Lecture 18 Flashcards
External respiration
Diffusion of o2 from alveoli into blood in pulmonary capillaries + diffusion of co2 in opposite direction
In pulmonary gas exchange (external respiration), each gas diffuses
Independently
Deoxygenated blood from right side goes in lungs to get
oxygenated and go back to heart by left side
P of a specific gas in a mixture is called
Partial P
Po2 (partial pressure of o2) and Pco2 in atm
Po2: 159 mmHg
Pco2: 0.3mmHg
The greater the diff in partial pressure
The faster the rate of diffusion
External respiration occurs in
Lungs
Po2 and pco2 in alveolar air
Po2: 105 mmHg
Pco2: 40 mmHg
Diffusion of o2 in external respiration
From alveolar air (105 mmHg) to blood in pulmonary capillaries (40 mmHg)
Diffusion of co2 in external respiration
From deoxygenated blood (45 mmHg) to alveoli (40mmHg)
Diffusion of o2 in blood occurs until pulmonary capillary blood Po2 is
105 mmHg (like alveolar air)
Blood at 105 mmHg (after diffusion to equalize) mixes with blood supply to lung so that po2 in pulmonary veins returning to left side of heart =
100 mmHg
Pco2 45 mmHg of deox blood diffuses into alveoli until 40 mmHg in both so that oxy blood going back to left side of heart has pco2 of
40mmHg
During exercise, is the po2 in pulmonary capillaries higher or lower than 40 mmHg
Lower due to increase use of o2
3 factors influence external respiration
- Partial P gradient and gas solubilities
- Thickness and surface area of respiratory membranes
- Ventilation-perfusion coupling
Co2 is ___x more soluble than oxygen
20x
The greater the surface area, the
More efficient gas exchange
Respiratory membrane is very tuin (0,5 um) so it allows
Rapid diffusion of gases
Thickness of respiratory membrane increases with
Edema, pneumonia, heart failure (slows rate if gas exchange)
For optimal gas exchange, rate of ventilation (gas reaching alveoli) must
Match rate of perfusion (blood flow in pulmonary capillaries)
Ventilation-perfusion coupling is the process that
Coordinates respiratory and cardiovascular systems to deliver o2 to body tissues
Body responds to changes in ventilation by
Adjusting blood flow (airflow increases, blood flow too)