6.4 Gas Exchange

Question 1

Gas exchange

Answer 1

is the process of swapping carbon dioxide for oxygen
this happens in the alveoli by the process of diffusion down concentration gradients between blood and air

Question 2

Ventilation

Answer 2

the exchange of air between the atmosphere and the lungs

Question 3

Where does air travel?

Answer 3

enters through the nose or mouth and passes through the pharynx to the trachea.
It then trabels down the trachea until it divdes into two bronchi which connect to the lungs
Inside the lungs the bronchi divides into bronchioles (small airways) that increase the surface area
Alveoli are at the end of these bronchioles

Question 4

Alveoli

Answer 4

they provide a huge surface area for gas exchange
they consist of a single layer of thin cells so the gases only have to diffuse a short distance
they are covered by a dense network of blood capillaries with low oxygen and high carbon dioxide concentrations
hence allowing diffusion
they secrete a fluid that keeps the inner surface of the alveolus moist allowing gases to dissolve

Question 5

Inspiration

Answer 5

The muscles responsible for inspiration are the diaphragm and external intercostals (plus some accessory muscles)

Diaphragm muscles contract, causing the diaphragm to flatten and increase the volume of the thoracic cavity
External intercostals contract, pulling ribs upwards and outwards (expanding chest)
Additional muscle groups may help pull the ribs up and out (e.g. sternocleidomastoid and pectoralis minor)

Question 6

Expiration

Answer 6

The muscles responsible for expiration are the abdominal muscles and internal intercostals (plus some accessory muscles)

Diaphragm muscles relax, causing the diaphragm to curve upwards and reduce the volume of the thoracic cavity
Internal intercostal muscles contract, pulling ribs inwards and downwards (reducing breadth of chest)
Abdominal muscles contract and push the diaphragm upwards during forced exhalation
Additional muscle groups may help pull the ribs downwards (e.g. quadratas lumborum)

Question 7

Avelolar cell types

Answer 7

Type I pneumocytes - extremely thin avelolar cells that are adapted to carry out gas exchange
Type II pneumocytes - secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the alveolus from sticking to one another by reducing surface tension
Alveolar macrophages - (dust cells) are wandering macrophages that destroy bacteria and remove particulate matter

Question 8

Causes of lung cancer

Answer 8

Radiation
Aging
Pollution
Environment
Diseases
Genetics
Occupation
Asbestos
Tobacco
Smoke

Question 9

Consequences of lung cancer

Answer 9

Shortness of breath
Coughing up blood
Pain
Fluid in chest
cancer that spreads to other parts of body (metastasis)
Shortened lifespan

Question 9

Emphysema

Answer 9

Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls

The loss of elasticity results in the abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange
The degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae)

The major cause of emphysema is smoking, as the chemical irritants in cigarette smoke damage the alveolar walls

Common symptoms of emphysema include shortness of breath, phlegm production, expansion of the ribcage, cyanosis and an increased susceptibility to chest infections