Respiratory System Lecture 4 Flashcards
What pressure drives gas exchange?
Respiration is driven by pressure gradients of individual gases, not atmospheric pressure
What is Dalton’s Law?
- Total pressure exerted by a mixture of gases is the sum of pressures exerted independently by each gas in a mixture (partial pressure).
- Overall pressure is sum total of all individual gas partial pressures in a mixture
Determining the partial pressure of a gas:
How is OXYGEN exchanged between ALVEOLI and LUNG CAPILLARIES? (4)
- In the alveoli, the partial pressure of oxygen (PO2) is 105 mmHg.
- In the arterial blood arriving at the lungs, the PO2 is 40 mmHg.
- This creates a pressure gradient from the alveoli to the lung capillaries, favouring the movement of oxygen from the alveoli into the bloodstream.
- As a result, oxygen moves from the alveoli (105 mmHg) into the lung capillaries and oxygenates the blood, raising its PO2 to approximately 100 mmHg. The oxygenated blood then travels to various tissue cells for cellular respiration.
How is CARBON DIOXIDE exchanged between ALVEOLI and LUNG CAPILLARIES? (4)
- In the alveoli, the partial pressure of carbon dioxide (PCO2) is 40 mmHg.
- In the arterial blood arriving at the lungs, the PCO2 is 46 mmHg.
- This creates a pressure gradient from the lung capillaries to the alveoli, favouring the movement of carbon dioxide from the bloodstream into the alveoli.
- As a result, carbon dioxide moves from the lung capillaries (46 mmHg) into the alveoli and is then expired when you breathe out.
What partial pressures of gasses does the Pulmonary circulation take back to the heart to be pumped out into systemic circulation?
Pulmonary circulation transports oxygenated blood with a partial pressure of approximately 100 mmHg O2 and 40 mmHg CO2 from the lungs back to the heart,
which is then pumped into the systemic circulation to deliver oxygen to body tissues. This oxygen-rich blood sustains cellular respiration and supports the body’s metabolic functions.
How is movement across the alveolar-capillary membrane regulated? (4)
- Partial pressure gradient of gas.
- Surface area for diffusion.
- Thickness of membrane gas is diffusing through.
- Diffusion coefficient of gas (amount that can cross an area in 1 second)
How is OXYGEN exchanged between TISSUE CAPILLARIES and INTERSTITAL FLUID/TISSUE CELLS? (3)
- O2 moves from arterial blood with a high partial pressure (100 mmHg) to tissue cells with a lower partial pressure (< 40 mmHg).
- This transfer occurs through a pressure gradient from tissue capillaries to tissue cells.
- As a result, blood entering tissue capillaries is oxygenated (100 mmHg) and leaves deoxygenated (40 mmHg), supplying oxygen to the tissue cells for their metabolic needs.
How is CARBON DIOXIDE exchanged between TISSUE CAPILLARIES and INTERSTITAL FLUID/TISSUE CELLS? (4)
- CO2 moves from tissue cells with a high partial pressure (> 46 mmHg) to arterial blood with a lower partial pressure (40 mmHg).
- This exchange takes place through a pressure gradient from tissue cells to tissue capillaries.
- Consequently, blood entering tissue capillaries has a lower partial pressure of carbon dioxide (40 mmHg) and leaves with a higher partial pressure (46 mmHg), with the intent of transporting the carbon dioxide to the lungs for eventual expiration.
What are the partial pressures of O2 and CO2 does the Systemic circulation back to the heart to be pumped out into pulmonary circulation?
deoxygenated blood
(O2 40 mmHg / CO2 46 mmHg)
back to the heart to be pumped out into pulmonary circulation.
How is the movement across tissue capillary – interstitial fluid – tissue cell membrane regulated? (4)
- Partial pressure gradient of gas.
- Surface area for diffusion.
- Thickness of membrane gas is diffusing through.
- Diffusion coefficient of gas (amount that can cross an area in 1 second).
(Same as for external respiration just in a different location)
Henry’s Law:
At constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above a liquid
Problems and Solutions to Henry’s Law?
Problem:
Inefficient gas exchange because there isn’t enough dissolved O2 and CO2 in the blood to meet tissue metabolic needs, only dissolved gasses can participate in gas exchange
Solution:
Employ gas transporters to bind and effectively transport gases to meet tissue metabolic needs, allowing gases to temporarily bind for transport and then return to a dissolved state for gas exchange.
How can we Manipulate affinity (tightness of binding) to suit desired needs in response to the problems created by daltons law?
Lower affinity
- more likely to let go of the transporter (unloading).
Higher affinity
- more likely to hold on to the transporter (loading)
What happens to Oxygen once it enters the bloodstream? (5)
- 1.5% oxygen dissolved in plasma.
- 98.5% oxygen binds hemoglobin (Hb) for transport as oxyhemoglobin (HbO2) inside RBC.
- Each Hb can bind 0 – 4 oxygen molecules.
- At 100% = all sites occupied with an oxygen; fully saturated
- Lower percentage = not all sites occupied with an oxygen; partially saturated
Hb saturation w/ different O2 bound
Summary
