
There are three forms of of CHD.
Angina Pectoris: severe chest pain brought on by exertion. Caused by severe shortage of blood to the heart muscle, but there is no death of heart tissue.
Heart Attack (Myocardial Infarction) : A moderately large branch of a coronary heart is obstructed by a blood clot, part of the heart muscle is starved of oxygen and dies. This causes sudden and severe chest pain.
Heart Failure : Due to the blockage of a mian coronary artery and the resulting gradual damage to heart muscle. The heart weakens and fail to pump efficiently.

16. Stroke
Occurs when an artery in the brain burst, so that blood leaks into brain tissue.
Also happens when there is a blockage in a brain artery due to atherosclerosis or a thrombus. The brain tissue in the area supplied by the artery is starved of oxygen and dies (cerebral infarction)
Normal brain
Brain After Stroke

17. Summary : Effect of Tobacco Smoke on the Cardiovascular System
Summary : Changes in the heart that leads to a heart attack
A break in the wall of the coronary artery; invasion by phagocytes; build-up of cholesterol; growth of smooth muscle; atherosclerosis; blood flow through artery is reduced; blood clots at site of atheroma; blood cannot supply oxygen and nutrients to heart muscle; heart muscle dies; myocardial infarction (heart attack).
Summary : Effect of Tobacco Smoke on the Cardiovascular System
Carbon monoxide: combines with haemoglobin to form the stable compound carboxyhaemoglobin, with the result that less oxygen is transported in the blood.
Nicotine: raises blood pressure; raises heart rate; increases likelihood of thrombosis; decreases blood supply to the extremities.
Both substances increase the rate at which atherosclerosis occurs in the walls of arteries. This makes smoking a risk factor in the development of CHD and stroke.

18. Cure for CHD
Drugs
By Pass Operations – Using a blood vessel from the chest, arm or leg to replace the diseased vessel.
Heart Transplanted

19. Prevention of CHD
Screening
Encouraging a healthy lifestyle

20. With reference to coronary heart bypass surgery, discuss the difficulties in achieving a balance between prevention and cure.