(7) Mass transport Flashcards
what is the process by which haemoglobin binds with oxygen and where does it take place
loading/ associating and takes place in the lungs
what is the process by which haemoglobin releases oxygen and where does this take place
unloading/ dissociating and takes place in the tissues
what is the difference between haemoglobin with high/low affinity for oxygen
high affinity for oxygen takes up oxygen more easily but release it less easily. haemoglobin with low affinity for oxygen take up oxygen less easily but release it more easily
what are 2 conditions for haemoglobin to be efficient
1) must readily associate with oxygen at the surface where gas exchange takes place (alveoli that have a high pO2)
2) readily dissociates from oxygen at the tissues requiring it
as these are contradictory- haemoglobin can change its affinity under different conditions
what happens to haemoglobin in the presence of carbon dioxide
it changes shape and the new shaped molecule binds more loosely to oxygen meaning the haemoglobin releases its oxygen
how many oxygen molecules can a haemoglobin molecule carry
4
what is partial pressure of oxygen
a measure of oxygen concentration that is higher when there is a greater concentration of dissolved oxygen in cells
how does oxygen partial pressure affect loading and unloading
a high pO2 means O2 loads onto haemoglobin to form oxyhaemoglobin and when there’s a low pO2, haemoglobin unloads it’s oxygen
what conditions do tissues have that allow oxygen to be unloaded
they have a low pO2 due to the respiring cell using up oxygen which lowers pO2
what does a dissociation curve show
how saturated the haemoglobin is with oxygen at any given partial pressure
why is an oxygen dissociation curve S shaped
when Hb combines with the first O2 molecule its shape alters in a way that makes it easier for other molecules to join too. As the Hb starts to become saturated it gets harder for more O2 molecules to join
what is the Bohr effect
haemoglobin gives up its oxygen more readily at higher partial pressures of CO2. respiring cells produce CO2 which increases the rate of O2 unloading so dissociation curve shifts right
what is the circulatory system made up of
heart and blood vessels
what are arteries
vessels that carry blood from the heart to the rest of the body. thick and muscular walls with elastic tissue to stretch and recoil as the heart beats to help it maintain high pressure. the endothelium is folded so artery can stretch. carry oxygenated blood
what are arterioles
arteries divide into smaller vessels called arterioles. muscles in the arterioles direct blood to different areas of demand by contracting to restrict blood flow or relaxing to allow it
what are veins
take blood back to heart under low pressure. wide lumen with little elastic or muscle tissue. contain valves to prevent backflow. carry deoxygenated blood
what is the exception with pulmonary arteries and veins
pulmonary veins carry oxygenated blood to the heart from the lungs.
pulmonary arteries carry deoxygenated blood to the lungs
what are capillaries
arterioles branch into capillaries (smallest blood vessel) they’re adapted for efficient diffusion as glucose and oxygen are exchanged between cells and capillaries. only one cell thick. large number of them to increase SA for exchange
what is tissue fluid
fluid that surrounds tissue cells. made from small molecules that leave blood plasma eg O2, H2O and nutrients (doesn’t contain RBC’s or big proteins)
in a capillary bed, how do substances move out of the capillaries and into the tissue fluid by pressure filtration
1) hydrostatic pressure in the capillaries is greater than in the tissue fluid at the start of the capillary bed
2) an overall outward pressure forces fluid out of the capillaries and into spaces around cells forming tissue fluid
3) hydrostatic pressure reduces in the capillaries (much lower at the venule end)
4) water potential at venule end is lower than in the tissue fluid due to fluid loss and ever increasing conc of plasma proteins
5) some water re enters capillaries from tissue fluid at venule end by osmosis
what happens to excess tissue fluid
it is drained into the lymphatic system which transports it back into the circulatory system
what are the roles of the left and right sides of the heart
right side- pumps deoxygenated blood to the lungs
left side- pumps oxygenated blood to the whole body
difference between left and right sides of the heart
left ventricle has thicker and more muscular walls than the right ventricle because it needs to contract to pump blood around the whole body rather than just the lungs.
why do the ventricles have thicker walls than the atria
ventricles have to push blood out of the heart whereas atria just push blood a short distance into the ventricles
