Topic 6.4: Gas Exchange Flashcards Preview

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Flashcards in Topic 6.4: Gas Exchange Deck (14)
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Exchange of gases between the lungs and the atmosphere (achieved by the physical act of breathing)


Ventilation and Cell Respiration

These gases are integral to the process of cell respiration
• Oxygen is an input, carbon dioxide is a by-product


Ventilation and Concentration Gradients

Ventilation maintains the concentration gradient necessary
for passive diffusion (O2 = into lungs, CO2 = out of lungs)


Ventilation Rates

Ventilation rates will change with exercise and can be
measured via spirometry (measures amount / rate of air)


Mechanisms of Breathing

Breathing utilises antagonistic sets of respiratory muscles to facilitate the passage of air (inhalation / exhalation)
• Muscles change lung volume to create negative pressure
• Negative pressure is equalised by air from atmosphere
• Air flows in / out according to the volume of the thorax



• Diaphragm muscles contract (diaphragm flattens)
• External intercostal muscles pull ribs up (outwards)
• This increases the volume of the thoracic cavity
• Pressure in lungs decreases below atmospheric pressure
• Air flows into the lungs in order to equalise the pressure



• Diaphragm muscles relax (diaphragm curves upwards)
• Internal intercostal muscles pull the ribs down (inwards)
• Abdominal muscles contract to push diaphragm upwards
• This decreases the volume of the thoracic cavity
• Pressure in lungs increases above atmospheric pressure
• Air flows out of the lungs to equalise the pressure



Pneumocytes (alveolar cells) line the alveoli and comprise
the majority of the inner surface of the lungs


Type I pneumocytes

• Involved in gas exchange between alveoli and capillaries
• Are extremely thin (minimises gas diffusion distances)


Type II pneumocytes

• Responsible for the secretion of pulmonary surfactant
• This creates a moist surface that reduces surface tension
(prevents sides of alveoli from adhering to each other)


Lung Cancer

Cancer is uncontrolled cell proliferation, leading to tumors
• Lungs possess a rich blood supply (for gas exchange),
increasing the chances of metastasis (spread of cancer)


Factors of Lung Cancer

• Intrinsic: Genetics, age, certain diseases / infections
• Extrinsic: Smoking, asbestos, radiation exposure



abnormal Enlargement of the alveoli
• These form air spaces and lower the overall surface area


Emphysema and Smoking

• Chemicals in the cigarettes damage the alveoli
• Phagocytes release elastase as part of immune response
• Elastase destroys the elastic fibres in the alveolar walls
• Huge air spaces (pulmonary bullae) develop in the lungs