Transport in Animals Flashcards
What are the 5 reasons animals need specialised transport systems?
- high metabolic demands
- sa:vol ratio is smaller so larger diff. distances and smaller sa to absorb/ remove substances
- hormones/ enzymes made in one place, needed in another
- food needs to be transported to every cell for use in respiration and cell metabolism
- waste products of metabolism need to be removed from cells and transported to excretory organs
mass flow
movement of fluids down a pressure or temperature gradient
diffusion
net movement of particles from a region of higher concentration to a region of lower concentration
circulatory system
transport system carrying gases, nutrients, waste products, hormones around the body
common features of circulatory systems
- liquid transport medium (blood)
- vessels carrying transport medium
- pumping mechanism to move the fluid around the system
open circulatory system
circulatory system with a heart but few vessels to contain the transport medium
haemocoel
- body cavity in an open circulatory system
- transport medium under low pressure
- comes into direct contact with tissues and cells
in the haemocoel the transport medium is under …… pressure
low
in what type of animals are open circulatory systems often found?
invertebrates (most insects and molluscs)
haemolymph
the transport medium (blood) in insects
closed circulatory system
circulatory system where blood is enclosed in blood vessels and does not come into direct contact with the cells of the body beyond the blood vessels
in what type of animals are closed circulatory systems often found?
all vertebrate groups (incl. mammals)
echinoderms
cephalopod molluscs
single circulatory system
circulatory system where the blood flows through the heart and is pumped out to travel all around the body before returning to the heart
double circulatory system
circulatory system where blood travels twice through the heart for each complete circulation of the body.
1st - blood from heart -> lungs
2nd - ox blood from heart -> brain & r.o. body
what limits the efficiency of single circulatory systems?
- blood has to pass through 2 very narrow capillary vessels
- blood pressure in the system drops really low so blood returns slowly to the heart
- > reduced efficiency of exchange processes
- > usually only animals with low activity levels
how can fish be so active and yet have a single closed circulatory system?
- system relatively efficient
- countercurrent gas exchange in gills
- body weight supported by water they live in
- do not maintain their own body temp
what is the function of elastic fibres in the blood vessels?
can stretch and recoil
provide vessel walls with flexibility & enable it to withstand force of blood leaving heart
what is the function of smooth muscle in the blood vessels?
contract or relax
change the size of the lumen to control flow of blood
what is the function of collagen in the blood vessels?
structural support
maintains shape and volume of the vessel
artery structure
- walls have collagen outer layer, smooth muscle and elastic fibres.
- lined by smooth endothelial cells and have
- small lumen
arteries mostly carry …….. blood except in the ……
oxygenated blood pulmonary artery (umbilical artery in pregnancy)
which blood vessel is under the most pressure?
arteries
how is a continuous flow of blood achieved in the arteries?
elastic fibres recoil and return to their original length in between contractions of the heart. Helps to even out surges of blood pumped from heart and gives continuous flow
arterioles link
arteries and capillaries
arteriole structure
arterioles have more smooth muscle and less elastin in their walls than arteries
- little pulse surge
- can constrict or dilate to control flow of blood into individual organs
(both have collagen)
vasoconstriction. what do the arterioles do?
smooth muscle in arteriole wall contracts and prevents blood flowing into a capillary bed.
vasodilation. what do the arterioles do?
smooth muscle in the arteriole wall relaxes and blood flows freely into capillary bed
what do capillaries link?
arterioles and venules
diameter of capillary lumen
7-8um
how are capillaries adapted for their function?
- large SA for diffusion of gases into and out of blood
- walls are 1 endothelial cell thick, so short diff. distance
- blood flow through capillaries is slow to increase time for exchange of materials between blood and cells
3 adaptations that enable the body to return low pressure blood to the heart against gravity
- most veins have 1 way valves at intervals to prevent backflow of blood by closing when it flows the wrong way
- muscles contract and squeeze the veins, forcing blood towards the heart
- breathing movements of the chest act as a pump (pressure changes and squeezing actions move blood in the veins of the chest and abdomen towards the heart)
what type of cells make up capillaries?
flattened endothelial cells
pulmonary artery transports…
deoxygenated blood from the heart to the lungs
pulmonary vein transports…
oxygenated blood from the lungs towards the heart
inferior vena cava transports…
deoxygenated blood from the lower body to the heart
superior vena cava transports…
deoxygenated blood from the head and upper body to the heart
blood pressure in the veins is relatively
low
what do some medium sized veins have to prevent the back flow of blood
valves
vein structure
- walls have lots of collagen in outer layer, smooth muscle and little elastic fibre.
- lined by smooth endothelial cells
- wide lumen
venules link
capillaries to veins
venule structure
- very thin walls
- a little smooth muscle
- no elastin or collagen
why are there gaps between endothelial cells in capillaries (apart from in CNS)?
to allow substances to pass from capillaries into tissue fluid
what does plasma carry?
dissolved substances:
- glucose
- amino acids
- mineral ions
- hormones
- large plasma proteins
- erythrocytes
- leucocytes
- platelets
what are some examples of large plasma proteins?
- albumin maintains osmotic potential of blood - fibrinogen blood clotting - globulins transport and immune system
platelets
- fragments of large cells called megakaryocytes (found in red bone marrow)
- involved in blood clotting
blood transports (7)
- O2 and CO2 to and from respiring cells
- digested food from small intestine
- nitrogenous waste products from cells to excretory organs
- chemical messages (hormones)
- food from storage molecules to cells that need em for resp.
- platelets to damaged areas
- cells & antibodies involved in immune response
what canNOT pass through the gaps between endothelial cells in the capillary walls?
large plasma proteins
large plasma proteins have an ……. effect
osmotic
what is oncotic pressure in the capillaries and why does it occur?
tendency of water to move by osmosis from surrounding tissues into the capillaries
due to the low Ψ of capillaries as large plasma proteins have an osmotic effect so cause high solute potential in capillaries
what is hydrostatic pressure?
pressure that occurs every time heart contracts due to surge of blood through arterioles into capillaries
why is fluid squeezed out of the capillaries at the arterial end?
hydrostatic pressure > oncotic pressure
what % of tissue fluid is returned to the blood capillaries at the venus end? what happens to the fluid that does not return to the blood?
90
goes to the lymph
what is not in the tissue fluid that is in the blood plasma?
erythrocytes
large plasma proteins
why is fluid returned to the capillaries at the venus end?
oncotic pressure > hydrostatic pressure
oncotic pressure remains the same but hydrostatic pressure is lost as fluid has moved out of blood vessels and pulse has been completely lost
difference between lymph and tissue fluid
less O2
fewer nutrients
has fatty acids
how is the fluid transported through the lymph?
squeezing of body muscles
what prevents the backflow of lymph in the lymph capillaries?
one-way valves
where does the lymph return to the blood?
right and left clavical veins
what do lymph nodes do?
where lymphocytes mature
- intercept bacteria and other debris from lymph which are ingested by phagocytes found in the nodes
what happens to the lymph nodes in appearance when the body is fighting off infection?
they are enlarged
carbonic acid (H2CO3) breaks up into
H+ + HCO3-
what does haemolymph do?
carries
- food
- nitrogenous waste products
- cells involved in immune response
Name of the enzyme which helps turn CO2 and H2O into carbonic acid, and also catalyses the reverse reaction
carbonic anhydrase
The majority of carbon dioxide is carried as ….. in the plasma.
hydrogen carbonate ions (HCO3-)
Describe and explain what happens to the blood plasma in a capillary as hydrostatic pressure decreases (3)
plasma / fluid, moves out of, capillary / blood;
enters / forms, tissue fluid;
(plasma) proteins, remain in capillary / too large to pass through capillary wall / AW;
(fluid moves) down pressure gradient;
hydrostatic pressure greater than, water potential / Ψ;
Explain why the hydrostatic pressure of the blood drops as blood moves away from the heart. (2)
more, (smaller) vessels / named vessels;
(vessels) have larger, total lumen / cross sectional area; reduced resistance to blood flow;
arteries, stretch / expand;
loss of, fluid / plasma, from capillaries;
DO NOT CREDIT further from the heart
Blood in the arteries has a high hydrostatic pressure.
State how this hydrostatic pressure is generated in the heart. (1)
contraction of ventricle wall/ muscle;
State three ways in which the wall of an artery is different from the wall of a vein. (3)
artery has smaller lumen;
artery has no valves;
artery endothelium / tunica intima, folded / AW;
more / thicker, muscle / elastic tissue / tunica media;
more / thicker, collagen / tunica externa;
What are the adaptations of erythrocytes for transporting oxygen?
- biconcave shape to maximise SA for diffusion of gases and allow RBC to pass through narrow capillaries
- mature RBC have no nuclei to maximise space for Hb
- contain Hb proteins, each of which can bind to 4 O2 molecules
where are erythrocytes made in an adult?
red bone marrow
made continuously
why do erythrocytes only have a lifespan of 120 days?
they lose their nuclei to save space for Hb
what is the equation for the reaction between Haemoglobin and oxygen? What is made?
Hb + 4O2 ⇌ Hb(O2)4
haemoglobin + oxygen ⇌ oxyhaemoglobin
why does oxygen move from the alveoli of the lungs to the haemoglobin in RBC?
steep conc gradient between erythrocytes in capillaries and air in alveoli for oxygen
what is positive cooperativity?
as soon as one oxygen molecule binds to a haem group, the molecule changes shape, making it easier for the next oxygen molecules to bind
how is a steep conc gradient maintained after the first O2 molecule binds with Hb until it is completely saturated?
free oxygen concentration in erythrocyte stays low as oxygen is bound to Hb
- so steep diff gradient is maintained until all Hb are saturated with O2
what is the symbol for partial pressure of oxygen
pO2
what are on the two axis when you plot an oxygen dissociation curve?
x -partial pressure of oxygen (kPa)
y - percentage saturation of haemoglobin with oxygen (%)
What is the Bohr effect/shift?
as the partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more readily
Why is the Bohr effect important?
- in active tissues with a high partial pressure of CO2, Hb gives up its oxygen more readily
- in the lungs where the proportion of CO2 is relatively low, oxygen binds to Hb molecules more easily
What is the Bohr shift? ie. what happens to the oxygen dissociation curve when there is a low partial pressure of CO2?
the curve shifts to the right as haemoglobin gives up its oxygen more readily
fetal haemoglobin has a ……… affinity for oxygen that adult haemoglobin
higher
what is the significance of the high affinity of fetal haemoglobin for oxygen?
there is a concentration gradient created in the placenta between the fetal haemoglobin and the mother’s haemoglobin, meaning that oxygen is removed from the mother’s blood to supply the baby with O2
what happens to the oxygen dissociation curve for fetal Hb compared to adult Hb
fetal Hb shifts to the left as it gains oxygen more readily
How is CO2 transported from the tissues to the lungs? (3 different ways)
- 5% dissolved in plasma
- 10-20% combines with amino groups in the polypeptide chains of Hb to form carbaminohaemoglobin
- 75-85% converted into HCO3- ions in the cytoplasm of red blood cells
what is the full reaction equation from CO2 and H2O to hydrogen carbonate ions?
H20 + CO2 ⇌ H2CO3 ⇌ H+ + HCO3-
what is the chloride shift?
HCO3- ions move out of red blood cells into plasma by diffusion
Cl- ions move into rbc to maintain electrical balance of cell
what is the purpose of removing CO2 by converting it into HCO3- ions?
maintains steep diff gradient of CO2 so it diffuses into rbc from respiring cells
What is the role of haemoglobin in carbon dioxide transport in the blood?
acts as a buffer and prevents changes in pH by accepting the H+ ions in a reversible reaction to form haemoglobinic acid
what type of muscle is the heart made of
cardiac
difference between cardiac and skeletal muscle?
cardiac muscle does not fatigue
what supplies the cardiac muscles with the oxygenated blood it needs to keep contracting and relaxing?
coronary arteries
what do the inelastic pericardial muscles do which surround the heart?
help prevent the heard from over-distending with blood
deox blood enters the ……. via the …………
right atrium
vena cava
the muscular walls of the atria are ……….
thin
why do the atrioventricular valves open?
pressure builds up in the atria as blood flows in from the vena cava/pulmonary artery, forcing the tri/bicuspid valve open to allow blood to flow into the ventricles and relieve the mounting pressure
when does the tricuspid valve close?
when the atrium contracts, all the blood is forced into the right ventricle, stretching the ventricle walls.
The tricuspid valve closes as the ventricle starts to contract, preventing the backflow of blood into the right atrium.
what do the tendinous chords in the valves do?
make sure the valves are not inverted by the pressure exerted when the ventricle contracts
when do the semi lunar valves open?
when the right ventricle fully contracts it pushes the deox blood through the semi-lunar valves into the pulmonary artery -> capillary beds of the lungs.
The semilunar valves then close to prevent the backflow of blood to the heart
ox blood enters the ……. via the ……….
left atrium
pulmonary vein
the muscular wall is much thicker on the ……. hand side. why?
left
left side has to produce sufficient force to overcome the resistance of the aorta and arterial systems of the whole body and move the blood under pressure to all the extremities of the body
septum
inner wall separating lhs from rhs and preventing deox blood from mixing with ox blood
what is the cardiac cycle?
the events in a single heartbeat
~0.8 seconds in a human adult
diastole
heart relaxes
- atria and ventricles fill with blood
- volume and pressure of blood in the lungs builds up as heart fills
- pressure in arteries remains at minimum
systole
- atria contract (atrial systole) closely followed by ventricular systole
- pressure inside heart increases dramatically and blood is forced out of the rhs to lungs and lhs to main body
- at end of systole, vol and pressure of blood in lungs is low and pressure in arteries is at max
lub-dub
lub - blood forced against atrioventricular valves (closing them) as ventricles contract.
dub - backflow of blood closes semi-lunar valves in aorta and pulmonary artery as ventricles contract
what is mean that the cardiac muscle is described as myogenic?
it has it’s own intrinsic rhythm at 60 beats per min
-> prevents the body wasting its resources maintaining the basic heart rate
where is the sino-atrial node (SAN)
located and what does it do?
right atrium
causes atria to contract, initiating heartbeat
where is the atrio-ventricular node (AVN) and what does it do?
right atrium
picks up electrical activity from SAN, imposes slight delay, before stimulating bundle of His
what is the bundle of His?
bundle of conducting tissue made up of Purkyne fibres, two branches which penetrate through septum
what prevents the wave of excitation created by the SAN from being passed directly to the ventricles?
a layer of non conducting tissue (around the SAN?)
where do the purkyne fibres take the wave of excitation? what happens when it gets there?
apex
when the excitation reaches the apex, the purkyne fibres spread out through the walls of the ventricle on either side, triggering the contraction of the ventricles
what does the AVN delay and the way the excitation spreads through the SAN ensure?
that the atria stop contracting before the ventricles start
how do you record the electrical activity of the heart?
electrocardiogragh (ECG)
Describe how the action of the heart is initiated and coordinated (4)
T / SAN, creates / initiates / starts / originates, excitation ;
wave (of excitation) spreads over atrial, wall / muscle ; ref to, AVN / U ; atria contract / atrial systole ; contraction is synchronised / AW ; delay at AVN ; (excitation spreads) down septum ;
ref to, bundle of His / Purkyne fibres ;
ventricles contract / ventricular systole, from, apex / bottom ;
