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Biology A-Level > Gas Exchange and Smoking (Chapter 9) > Flashcards

Gas Exchange and Smoking (Chapter 9) Flashcards

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1
Q

What are the lungs surrounded by and what do these do?

A

Pleural membranes - these enclose an airtight space which contains a small quantity of fluid to allow friction-free movement as the lungs are ventilated by the movement of the diaphragm and ribs

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2
Q

Describe the order of the breathing system

A 
Trachea
Two bronchi (bronchus)
Bronchioles
Terminal bronchioles
Alveoli
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3
Q

What do trachea and bronchi contain (but not bronchioles)?

A

Cartilage

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4
Q

Describe the cartilage in the trachea

A

A regular arrangement of C-shaped rings

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5
Q

Describe the cartilage in the bronchi

A

Irregular blocks

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6
Q

What is the function of cartilage in the trachea and bronchi?

A
  • To keep these airways open and air resistance low

- Prevents them from collapsing and bursting as the air pressure changes during breathing

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7
Q

What are bronchioles surrounded by?

A

Smooth muscle

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8
Q

What is the function of smooth muscle in the bronchioles?

A

It can contract or relax to adjust the diameter of these very small airways

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9
Q

What happens in the bronchioles during exercise?

A

The smooth muscle relaxes to allow a greater flow of air to the alveoli. (The absence of cartilage makes these adjustments possible)

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10
Q

What is desiccation?

A

Drying out

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11
Q

How are surfaces inside the lungs protected from desiccation?

A

As air flows through the nose and trachea, it is warmed to body temp and moistened by evaporation from the lining

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12
Q

How do goblet cells and ciliated epithelial cells protect the lining of the trachea (and bronchi)?

A
  • Goblet cells secrete mucus which traps dust and bacteria
  • The mucus is then removed from the trachea by ciliated epithelial cells which sweep the mucus upwards towards the throat where it is swallowed
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13
Q

Where are goblet cells found?

A

In the trachea and bronchi (and nasal airways)

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14
Q

What is mucus?

A

A slimy solution which is composed of glycoproteins with many carbohydrate chains that make them sticky and able to trap particles

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15
Q

Where is mucus produced/secreted?

A
  • Mucin droplets (containing mucus) are secreted by goblet cells
  • Mucous glands beneath the endothelium
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16
Q

How can chemical pollutants (e.g. NO2 and SO2) irritate the lining of the airways?

A

They dissolve in mucus to form an acidic solution

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17
Q

Where are the ciliated cells?

A

Between the goblet cells

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18
Q

What do ciliated cells do?

A
  • The continual beating of their cilia carries the carpet of mucus upwards towards the throat (larynx)
  • When mucus reaches the top of the trachea it is usually swallowed so that pathogens are destroyed by the acid in the stomach
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19
Q

What do alveolar walls contain?

A

Elastic fibres

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20
Q

What is the function of elastic fibres in alveolar walls?

A
  • They stretch during inspiration and recoil during expiration to help force out air
  • This elasticity allows alveoli to expand according to volume of air breathed in
  • They prevent bursting of the alveoli
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21
Q

What happens to the alveoli during exercise

A

During exercise, the alveoli are fully expanded so the surface area available for diffusion increases, and the air is expelled efficiently when the elastic fibres recoil

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22
Q

How are alveoli adapted so that the diffusion pathway for O2 and CO2 is very short?

A

They have extremely thin walls - each consisting of a single layer of squamous epithelial cells no more than 0.5μm thick

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23
Q

What are the two ways that a steep concentration gradient is maintained so that gas exchange can take place rapidly?

A

Breathing

Movement of the blood

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24
Q

How does breathing and constant movement of blood maintain a steep concentration gradient?

A
  • Breathing brings fresh supplies of oxygen to the lungs with a relatively high O2 conc and low CO2 conc, increasing the O2 conc in the alveoli
  • Blood is brought to the lungs with a lower O2 conc and higher CO2 conc than the air in the alveoli
  • Oxygen therefore diffuses down its concentration gradient from the air in the alveoli to the blood and carbon dioxide in the opposite direction
  • The blood is constantly flowing through and out of the lungs, so, as the oxygenated blood leaves, more deoxygenated blood enters to maintain the conc gradient with each new breath
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25
Q

What are the two types of smoke that tobacco smoke is made up of?

A

‘mainstream’ and ‘sidestream’ smoke

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26
Q

What is passive smoking?

A

Breathing in someone else’s smoke

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27
Q

What are the main dangerous components in cigarette smoke and what systems do they damage in general?

A

Tar (containing carcinogens) - gas exchange system

Carbon monoxide and nicotine - cardiovascular system

28
Q

What is tar?

A

A mixture of compounds that settles on the lining of the airways in the lungs and stimulates a series of changes that may lead to obstructive lung diseases and lung cancer

29
Q

What are carcinogens?

A

Cancer-causing compounds which cause mutations in the genes that control cell division

30
Q

What are lung diseases caused by?

A

Smoking, air pollution and allergic reactions

31
Q

What is the basic way in which lung diseases are caused?

A
  • Very small particles can reach the alveoli and settle out easily because the air flow in the depths of the lungs is very slow
  • Such deposits make the lungs susceptible to airborne infections such as influenza, and in some people, can cause an allergic reaction leading to asthma
32
Q

What does COPD stand for?

A

Chronic obstructive pulmonary diseases

33
Q

What does chronic mean?

A

Long term

34
Q

Give examples of COPD

A

Asthma, chronic bronchitis and emphysema

35
Q

What is the effect of tar in cigarette smoke on the lungs?

A
  • It stimulates goblet cells and mucus glands to enlarge and secrete more mucus
  • It also inhibits the cleaning action of the ciliated epithelium that lines the airways by destroying many cilia and weakening the sweeping action of those that remain
36
Q

What is the effect of the excess mucus cause by tar on the airways?

A

1) Mucus accumulates in the bronchioles, and the smallest of these may become obstructed
2) As mucus is not moved, or at best only moved slowly, dirt, bacteria and viruses collect and block the bronchioles
3) This stimulates ‘smoker’s cough’ which is an attempt to move the mucus up the airways
4) With time, the damaged epithelia are replaced by scar tissue and the smooth muscle surrounding the bronchioles and bronchi becomes thicker
5) This thickening of the airways causes them to narrow and makes it difficult to breathe

37
Q

What else can develop as a result of excess mucus?

A
  • Infections, such as pneumonia easily develop in the accumulated mucus
  • When there is an infection in the lungs, the linings become inflamed ad this further narrows the airways
38
Q

What is chronic bronchitis?

A

A symptom of the damage and obstruction of airways as a result of excess mucus from tar

39
Q

What do sufferers of chronic bronchitis have?

A

A severe cough, producing large quantities of phlegm

40
Q

What causes emphysema?

A

1) The inflammation of the constantly infected lungs causes phagocytes to leave the blood and line the airways
2) To reach the lining of the lungs from the capillaries, phagocytes release the protein-digesting enzyme elastase
3) This enzyme destroys elastin in the walls of the alveoli, making a pathway for the phagocytes to reach the surface and remove bacteria

41
Q

What is elastin responsible for?

A

The recoil of the alveoli when we breathe out

42
Q

What happens as a result of the destruction of elastin?

A

1) With much smaller quantities of elastin in the alveolar walls, the alveoli do not stretch and recoil when breathing in and out
2) As a result, the bronchioles collapse during expiration, trapping air in the alveoli, which often burst
3) Large spaces appear where the alveoli have burst, and this reduces the SA for gas exchange
4) The number of capillaries also decreases, so less oxygen is absorbed into the blood
4) The loss of elastin makes it difficult to move air out of the lungs so the air is remains in the lungs and is not refreshed during ventilation
5) Therefore, many people with emphysema do not oxygenate their blood very well and have a rapid breathing rate

43
Q

What happens as emphysema progresses?

A

1) The blood vessels in the lungs become more resistant to the flow of blood
2) To compensate for this increased resistance, the blood pressure in the pulmonary artery increases and over time, the right side of the heart enlarges

44
Q

What do people with severe emphysema often require?

A

A continuous supply of oxygen through a face mask

45
Q

What do diseases often occur together?

A

Chronic bronchitis and emphysema

46
Q

How is lung cancer caused by smoking?

A

The carcinogens in tar react, directly or via breakdown products, with DNA in epithelial cells to produce mutations, which are the first in a series of changes that lead the the development of a mass of cells (tumour)

47
Q

What happens as lung cancer develops?

A

It spreads through the bronchial epithelium and enters the lymphatic tissues in the lung
- cells may break away and spread to other organs, so that secondary tumours become established

48
Q

How long does lung cancer take to develop?

A

20-30 years

49
Q

What is the most common symptom of lung cancer?

A

Coughing up blood, as a result of tissue damage

Also chest pain and difficulty breathing

50
Q

How can tumours in the lungs be located?

A

1) Breathoscopy
2) Chest X-ray
3) CT scan

51
Q

What is the treatment for lung cancer?

A

Surgery, radio/chemo therapy or anti-cancer drugs

52
Q

What are the two components of tobacco smoke that cause short-term effects on the cardiovascular system?

A

Nicotine and carbon monoxide (CO)

53
Q

What is nicotine?

A

The drug in tobacco that is absorbed very readily by the blood and travels to the brain within a few seconds

54
Q

What does nicotine stimulate the nervous system to do?

A

Reduce the diameter of the arterioles and release adrenaline from the adrenal glands

55
Q

What is the effect of nicotine reducing the diameter of the arterioles and releasing adrenaline?

A

Heart rate and blood pressure increase and there is a decrease in blood supply to the extremities of the body e.g. hands and feet, reducing their supply of oxygen
- nicotine also increases the risk of blood clotting

56
Q

How is nicotine a highly addictive drug?

A

It influences rewards centres in the brain by stimulating nerve endings in the brain to release dopamine (a transmitter substance), which is associated with reinforcing pleasurable experiences

57
Q

What is the effect of nicotine being highly addictive?

A

It is very difficult to stop smoking

58
Q

What does carbon monoxide do in the body and what is the effect?

A

1) It diffuses across the walls of the alveoli into the blood in the lungs
2) Here it diffuses into RBCs where it combines with Hb to form the stable compound carboxyhaemoglobin
3) This means that Hb does not become fully oxygenated and the quantity of oxygen transported in the blood may be 5-10% less than normal
4) Therefore, less oxygen is supplied to the heart muscle, putting a strain on it, esp when the heart rate increases during exercise

59
Q

How significant are the effects of CO?

A

They are reversible in the short-term but the effect on long-term smokers is more significant

60
Q

What other effects does carbon monoxide have on the arteries?

A

1) CO may also damage the lining of the arteries
2) This may lead to the build up of fatty tissue and the reduction of blood flow
3) Coronary heart disease and stroke may be the result

61
Q

What are cardiovascular diseases?

A

Multifactorial diseases, meaning that many factors contribute to their development (incl. smoking)

62
Q

What do macrophages do in the airways?

A

They patrol the surfaces of the airways scavenging small particles such as bacteria and fine dust particles

63
Q

What parts of the lungs have cartilage?

A

The trachea and bronchi

64
Q

What parts of the lungs have goblet cells?

A

The trachea and bronchi

65
Q

What parts of the lungs have smooth muscle?

A

The trachea, bronchi and terminal bronchiole

66
Q

What parts of the lungs have cilia?

A

The trachea, bronchi, terminal bronchiole and a few in the respiratory bronchiole

Biology A-Level (44 decks)

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