RS. Gas Transport Flashcards
what does blood do in the pulmonary circuit?
o2 enters blood
co2 leaves
what does blood do in the systemic circuit?
o2 leaves blood
co2 enters
how does gas move throughout the respiratory system?
diffusion
what features of respiratory and circulatory systems facilitates 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 the mixture X barometric pressure
what 2 forms can oxygen be transported around the body?
- dissolved in the blood
- bound to haemoglobin
what is the amount of o2 dissolved in the blood proportional to?
its partial pressure
what is the typical partial pressure of o2 in arterial blood in a healthy individual?
100mm Hg
what is the cardiac output at rest (dissolved O2 transport)?
5 litres per minute
what is the basic tissue oxygen requirement at rest (dissolved o2 transport)?
250ml per minute
what is the major transport molecule for o2 found in red blood cells?
haemoglobin
what makes a global protein?
4 heme groups
how many haemoglobin molecules in a red blood cell?
280 million
how quickly does the binding and dissociation of o2 with Hb?
milliseconds
why does the binding and dissociation of o2 with Hb have to be very quick?
as red blood cells are in capillaries for only 1 second
what does the oxyhemoglobin dissociation curve illustrate?
relationship between PO2 in blood and number of O2 molecules bound to Hb
what factors effect the percent haemoglobin saturation by oxygen?
pH
temperature
what does a flat portion on the oxyhemoglobin dissociation curve suggest?
drop in PO2 from 100 to 60 mmHg has minimal effect on Hb saturation
what does a steep portion on the oxyhemoglobin dissociation curve suggest?
large amount of O2 is released from Hb with only a small change in PO2 facilitating into these tissues
is O2 binding to haemoglobin reversible or irreversible?
reversible
how many O2 atoms can bind to a single Hb molecule?
4
what does O2 saturation (SaO2) refer to?
amount of O2 bound to Hb relative to maximal amount that can bind
when is oxygen saturation at 100%?
all heme groups of Hb molecule are fully saturated with O2
how many ml of O2 combine with 1g of Hb?
1.39ml
what are pulse oximeters used for?
to measure O2 saturation
how do pulse oximeters work?
measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
what is the expiratory exchange ratio?
ratio of expired CO2 to O2 uptake
in normal conditions, what is the respiratory exchange ratio?
0.8
(80 CO2 to 100 O2)
in what 3 ways is CO2 transported?
- 7% dissolved
- 23% bound to haemoglobin
- 70% converted to bicarbonate
what is the waste product of cells and tissues?
CO2
when CO2 binds to HB what does it form?
carbaminohaemoglobin
when CO2 binds to HB what does it form?
carbaminohaemoglobin
what can the conversion of CO2 to bicarbonate affect?
the pH of blood
what is the buffer base bicarbonate equation to maintain balance in the blood?
systemic capillaries >
H2O+CO2 <> HCO3 <> H + HCO3
what is CO2 carried around the body as?
bicarbonate
the stronger bicarbonate concentration in the blood the buffering reaction is…
stronger
what are the major transport systems of O2 and CO2?
O2 = red blood cells bound to Hb
CO2 = red blood cells in the form of HCO3
what shape is the O2 dissociation curve?
s shaped
what does the CO2 to HCO3 pathway do in the body?
regulates H+ ions
maintain acid base balance
how do you measure lung volumes clinically?
take big inspiration then exhale as fast as possible
