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 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.

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

Factors Influencing External Respiration Efficient external respiration depends on 3 main factors 1)Surface area and structure of the respiratory membrane 2)Partial Pressure gradients 3)Matching alveolar airflow to pulmonary capillary blood flow.

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

External respiration: Partial Pressures The Partial pressures of gases in the alveoli differ from those in the atmosphere. 1)Humidification of inhaled air 2)Gas exchange between alveoli and pulmonary capillaries 3)Mixing of new and old air

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.

Oxygen Loading

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

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.

Other Factors Affecting External Respiration 1)Matching alveolar airflow to pulmonary capillary blood flow. 2)Watch the following clip. 3)This is Know as the Ventilation-Perfusion Coupling

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

Internal Respiration Depends on: 1)Available surface area, which varies in different tissues. 2)Partial Pressure gradients 3)Rate of blood flow varies (e.g. metabolic rate of tissue)

Internal Respiration CO2 and O2 Exchange

Summary