gas exchange and transport

Question 1

purpose of respiration

Answer 1

remove oxygen from the air for use at the body tissues, remove CO2 from body tissues and eliminate it in expiration

Question 2

respiration

Answer 2

external- exchange of oxygen and CO2 at the alveoli, internal- exchange of oxygen and co2 at the tissue
atmospheric air- nitrogen, oxygen, water, co2

Question 3

Partial pressure- daltons law

Answer 3

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

Question 4

units for gas pressure

Answer 4

American text and paediatrics use mmHg (millimetre of mecurary), English texts and adults use Kpa (kilopascales), KPA= mmHg/7.5, mmHg- KPA*7.5

Question 5

henrys law

Answer 5

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

Question 6

movement of oxygen

Answer 6

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

Question 7

conducting zone and respiratory zone

Answer 7

conducting- nose, phalanx, larynx, trachea, bronchi, bronchioles, terminal brochioles
respiratory- respiratory bronchioles, alveoli ducts, alveoli sacs

Question 8

what is diffusion

Answer 8

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

Question 9

factors controlling rate of diffusion

Answer 9

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

Question 10

what is diffusion proportional to

Answer 10

SA*difference in concentration/ diffusion distance

Question 11

influencing factors to diffusion

Answer 11

temp- increase in temp- increase in diffusion, movement of molecules, partial pressure of the gas in the 2 area s

Question 12

alveolar oxygen exchange

Answer 12

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

Question 13

how does haemoglobin contribute to PP

Answer 13

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

Question 14

oxygen and the alveoli/ capillary interlace

Answer 14

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

Question 15

carbon dioxide and the alveoli/ capillary interlace

Answer 15

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

Question 16

capillary and tissue interlace

Answer 16

bulk flow of blood to tissues. diffusion through RBC wall, through plasma, through capillary wall, through tissue membrane, into mitochondria, CO2 goes other way

Question 17

oxygen exchange during exercise

Answer 17

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

Question 18

oxygen exchange in disease

Answer 18

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

Question 19

red blood cells

Answer 19

disc shaped- thin in middle and thicker at edges (biconcave disc), lack nuclei, mitochondria and ribosomes, contain haemoglobin

Question 20

haemoglobin- normal values and structure

Answer 20

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

Question 21

how does haemoglobin work

Answer 21

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

Question 22

oxygen dissociation curve

Answer 22

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

Question 23

release of oxygen at the tissues

Answer 23

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

Question 24

oxygen dissociation curve- COPD

Answer 24

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

Question 25

factors affecting dissociation- temperature

Answer 25

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

Question 26

factors affecting dissociation- PP of co2

Answer 26

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

Question 27

factors affecting dissociation- pH

Answer 27

affects binding site

Question 28

factors affecting dissociation- 2,3- diphosphoglycerate

Answer 28

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

Question 29

factors affecting dissociation- anaemia

Answer 29

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

Question 30

how CO2 transported

Answer 30

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%),

Question 31

what is the Hednerson Hasselback equation

Answer 31

H20+CO2===H2C03====H+HC03
water + C02=== carbonic acid- hydrogen ion and bicarbonate ion
requires the enzymes carbonic anhydrase

Question 32

Bohr effect

Answer 32

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

Question 33

Bohr effect- what effect does this have at the tissues

Answer 33

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

Question 34

Bohr effect- lungs

Answer 34

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

Question 35

haladene effect

Answer 35

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

Question 36

acid base balance

Answer 36

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