The Atmosphere

Question 1

What are the percentages of the main gases in the atmosphere?

Answer 1

• Nitrogen = 78%
• Oxygen = 21%
• Other = 1% (Argon, Ozone, Xenon, CO2, Helium, Methane, Neon, H2O, Hydrogen)

Question 2

What is the variation of pressure as altitude increases?

Answer 2

• Pressure decreases with an increase in altitude
• 18,000ft, pressure = 1/2 of sea level pressure
• 33,500ft, pressure = 1/4 of sea level pressure
• 100,000ft, pressure = approx 100th of sea level pressure

Question 3

What is the partial pressure of oxygen which changes as altitude increases?

Answer 3

• Multiply the pressure of the atmosphere by the amount of oxygen.
  E.g. the pressure of the atmosphere at sea level is 760mmHg, there the partial pressure of oxygen at sea level = 760 x 0.21
• At 18,000ft the partial pressure of oxygen is 79.5mmHg

Question 4

Explain the physiology of the respiratory system.

Answer 4

• Air enters through nose and mouth, travels to the lungs via the trachea, the trachea divides into two bronchi, each bronchi then divides many times into bronchioles, each of which ends with alveoli.
• Alveoli provides the surface where the oxygen diffuses into the blood and carbon dioxide is removed, then oxygen is taken up by haemoglobin in the red blood cells and transported throughout the body.

Question 5

Explain the physiology of the circulatory system.

Answer 5

• Oxygen rich blood travels from the lungs through the pulmonary vein to the left atrium.
• Through the heart from the left atrium to the left ventricle.
• Then through the aorta to the arteries and arterioles which distribute oxygenated blood to all part of the body via the tissue capillaries.
• Oxygen poor blood travels from the capillaries, through the venues and then veins to the right atrium
  -Then through the heart, from the gift atrium to the right ventricle
• Back to the lungs via the pulmonary artery, where the blood is removed-oxygenated.

Question 6

What is the role of the lungs in oxygen and carbon dioxide transfer?

Answer 6

Breathing:
Air into lungs = inhalation, inspiration - breathe out CO2

Diaphragm contracts (flattens) = more volume in chest cavity = less pressure

Diaphragm relaxes (dome shape) = less volume in chest cavity = high pressure