Topic 6.4 Flashcards

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1
Q

Ventilation

A
  • Fresh air is pumped into the alveoli
  • Stale air is removed
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2
Q

What is the purpose of ventilation

A
  • Maintain the concnetration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries
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3
Q

Explain the role of concentration gradient in the procuess of gas exchange

A
  • Gases diffuse between alveoli and capillaries only if a concentration gradient exist
  • The air in the alveolus has a higher oxygen concentration
  • The air in blood has a higher carbon dioxide concentration
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4
Q

Type I pneumocytes

A
  • Extremely thin alveolar cells that are adapted to carry out gas exchange
  • Epithelium of alveolus
  • Thin, enable gas exchange
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5
Q

Type II pneumocytes

A
  • Rounded cells that occupy little space of alveolar surface area
  • Secrete a fluid which coats the inner surface of the alveoli
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6
Q

Annotate the following diagram of an alveolus

A

Refer to picture

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7
Q

Outline the purpose of the solution secreted by Type I penumocytes

A
  • This moisture allows oxygen in the alveolus to dissolve and diffuse into the capillaries
  • The fluid provides an area from which carbon dioxide can evaporate into the air and be exhaled
  • Contains a pulmonary surfactant
  • Reduces surface tension and prevents the water from causing the sides of the alveoli to adhere when the air is exhaled from the lungs (prevent collapse of the lung)
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8
Q

Annotate the following diagram of a lung

A

Refer to picture

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9
Q

Trachea

A
  • Rings of cartilage in its wall to keep it open even when air pressure inside is low or pressure in surrounding tissues is high
  • Divides to form two bronchi, leading to two lungs
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10
Q

Bronchioles

A
  • Tree-like structure of narrower airways that bronchi divide into
  • Smooth muscle fibres in their walls, allowing the width of these airways to vary
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11
Q

Where does gas exchange occur

A

Alveoli

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12
Q

Describe muscle contraction during inspiration

A
  • Diaphragm moves downwards and flattens
  • Ribcage moves upwards and outwards
  • Cause the pressure inside the thorax to drop below atmospheric pressure
  • Air is drawn into the lungs from the atmosphere
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13
Q

Describe muscle contraction during expiration

A
  • Diaphragm moves upwards and become more domed
  • Ribcage moves downwards and inwards
  • Cause the pressue inside the thorax to increase
  • Air is pushed out
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14
Q

Describe the antagonistic muscle pairs in respiration

A
  • When diaphragm contracts, abdomen wall muscles relaxes
  • When external intercostal muscles contract, internal intercostal muscles relax
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15
Q

Outline the five causes of lung cancer

A
  • Tobacco smoke contains mutagenic chemicals and increase the incidence of lung cancer
  • Passive smoking (non-smokers inhale tobacco smoke exhaled by smokers)
  • Air pollution (diesel exhaust fumes, nitrogen oxides, smoke from burning coal, wood, or other organic matter)
  • Radon gas (radioactive gas that leaks out of certain rocks and accumulates in badly ventilated buildings)
  • Asbestos, silica and some other solids if dust or other particles of them are inhaled (construction sites or quarries, mines or factories)
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16
Q

Outline the consequences of lung cancer

A
  • Difficulties with breathing
  • Persistent coughing
  • Coughing up blood
  • Chest pain
  • Loss of appetite
  • Weight loss
  • General fatigue
17
Q

Emphysema

A
  • Thin-walled alveoli is replaced by larger air sacs with much thicker walls
  • Total suface area for gas exchange is reduced
  • Distance over which diffusion of gases occurs is increased
  • Gas exchange is less effective
18
Q

Outline the function of phagocytes inside alveoli

A
  • Prevent lung infections by engulfing bacteria
  • Produce elastase, a protein-digesting enzyme, to kill them inside the vesicles formed by endocytosis
19
Q

Alpha 1-antitrypsin (A1 AT)

A
  • Enzyme inhibitor that prevents elastase and other proteases from digesting lung tissue
  • In smokers, the number of phagocytes in the lungs increase and they produce more elastase
20
Q

Outline the consequences of emphysema

A
  • Low oxygen saturation in the blood
  • Higher than normal carbon dioxide concentration
  • Patient lacks energy, shortness of breath, laboured ventilation
21
Q

Outline the possible causes of emphysema

A
  • While the molecular mechanisms involved are not fully understood, there is evidence that cancer is a cause
  • Cigarette smoke contains chemical irritants that damage the alveolar walls
  • The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
  • This elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall
  • Elastase activity can be usually be blocked by an enzyme inhibitor (α-1-antitrypsin), but not when elastase concentrations are increased
  • A small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation