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Human breathing mechanism


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About human breathing mechanism & gaseous exchange across respiratory surfaces

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Human breathing mechanism

  1. 1. • Internal intercostal muscle • External intercostal muscle • Rib cage • Diaphragm • Volume of thoracic cavity • Air pressure in alveoli • Air moves in @ out
  2. 2. Internal intercostal muscle relaxed External intercostal muscle contract Rib cage moves upwards & outwards Diaphragm contracts & flattens Volume of thorax cavity increase Pressure in alveoli decrease Air moves in
  3. 3. Internal intercostal muscle contract External intercostal muscle relaxed Rib cage moves downwards & inwards Diaphragm relaxes Volume of thorax cavity decrease Pressure in alveoli increase Air moves out
  4. 4. 1. Gaseous Exchange Across Surfaces of Alveolus and Blood Capillaries - The greater the gradient of concentration across respiratory surface, the greater the rate of diffusion - Diffusion of gas depends on the differences in partial pressure between two regions
  5. 5. 1. Gaseous Exchange Across Surfaces of Alveolus and Blood Capillaries • Partial pressure of 𝑂2 in alveoli is HIGHER than partial pressure of 𝑂2 in blood capillaries • Therefore, 𝑂2 diffuse across the surface of alveolus and blood capillaries into the blood
  6. 6. • Partial pressure of 𝐶𝑂2 is LOWER in the air of alveoli compared to blood capillaries • Therefore, 𝐶𝑂2 diffuse out of the blood capillaries into the alveoli.
  7. 7. • Gug summary
  8. 8. 2. Transport of respiratory gases in humans
  9. 9. OXYGEN • After gaseous exchange take place, 𝑂2 in blood is transported to body cells for cellular respiration • In blood, 𝑂2 combines loosely with the respiratory pigment called haemoglobin • 𝑂2 is carried in the form of oxyhaemoglobin to all parts of the body Haemoglobin + Oxygen Oxyhaemoglobin not stable !
  11. 11. CARBON DIOXIDE • 𝐶𝑂2 released by respiring cells can be transported in three ways: • Most of the bicarbonate ions are carried in the blood plasma to the lungs and diffuse from blood plasma to red blood cells & form carbonic acid again later on breaks down into 𝐶𝑂2
  12. 12. 3. Gaseous Exchange Between Blood and Body Cells • In tissue capillaries: partial pressure of oxygen in blood is higher • In cells: partial pressure of oxygen is lower (due to cellular respiration) • Hence, oxyhaemoglobin breaks down & release oxygen, which then diffuse through capillary walls into the cell
  13. 13. 4. Composition of Inhale and Exhale Air