gas exchange and transport Flashcards
(35 cards)
Once air enters lungs how does O2 enter bloodstream & CO2 leave?
Gas exchange at the respiratory membrane
describe the respiratory membrane layers
= 6 thin layers between alveolus & capillary
name the 6 diff layers of the respiratory membrane
- fluid and surfactant layer
- alveolar epithelium
- epithelial basement membrane
- interstitial space
- capillary basement membrane
- capillary endothelium
Respiratory Membrane is efficient because of:
- Substantial differences in partial pressures across respiratory membrane
- which leads to fast rate of gas diffusion - . Small distances involved in gas exchange
- Gases are lipid soluble
- Total surface area large
what is Partial pressure (Px)
pressure exerted by each gasx type in a mixture
explain daltons law
Px = % gasx times total pressure
So, gas moves from high Px to low Px
explain the movement of gasses due to Px
Usually PO2 alveolar > blood
Whereas PCO2 blood > alveolar
this indicates that gas is moving from one tissue to another.
Why feel lightheaded at high altitude?
Less O2 in alveoli, so ….
Slower diffusion into blood.
explain the effect of high altitude (in terms of a water bottle filled w air)
LHS bottle filled at high altitude (so low pressure of air inside bottle)
Taken to sea level, bottle flattens as higher pressure outside bottle than inside (RHS).
explain the process of internal and external respiration
external = pulmonary gas exchange
internal = systemic gas exchange
external:
on inhale oxygen is taken into alveoli then along pulmonary capillaries to left atrium. then….
internal:
….. oxygen goes along systemic capillaries to systemic tissue cells. carbon dioxide then exits the systemic tissue cells and transports along systemic capillaries to the right atrium and then to the lung and out via the alveoli into the atmosphere
explain how Respiratory Membrane is efficient because of: Small distances involved in gas exchange
Thickness of Respiratory Membrane?
= 0.5mm
Decreased efficiency
if fluid builds up, as in
tuberculosis or
pneumonia
(RBC diameter = 6-8um)
explain how Respiratory Membrane is efficient because of: Gases being lipid soluble
O2 & CO2 readily diffuse through surfactant layer & alveolar & endothelial cell membrane
explain how Respiratory Membrane is efficient because of: Total surface area being large
Respiratory membrane s.a. ~70m2
= half singles tennis court.
How are O2 & CO2 transported in the blood?
O2 & CO2 have limited solubilities in blood plasma
Problem solved by red blood cells (RBC) as :
- bind O2
- use CO2 to manufacture soluble compounds
(these are both temporary effects and completely reversible)
explain the gas diffusion into blood (such as why it happens)
Because these reactions in RBC remove dissolved gas from the plasma, gas will continue to diffuse into blood but never reach equilbrium
explain oxygen transport
O2 bound to iron ions in centre of each haem unit in a Hb molecule
4 haem units per Hb so 4x O2 per Hb molecule
~280 million Hb in each RBC
Each RBC potentially carry >billion O2 molecules
in tissue spaces, oxygen diffuses what direction from Hb and what happens to it
away from Hb and enters tissues
name 4 factors that influence the degree to which oxygen binds to Hb
P02
- oxygen-haemoglobin dissociation/saturation curve describes %Hb saturated at any PO2
blood PH
- Bohr effect
temperature
ongoing metabolic activity within RBC
explain how Po2 influence the degree to which O2 binds to Hb
Curve (cf. straight line) as once bound, easier to bind 2nd molecule
- Easier to bind 2nd molecule of O2 due to shape change after 1st O2 bound. If CO is just 0.1% of air, enough Hb affected to die if not receive medical assistance; treat with pure O2 or transfuse with compatible RBC.
Carbon monoxide poisoning occurs as CO binds to Hb 200x stronger than O2
Lethal % CO level in air = 0.1%
explain the O2-Haemoglobin Dissociation curve
If curve shifts to right, O2 released to tissues
in the dissociation curve O2 released to tissues with…
Increasing temperature
Decreasing pH (more acidic)
when do tight binding structure occur and what do they do
DPG = (di/biphosphoglycerate)
When 2,3-DPG binds to the Hb, the O2 is released
what does a left shift curve mean and why
increased uptake of O2 in lungs
As Hb has increased ability to pick up O2
explain Blood pH, Bohr effect
factors at influencing the degree to which oxygen binds to Hb
H+ binds to protein part of Hb
which affects shape of Hb
which affects amount of O2 carried
(Active tissue generates acid therefore decrease in pH therefore O2 released to tissues, where needed. Bohr effect (named after Danish physiologist Christian Bohr), is that Hb 2 binding affinity inversely proportional to acidity & CO2 concentration)
