3.4 Mass transport in animals Flashcards
What are 4 features of a transport system?
suitable medium in which to carry materials
a form of mass transport in which the medium is moved around in bulk over large distances
closed system of tubular vessels that contain medium and froms a branching network to distribute to all parts of the organism
a mechanism for moving medium within vessels - pressure differences
Why have multicellular organisms developed a circulatory system?
they cannot rely on diffusion alone to transport substances
what is mass flow?
molecules are carried in the flow of fluid, the flow is generated by a force which is produced by a pump
What are the 3 parts of a circulatory system?
transport fluid - plasma and tissue fluid
a pump - heart
series of tubes - vessels
What does closed, double circulatory system mean?
blood is confined to vessels and it passes through the heart x2 per 1 circuit
Why does blood pass through the heart twice?
when blood passes through the lungs, its pressure is reduced so the pressure needs to rise again
Why is exchange from blood vessels to cells rapid?
diffusion takes place over a large SA and a short distance and a steep diffusion grad
Which side of the heart transports oxygenated blood?
left
Which side of the heart transports deoxy blood?
right
What happens to oxygnated blood in a double ciculatory system?
oxy blood from gas exchange surface passes through the heart before going to the tissues
What happens during a single circulatory system?
blood passes through the heart once per cycle
only transports deoxy blood
oxy blood from gas exchange surface goes directly to tissues
What are the advantages of double ciculation?
prevents low blood pressures - blood pressures falls in the capillaries
better blood flow for O2 distribution for respiration
Why does pressure drop in the capillaries?
the dilation of the arterioles - increase in vol = decrease in pressure
What is pulmonary cicuit?
cirulation between the heart and lungs
lungs to heart - oxy blood via veins
heart to lungs - deoxy blood via arteries
What is systemic ciculation?
circulation between the heart and body tissues
heart - body tissues = oxy blood via arteries
body tissues - heart = deoxy blood via veins
What does the right side of the heart do?
pumps blood around the pulmonary circuit to re-oxygenate blood after returning from body tissues
body tissues –> vena cava –> right atrium and ventricle –> pulmonary artery
deoxy blood in right side, high in CO2
What is the vena cava?
a large vein that collects blood from the systemic circuit
What does the left side of the heart do?
pumps blood around the systemic cicuit to deliver O2 to respiring body tissues
oxy blood
pulmonary vein –> left atrium and ventricle –> aorta
What direction do veins usually carry blood?
towards the heart
What direction do arteries usually carry blood?
away from the heart
How does blood go into the coronary arteries?
by the aorta
Where is the CO2 produced by the heart drained?
into the cardiac veins
What are the atria?
they are thin-walled elastic chambers that recieve blood from the veins
Why do the atria have thin walls?
they need to be able to expand to fill up with more blood
What are ventricles?
thick-walled chambers that pump blood out of the heart through the arteries
Why are the ventricles thick walled?
they pump blood further distances so it needs a higher pressure to sustain this distance around the body
How are the artia and ventricle separated?
by atrio-ventricular valves
How are the artieries leading from the heart and the ventricles separated?
semi-lunar valves
How is the cardiac muscle different to other muscles?
it can contract without a signal from the brain - automatic contraction
What is cardiac muscle?
a specialised type of muscle found in the walls of the heart
What do the coronary arteries do?
they deliver O2 and nutrients to the heart tissue
What does the cardiac muscle consist of?
branched myofibrils which are separated by intercalated discs
What are all the structures of the heart? (top left to top right of the heart)
left pulomonary artery
pulmonary vein
left artium
semi-lunar valve
atrio-ventricular valve - bicuspid
left ventricle
tendon
papillary muscle
septum
right ventricle
atrio-ventricular valves - tricuspid
inferior vena cava
right atrium
right pulomonary artery
aorta
superior vena cava
What do valve tendons do?
prevents valves from inverting
Where does the blood return to the heart from the systemic circuit?
right side
superior vena cava and inferior vena cava
Where does blood leave the heart to the pulmonary circuit?
from the left pulmonary artery
Where does blood return from the pulmonary circuit?
the pulmonary veins
Where does blood leave to the systemic circuit?
the aorta
What does TS stand for?
transverse section
Why does the bicuspid valve need to be replaced and the tricuspid valve doesnt?
the left side of the heart is a stronger muscle and thicker walls
the bicuspid is exposed to higher pressures
What symptom would someone have in their bicuspid valve was failing?
oxy blood would not travel around the body - irregular heartbeat
causes a shortness of breath and fatigue
What is cardiac output?
the volume of blood pumped out of the heart per minute
What is the cardiac output equation?
cardiac output = stroke volume x heart rate
What is the stroke volume?
the volume of blood pumped by the left ventricle every heart beat
What do coronary veins do?
they return deoxy blood from the cardiac muscle tissue by the vena cava
What will blockages of the coronary arteries cause?
a heart attack = an area of the heart is deprived of blood therefore deprived of O2, the muscle cells are unable to respire
What is the cardiac cycle?
the sequence of events that occur in 1 heartbeat, consists of contraction and relaxation
What does systole mean?
contraction
What does diastole mean?
relaxation
What direction does blood flow?
down a pressure grad
What happens during atrial systole?
the volume of the atria decreases
the pressure of the artia increases
the blood flows from the atria to the ventricles
the AV valves are open - due to pressure grad from atria–> ventricles
the SL valves are closed - due to pressure grad from arteries –> ventricles ( pressure is higher in the arteries)
What happens during ventricular systole?
the volume of the ventricles decreases
the pressure in the ventricles increases
the blood flows from ventricles –> arteries
the AV valves are closed - due to pressure grad from ventricles to atria
the SL valves are open - due to pressure grad from ventricles –> artery
What happens during diastole?
the whole heart is relaxed
the volume of the heart increases
the pressure in the heart decreases
the blood fills all the chambers
the AV valves are open - due to pressure grad from atria to ventricles
the SL valves are closed - due to pressure grad from arteries to ventricles
How long is atrial systole?
0.2 secs
How long is ventricular systole?
on graph - 0.2 - 0.4 secs
so lasts 0.2 secs
How long is diastole?
on graph - 0.4-0.8
so lasts 0.4 secs
Where on the cardiac cycle graph do the valves open/ close?
when the lines intercept
What do the atrio-ventricular valves do?
prevent the backflow of blood when contraction of the ventricles means the ventricular pressure exceeds atrial pressure
What do the semi-lunar valves do?
they prevent the backflow of blood into the ventricles from the arteries when the pressure in the arteries exceeds the pressue in the ventricles
How does aortic pressure exceed the ventricular pressure?
when the elastic walls of the arteries recoil increasing their pressure and the ventricular walls relax and have lower pressure
What are pocket valves?
the valves in veins that ensure that when veins are squeezed, the blood flows towards the heart
What is the advantage of transporting blood in vessels?
it allows the blood to be pumped at high pressures delivering nutrients and removing waste more efficently
What are the 5 types of blood vessels?
arteries
arterioles
capillaries
venules
veins
What does the elastic tissue in blood vessels (arteries and arterioles) do?
expands and contracts to maintain blood pressure
What does the smooth muscle do in the artery?
keeps the arteries open and controls the lumen diameter by contracting and relaxing
What are capillairy walls made of?
single-celled and flattened (squamous) layer of endothelial cells
Why are capillaries thin?
for exchange - short diffusion pathway
Why do capillaries have a narrow lumen?
can squeeze rbc against the endothelium to improve the transfer of O2 - shortens diffusion distance
why is the vein lumen wide?
allows max blood flow and get deoxy blood back to the heart as fast as possible
What is the relationship between the total cross-sectional area and rate of flow?
indirectly proportional - as tot cross-sec increases, the rate of flow decreases
What is the decrisption of the total cross sectional area on the blood vessels graph?
it increases going away from the heart and is at its highest in the capillaires
decreases coming back towards the heart
What is the decrisption of the rate of flow on the blood vessels graph?
it decreases aorta –> arterioles
lowest at capillaries - allows time for exchange
increases venules –> vena cava
What is the decrisption of the blood pressure on the blood vessels graph?
it is highest in the aorta and arteries
fluctuates rhythmecally - due to pulse
falls continuesly as blood goes away from the heart
it never falls to 0 = the semi-lunar valves close
What is the relationship of the total cross sectional area and the surface area?
the SA decreases, the tot cross sec increases
What happens when friction increases inside the blood vessels?
the pressure falls and the flow rate slows
Describe an arteries lumen
has a narrow diamter in relation to tot diameter therefore a high resistance to blood flow which maintains pressure
Describe the arteries elastic tissue
thick elastic tissue layer in walls to allow walls to expand with each pulse of blood and then return to original shape - called elastic recoil
this evens out blood flow and maintains a high pressure
Describe the arteries muscle layer
thick smooth elastic layer in walls which can contract /relax altering blood pressure
Which arteries have valves?
aorta and pulmonary artery
Describe a veins lumen
wide lumen in relation to diameter therefore less resistance to blood flow which helps blood return to the heart
describe veins muscle layer
thin smooth muscle layer in walls. less muscle to contract so will not narrow lumen to resist blood flow
describe veins elastic layer
thin elastic tissue layer in walls. as there is no need to expand with each pulse of blood therefore no need for elastic recoil - there isnt a high pressure
Why do the veins thin walls aid blood flow?
they can be flattened easily by muscles forcing blood to return to the heart
What valves do veins have?
semi-lunar valves to prevent backflow of blood caused by low blood pressure
describe a capillaries lumen
narrow lumen casues and increase in tot cross sec so more surface is in contact with blood, causing greater friction between blood and capillary wall
results in loss of blood pressure
Why do capillaries have pores?
they have fenerstrations - making it permeable so small molecules can filter out
What does the tough fibrous outer layer do in blood vessels?
resists pressure changes from both within and outside
What does the thin inner lining (endothelium) do in blood vessels?
smooth to reduce friction and thin to allow diffusion
How do capillaries have a large SA for exchange?
dense network
How do capillaires have a short diffusion pathway for exchange?
single layer of endothlial cells
flattened endothelial cells
rbc in contact with walls
narrow lumen causes rbc to pass in single file
How do capillaries allow formation of tissue fluid?
fenerstrations between endothelial cells
What is venous return?
blood returning to the heart by the vena cava
How is the blood returned to the heart by the suction effect?
during atria diastole there is a low pressure in the atria so the blood moves towards the heart down a pressure gradient
How is blood returned to the heart by the skeletal muscles?
When the skeletal muscles contract it increases the pressure in the veins - forces blood through the valves and blood to return to the heart
the valves then close again to prevent back flow
How is blood pressure maintained in the arteries during systole?
the structure:
the elastic fibres can expand and enable blood flow to withstand pressures during systole
How is blood pressure maintained in the arteries during diastole?
when pressure falls - the elastic fibres recoil to maintain high pressures
What are the blood’s functions?
specialised transport medium
the immune system
thermoregulation
maintains pH of body fluids
What are the two main things blood is made of?
45% cells
55% plasma
What is in the cells part of the blood?
erythrocytes (RBC) for transport O2
Leukocytes (WBC) for immune system
thrombocytes (platelets) for clotting
What is in the blood plasma?
water (92%)
plasma proteins (enzymes, antibodies)
ions (K+, Na+, Cl-, Ca2+)
nutrients (glucose, amino acids)
waste (urea)
hormones
gases
Why does a erythrocyte have a flattened biconcave shape?
large SA:VOL for increased efficiency of O2 exchange
Why don’t erythrocytes have a nucleus or organelles?
more room for heam therefore more O2 can be transported
Why is the diamter of a erythrocyte larger than a capillaries diameter?
RBC has to squeeze through capillary - short diff pathway
slows down RBC for more time for exchange
How is the high hydrostatic pressure created at the arterial end of the capillary?
ventricular systole and elastic recoil in arteries maintains pressure
vol decreases arteriole -> capillary
How is tissue fluid formed?
high hydrostatic pressure at arterial end of the capillary
ultrafiltration of small molecules - through fenerstrations in the capillaries
large molecules and some water stays in the capillary
What is tissue fluid?
the fluid containing water, glucose, amino acids, fatty acids, ions and O2 which bathes the tissues
Why dont blood cells or plasma proteins leave the capillary during untrafiltration?
too large to fit through capillary fenertrations
What happens as blood flows through the capillary after forming tissue fluid?
there is a decrease in water potential as there is a high conc of plasma proteins in the blood
water is pulled back into the capillary ar the venous end
How do cells take up lipid soluble molecules and gases?
simple diffusion
How do cells take up glucose?
active transport
How is tissue fluid reabsorbed into the blood?
at the venous end of the capillary
large molecules remained in the capillary create a lower water potential - water re-enters by osmosis
theres a lower hydrostatic pressure as the liquid was lost - dissolved waste molecules enter
Why isnt all tissue fluid reabsorbed?
an equilibrium will be reached
What happens to excess tissue fluid?
called lymph
drained into the lymphatic system and is eventually drained back into the bloodstream near the heart
How are the contents of the lymphatic system moved?
contraction of muscles - squeezes lymph vessels - valves ensure it moves towards the heart
What is the structure of a lymph vessel?
single layer of overlapping epithelial cells
valves - ensures uni-directional flow
blind-ended - ensures uni-directional flow
How does lymph return to the blood?
via the thoratic duct or the subclavian vein
What are the vessels connecting the heart and liver called?
the heptic vein and artery
What is a risk factor?
something that increases the likelihood of developing a disease
What are the forces opposing the high hydrostatic pressure of tissue fluid leaving the blood?
high hydrostatic pressure of tissue fluid outside of the capillaries prevents the outward movment of the liquid
lower water potential of the blood - pulls water back into the capillaries
What is lymph made of?
tissue fluid
fatty substances
lymphocytes
What are the 4 subunits haemoglobin is made of?
x2 alpha and x2 beta subunits
What is 1 subunit made of in haemoglobin?
a polypeptide chain and a Fe2+ ion (haem group)
Where does O2 associate in haemoglobin?
to the haem group
What is oxyhaemoglobin?
a fully saturated haemoglobin
HbO8 - 4O2 per haemoglobin
How are there different haemoglobins?
have different shapes in different species due to the different amino acid sequences
When does haemoglobin’s affinity for O2 change?
under different conditions - it will chnage its shape in the presence of certain substances
Where does oxygen associate to hb?
in the alveoli - high O2 conc in the tissue - high partial pressure of O2 = high affinity of O2 - O2 binds tightly
Where does O2 dissociate from hb?
respiring tissues - low O2 conc in tissue as it is used in aerobic resp = low pO2 = low affinity for O2 = dissociation
What are the steps of co-operative binding?
it is difficult for the first O2 to bind as it is difficult to reach the haem group - polypeptide chains are packed tightly at low pO2
when the 1st O2 binds, the hb changes shape + opens up polypeptide chains
makes it easier for next O2 to bind
the last O2 is the easiest to bind but a large pO2 is needed for all hb to be saturated
What does the top of the O2 dissociation curve show?
high pO2 - in the alveoli
high levels of O2
high % saturation of O2 - high affinity for O2 - can readily dissociate
What does the middle of the O2 dissociation graph show?
smll chnage in pO2 = large change in % saturation:
a small increase in resp rate = small decreases in pO2 of blood
causes a large decrease in % saturation
so more O2 is supplied to the tissues so the rate of resp can be maintained
What does the bottom of the O2 dissociation curve show?
low pO2 - resp muscle cells
low % saturation = low affinity for O2
What is oxyhaemoglobin?
all haem groups are bound to O2 - it is saturated
What does a left shift of the O2 dissociation graph mean in terms of affinity for O2?
increases affinity for O2
in a low O2 environment
What does a right shift of the O2 dissociation graph mean in terms of affinity for O2?
decreased affinity for O2
increase pCO2
decreased pH
What causes the Bohr effect (right shift)?
high pCO2 due to activity - anerobic resp in muscle tissues
increased pCO2 in blood
lowers the pH of the blood
reduces affinity of hb for O2
more O2 being unloaded at the same pO2
more O2 being released to the tissues overall
tissues can maintain increased rate of aerobi resp
What causes the left shift dissociation curve (llama and foetus)?
low pO2 conditions (mountains/ underground/ in womb)
hb has adapted high affinity for O2
acheives high % saturation at low pO2
so O2 can be unloaded to tissues at low PO2
maintains aerobic resp in low pO2 environment
What is the advantage of organisms living in low O2 environments having adapted haemoglobin?
it can still associate with O2 with little O2 in the air and acheive high % saturation and unload O2 to resp tissues
Describe the structure of haemoglobin
a globular protein made up of 2 alpha chains and 2 beta chains
each chain folds and contains a haem group which contains iron ions where oxygen binds
What is partial pressure?
the pressure a gas exerts in a mixture of gases
Explain the Oxygen dissociation graph in terms of how an O2 molecule binds to haemoglobin
- initially the curve is shallow = it is hard for the first molecules to bind
- steep increases = hb changes shape and easier to bind (positive cooperativity)
- gradient flattens = the liklihood that the 4th O2 binds is low
Explain the effect of CO2 concentration on the dissociation curve
increasing CO2 decreases haemoglobin’s affinity for O2
increasing CO2 = increases acidity = changes shape of haemoglobin protein = easier for O2 to be released
What are all the structural features of the aorta?
smooth and thick muscle walls
elastic tissue stretches and recoils
smooth endothelium
muscular walls
aortic valve
protein coat
narrow lumen
What is the function of the smooth muscle in the aorta?
WITHSTANDS high blood pressure
What is te function of the elastic tissue/recoil in the aorta?
smooths blood flow and MAINTAINS blood pressure
What is the function of the smooth endothelium in the aorta?
reduces friction
What is the function of the aortic valve in the aorta?
prevents backflow of blood
What is the function of the protein coat in the aorta?
prevents the artery wall splitting
What is the function of the narrow lumen in the aorta?
high resistence to blood flow to maintain pressure
Why would you need to stain red blood cells to observe them under an optical microscope?
red blood cells do not have a nucelus so they are not seen under the microscope unless stained
