Read the summary and the most important questions on CASE 5: ''Live high, train low''

• 1 Gas exchange in the alveoli

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• When a breath is taken during inhalation, the concentration of the incoming oxygen is higher in the alveolus than in the erythrocytes, resulting in...

  Oxygen leaving the alveolus and entering the erythrocyte

• During exhalation, the concentration of CO2 is lower in the alveolus than in the erythrocytes, resulting in...

  CO2 leaving the erythrocyte and entering the alveolus 

• Reaction of hemoglobin and O2

  Hb + O2 <--> HbO2
  The central iron atom of each heme-group can bind reversibly with an oxygen molecule, iron-oxygen bond is weak that can easily be broken.
  1 hemoglobin molecule can bind 4 O2 molecules.
  In pulmonary capillaries, oxygen from alveoli first dissolves in plasma and then diffuses into red blood cells.

• Law of mass action

  As the concentration of free O2 increases, more oxygen binds to hemoglobin and the equation shifts to the right, producing more HbO2.

• 1.1.1 Type I pneumocytes

• What is the function of the thin walls of the squamous (type I) alveolar cells, also known as type I pneumocytes, which occur in 95% of the alveoli?

  The walls allow rapid gas exchange (CO2 and air)

• 1.1.2 Type II pneumocytes

• What are the two functions of the type II pneumocytes that occur at 5% of the alveoli?

  1. Secretion of pulmonary surfactant
     
  2. Repair alveolar epithelium when squamous is damaged

• 1.1.2.1 Pulmonary surfactant

• Surfactant is composed of phospolipids and proteins, what is it function?

  It coats the alveoli, preventing pressure build-up during exparation

• What would happen if surfactant was not present on alveoli?

  The walls of deflating alveoli would cling together, making it hard to re-inflate them

• 2 Dissociation curve

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• What does the oxygen dissociation curve (pO2) plot?

  %saturation against the partial pressure of oxygen

• Which 4 factors affect the % saturation of Hb, and so, the dissociation curve affected by?

  • pCO2
    
  • pH
  • Temperature
  • 2,3-DPG