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Gas Exchange

Gas Exchange. Week 4. Daltons Law. The partial pressures of the 4 gases add up to 760mm Hg. Dalton’s Law; in a mixture if gases, the total pressure equals the sum of the partial pressures exerted by each gas. Important Point.

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Gas Exchange

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  1. Gas Exchange Week 4

  2. Daltons Law

  3. The partial pressures of the 4 gases add up to 760mm Hg. Dalton’s Law; in a mixture if gases, the total pressure equals the sum of the partial pressures exerted by each gas.

  4. Important Point • Gases in our bodies are dissolved in fluids, such as blood plasma. • According to Henry’s law, • gases dissolve in liquids in proportion to their partial pressures, depending also on their solubilities in the specific fluids and on the temperature.

  5. The Site of Gas Exchange • External Respiration • CO2 diffuses from pulmonary capillaries into alveoli • O2 Diffuses from alveoli into pulmonary capillaries • Internal respiration • O2 diffuses from systemic capillaries into cells • CO2 diffuses from cells into systemic capillaries

  6. Factors Influencing External Respiration • Efficient external respiration depends on 3 main factors • Surface area and structure of the respiratory membrane • Partial Pressure gradients • Matching alveolar airflow to pulmonary capillary blood flow.

  7. Important Point • Partial pressure gradients affect gas exchange between the alveoli and pulmonary capillaries.

  8. External respiration: Partial Pressures • The Partial pressures of gases in the alveoli differ from those in the atmosphere. • Humidification of inhaled air • Gas exchange between alveoli and pulmonary capillaries • Mixing of new and old air

  9. Oxygen Loading • Oxygen diffuses along its partial pressure gradient, from the alveolus into the blood, until equilibrium is reached • Equilibrium is reached within the first third of the capillary.

  10. OxygenLoading

  11. Carbon Dioxide Uploading • Carbon dioxide diffuses along its partial pressure gradient, from the blood into the alveolus, until equilibrium is reached • Equilibrium is reached within the first 4 4/10’s of the capillary

  12. This Occurs Simultaneously • Carbon dioxide is very soluble in blood, allowing many molecules to diffuse along this small pressure gradient. • Oxygen is less soluble, requiring a larger concentration gradient.

  13. Other Factors Affecting External Respiration • Matching alveolar airflow to pulmonary capillary blood flow. • Watch the following clip. • This is Know as the Ventilation-Perfusion Coupling

  14. Internal Respiration • Internal Respiration • O2 diffuses from systemic capillaries into cells • CO2 diffuses from cells into systemic capillaries.

  15. Internal Respiration Depends on: • Available surface area, which varies in different tissues. • Partial Pressure gradients • Rate of blood flow varies (e.g. metabolic rate of tissue)

  16. Internal Respiration CO2 and O2 Exchange

  17. Summary

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