gas exchange and transport Flashcards
purpose of respiration
remove oxygen from the air for use at the body tissues, remove CO2 from body tissues and eliminate it in expiration
respiration
external- exchange of oxygen and CO2 at the alveoli, internal- exchange of oxygen and co2 at the tissue
atmospheric air- nitrogen, oxygen, water, co2
Partial pressure- daltons law
the partial pressure of a gas is the pressure contributed by a single gas in a mixture of gases. the mixture of gases exerts a pressure which is the sum of the partial pressure of all the individual gases
units for gas pressure
American text and paediatrics use mmHg (millimetre of mecurary), English texts and adults use Kpa (kilopascales), KPA= mmHg/7.5, mmHg- KPA*7.5
henrys law
the amount of gas in solution depends on the partial pressure of the gas and its solubility. Co2 In air has a low partial pressure but high solubility, oxygen has lower solubility but a higher partial pressure
movement of oxygen
oxygen moves along the conducting zone by bulk flow, in the respiratory zone, oxygen moves by diffusion. oxygen dissolves in and diffuses through surfactant, alveolar wall and the capillary wall into the plasma
conducting zone and respiratory zone
conducting- nose, phalanx, larynx, trachea, bronchi, bronchioles, terminal brochioles
respiratory- respiratory bronchioles, alveoli ducts, alveoli sacs
what is diffusion
movement of gas molecules from an area where the gas exerts a high partial pressure to an area where it exerts a low partial pressure
factors controlling rate of diffusion
area of the barrier- larger is better, diffusing ability of the gas- how well it can dissolve, inversely proportional to the thickness of the barrier- thicker= less diffusion, partial pressure difference- greater the difference= better diffusion
what is diffusion proportional to
SA*difference in concentration/ diffusion distance
influencing factors to diffusion
temp- increase in temp- increase in diffusion, movement of molecules, partial pressure of the gas in the 2 area s
alveolar oxygen exchange
venous blood contains 40mmHg PP O2, alveoli air contains 104mmHg PP O2, the movement of oxygen from the alveoli to the venous blood occurs, equilibrium takes about 0.25 secs
how does haemoglobin contribute to PP
oxygen combined with haemoglobin does not contribute to the PP within capillary blood. once the haemoglobin is saturated, oxygen collects in the plasma and contributes to its PP, which then equals the alveolar pp. Here the transfer of oxygen is perfusion limited- lack blood supply
oxygen and the alveoli/ capillary interlace
dissolves in and diffuses through surfactant. through the alveolar wall, through the capillary wall, into plasma, into RBC and combines with haemoglobin, co2 goes the other way
carbon dioxide and the alveoli/ capillary interlace
mixed venous blood contains 45mmHg partial pressure of C02, alveolar partial pressure of co2 IS 40MMhG. Small gradient between the 2 PP, CO2 is more soluble and reaches equilibrium in 0.25secs
capillary and tissue interlace
bulk flow of blood to tissues. diffusion through RBC wall, through plasma, through capillary wall, through tissue membrane, into mitochondria, CO2 goes other way
oxygen exchange during exercise
blood moves quickly through the capillaries. no limbs on diffusion or perfusion as capillaries are recruited. PP are maintained, deep breaths- more alveoli recruited, heart pumps harder- increase CO and perfusion
oxygen exchange in disease
patients with abnormal alveolar/ capillary interlace e.g. fibrosis and oedema. thickness of the barrier has increase- extra sputum. diffusion of oxygen is reduced. may suffer diffusion limitation at rest which limits exercise tolerance
red blood cells
disc shaped- thin in middle and thicker at edges (biconcave disc), lack nuclei, mitochondria and ribosomes, contain haemoglobin
haemoglobin- normal values and structure
14-18 in males (140-180g/L), 12-16 in females (120-160g/L)
structure- 2 alpha polypeptide chains, 2 beta polypeptide chains, each chain forms a protein subunit with a single heme molecules
how does haemoglobin work
98.5% if blood transported by haemoglobin (1.5% in dissolved plasma), combines reversibly with oxygen, deoxyhaemoglobin/ oxyhemoglobin (HHb+O2/ Hb02+H), the amount of O2 bound to Hb is known as %saturation, %haemoglobin saturation- oxygen bound to Hb/ oxygen capacity of Hb X 100, conditions that affect haemoglobin saturation- anaemic- affects relationship- affects exercising
oxygen dissociation curve
the 4 subunits on Hb molecules react with oxygen in sequence not simultaneously. dissociation occurs in a similar sequence. the X axis= Pp of 02, Y axis= saturation of haemoglobin, mixed venous blood has a PP of oxygen 40mmHg, at this level Hb is 75% saturated oxygen. at 70mmHg, Hb is 94.1% saturated where the curve has flattened out, at 100mmHg PP of oxygen, Hb is 97.4% saturated with oxygen
release of oxygen at the tissues
dissociation curve is steep between 2- and 40mmHg, a small decrease in oxygen within the tissue results in a substantial unloading of oxygen from the blood
oxygen dissociation curve- COPD
patient with COPD- leads to less O2 being delivered into the plasma and alveoli level and % saturated will be less. this might be gone is a resting situation but if we exercise/mobilise a patient they are on a seep part of a graph where o2 will want to off load from Hb in appropriately- patients won’t have enough O2
factors affecting dissociation- temperature
a higher temp will encourage hb to give up O2 and vice versa, so when exercising working tissues which are metabolically active will create an environment of higher temp will get the O2 off Hb and be ablee to be uses by the tissue- curve shift to right
factors affecting dissociation- PP of co2
Co2 increases in tissues when they are working which again, shifts the curve to the right and there is an encouragement of Hb to give up its O2. as co2 will want to blind the Hb and whilst the 2 O2 compete for a binding site is altered when CO2 is attached which makes it less attractive to O2
factors affecting dissociation- pH
affects binding site
factors affecting dissociation- 2,3- diphosphoglycerate
is a protein produced by RBC and it binds to hb again on different site of O2 but I doing so it decreases Hb and O2 affinity. the RBC produce it in response to detection of lower O2
factors affecting dissociation- anaemia
less Hb for O2 to bind with, carbon monoxide- blocks O2 binding site on hb and blocks it so no O2 can ge ton and nitric oxide- inhibits Hb and O2 affinity but in a different way
how CO2 transported
20 times more soluble than oxygen. carried in solution in plasma (5-10%), chemically bound to amine acids (5-10%), as bicarbonate ions (80-90%),
what is the Hednerson Hasselback equation
H20+CO2===H2C03====H+HC03
water + C02=== carbonic acid- hydrogen ion and bicarbonate ion
requires the enzymes carbonic anhydrase
Bohr effect
effect of Ph on the dissociation curve, an excess of hydrogen ions leads to a low pH, deoxyhaemoglobin are readily access the hydrogen ions/ this shifts the oxygen dissociation curve to the right. oxyhemoglobin is facilitated to release its oxygen. this occurs at high c02 levels due to- CO2+H20=H2C03=H+HCO3
Bohr effect- what effect does this have at the tissues
CO2 moves from the tissues into the plasma. most enters the RBC and some combines with Hb and the rest combines with H20 to form H+HCO3. HC03 moves into plasma and acts as a plasma. H combines with HBO2 ti release O2 to form HHB. O2 moves into tissue
Bohr effect- lungs
O2 moves from alveoli into plasma. most moves into RBC and forms HBCO2 and CO2. the CO2 moves to alveoli H combines with HCO3 to form H20 and CO2. the C02 moves to alveoli. CO2 dissolved in plasma moves into the alveoli and Hb release CO2 as well
haladene effect
oxyhemoglobin presence facilitates the movement of CO2 out of the blood (e.g. at the lungs). the presence of deoxyhaemoglobin facilitates more co2 to be carried by the blood (e.g. at the tissues
acid base balance
hydrogen ions are being continually produced through metabolism, they are regulated by hydrogen ion excretion by the kidneys and CO2 excretion by the lung. accumulation of CO2 leads to an increase in hydrogen io production and fall in blood Ph causing respiratory acidosis
