Gas Transport Flashcards
what do respiratory and circulatory systems function together to transport?
CO2 from tissues to lungs and O2 from lungs to tissues
what are the anatomical and physiological properties of the respiratory and circulatory systems which facilitate gas diffusion?
large surface area for gas exchange, large partial pressure gradients, gases with advantageous diffusion properties, specialised mechanisms for transporting O2 and CO2 between lungs and tissues
what is partial pressure?
fraction of gas in gas mixture x barometric pressure
what are the two forms that oxygen is transported in?
dissolved and bound to haemoglobin
how is dissolved O2 in the blood measured?
in an arterial blood sample
what is the amount of O2 dissolved in the blood proportional to?
the partial pressure
why is transport of O2 in dissolved form not adequate?
because during exercise the CO is 30L/min but the arterial blood contains 3ml O3/litre of blood so that would only be 90ml/min of O2 to tissues BUT tissue requirements may need 3000ml O2/min
what is haemoglobin?
major transport molecule for O2 found in red blood cells
what is the functional unit of haemoglobin?
4 haem groups joined to globin protein
what is the site of O2 binding?
iron in the reduced ferrous form (Fe+++)
what does the oxyhaemoglobin dissociation curve illustrate?
the relationship between PO2 in blood and the number of O2 molecules bound to Hb
what does the flat portion of the oxyhaemoglobin curve represent?
drop in PO2 from 100 to 60mmHg has minimal effect on Hb saturation
what does the steep portion of the oxyhaemoglobin curve represent?
large amount of O2 is released from Hb with only small change in PO2, facilitating release into tissues
how many O2 atoms can a Hb molecule bind to?
4
what is O2 saturation?
the amount of O2 bound to Hb relative to maximal amount that can bind
what does 100% saturation mean?
all haem groups of Hb molecules fully saturated with O2
what is used in clinic to measure O2 saturation?
pulse oximeters
how does a pulse oximeter measure O2 saturation?
measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
in normal healthy conditions what is the volume of CO2 produced per minute?
200ml/min, 80 molecules CO2 expired by lung for every 100 molecules O2 that enter
what is the respiratory exchange ratio?
CO2 expired to O2 uptake
what are the 3 forms of CO2 transport?
dissolved, bound to haemoglobin and as bicarbonate
what is the direction and speed of the carbon dioxide- bicarbonate reaction determined by?
the concentration gradients
what is the direction of the bicarbonate reaction in systemic capillaries?
rightwards (bicarbonate - carbon dioxide) CO2 produced by tissues is expelled into blood
what is the direction of the bicarbonate reaction in pulmonary capillaries?
leftwards (carbon dioxide - bicarbonate) CO2 to be expelled into alveoli
what can changes in the bicarbonate concentration be used to do?
stabilise the pH
how can acidity in the blood be regulated?
by using ventilation to adjust the PCO2 or by using the kidneys to regulate the bicarbonate concentration
what is the main point of the O2 dissociation curve?
above 60mmHg the increase of decreased PO2 has minimal effect on Hb saturation
what is the major transport system for O2?
within red blood cells bound to Hb
what is the major transport system for CO2?
within red blood cells in the form of bicarbonate
what does the carbon dioxide - bicarbonate pathway play a critical role in?
regulation of H+ ions and in maintaining acid-base balance in body
