mammalian circulatory system Flashcards
5 reasons why multicellular organisms need transport systems
- multicellular organisms have greater metabolic rates
- SA:V decreases as size increases so greater diffusion distances
- molecules may be made in one place but needed in other specific cells/organs
- food is digested in one organ system but nutrients must be transported to every cell
- waste products of metabolism need to be removed from cells and transported to excretory systems
what type of circulatory system do most mammals have
double closed circulatory system
what are the benefits of a double circulatory system
heart is able to simultaneously pick up oxygen and return oxygenated blood to organs and tissues at high speed + pressures
this is necessary due to the high levels of activity in the body needed to keep temperature at 37C
it also helps with the need to deliver and remove substances from cells rapidly
outline the structure + function of an artery
arteries take high pressure blood away from the heart
from inside to out:
small lumen maintains high pressures
tunica intima - smooth endothelium lining reduces friction for increased blood flow
tunica media - thick layer of smooth muscle and elastic fibres allows walls to stretch + recoil to absorb pressure and push blood along
tunica externa - fibrous layer of connective tissue made of collagen which is tough and can resist high pressures
outline the structure + function of a vein
veins return low pressure blood to the heart
from inside to out:
larger lumen with valves to prevent backflow of low pressure blood and accommodates large volume of blood being transported
tunica intima - smooth endothelium lining reduces friction
tunica media - thin layer of smooth muscle and elastic fibres is sufficient as blood is not at high pressures
tunica externa - fibrous layer of connective tissue made of collagen which is tough and durable
outline the structure + function of a capillary
capillaries allow for the exchange of materials between blood cells and tissues, forms a network through tissues that connect arteries to veins
from inside to out:
lumen has a diameter of 7 micrometers which = diameter of a rbc
made up of 1 layer of smooth endothelium which is 1 cell thick so short diffusion distance for rapid exchange between cells and body tissues, endothelium also has perforations in walls allowing for the seepage of plasma
what type of cells are endothelium made of
squamous epithelial cells
closed circulatory system definition
the transport medium is enclosed in vessels and does not come into contact with the cells of the body
double circulatory system definition
a circulatory system where the blood flows through the heart twice during a complete circuit of the body
pulmonary circulation definition
the part of the circulatory system which carries deoxygenated blood away from the right side of the heart to lungs, returning oxygenated blood to left side of heart
systematic circulation definiton
the part of the circulatory system which carries oxygenated blood away from the left side of the heart to the body and returns deoxygenated blood back to the right side of the heart
what makes double closed circulatory systems very efficient
each circuit passes through only one capillary network, maintaining high blood pressures so fast flow of blood back to the heart is maintained
what are the general features of circulatory systems
- fluid to transport dissolves gases, nutrients and waste
- a pumping mechanism to move fluid
- sometimes vessels to carry around fluid
what is an advantage of a closed circulatory system
they are more efficient
what is a disadvantage of closed circulatory systems
more energy is required to maintain it
what 4 components make up blood + their functions
red blood cells - oxygen and CO2 transport
white blood cells - immunity
platelets - initiate process of blood clotting
plasma - transports dissolved substances
what are platelets
cell fragments
10 examples of substances dissolved in plasma
red blood cells, white blood cells, platelets, glucose, amino acids, plasma proteins, mineral ions, hormones, albumin, fibrinogens
what is albumin and why is it important
a plasma protein found in vertebrates which helps to maintain osmotic pressure
what is fibrinogen and why is it important
a plasma protein which is involved in blood clotting
what are 6 functions of blood
- transport of oxygen and CO2 to and from respiring cells
- transport of hormones
- transport of nitrogenous waste products from cells to excretory organs
- transporting cells and antibodies involved in the immune response
- maintenance of steady body temps
- acts as a buffer to minimise pH changes
what is the function of arterioles
regulate the flow of blood into capillaries
what is the function of venules
regulate the flow of blood from capillaries to veins
what are 3 differences in structure of arteries and arterioles
- arterioles have a higher proportion of smooth muscle than arteries
- arterioles have a lower proportion of elastin in walls compared to arteries
- arterioles have slightly larger lumens
why do arterioles have less elastin in walls than arteries
blood flow isn’t as pulsatile/throbbing
why does blood move slower in arterioles
due to friction with vessel walls
what effect does the slightly larger lumen of arterioles have on blood
reduces the pressure slightly
what is blood flow like in arteries
fast
pulsatile
high pressure
what is blood flow like in capillaries + why
slow - gives a longer time for the exchange of substances
low pressure - prevents them from bursting
what makes up the walls of venules
mostly collagen
what is blood flow like in veins
slow
low pressure
smooth
what are 3 mechanisms in veins to aid flow of blood back to heart
- movement of skeletal muscles contract + relax to push blood through veins as they lie near the surface
- valves prevent backflow
- breathing mechanism causes negative pressure in the thorax which pulls blood towards heart
outline the process of chloride shift
- CO2 from respiring tissues diffuses into red blood cell cytoplasm
- CO2 reacts with water to form carbonic acid H2CO3 in a reaction catalysed by carbonic anhydrase with Zn cofactor - keeps CO2 conc down to maintain conc gradient
- carbonic acid dissociates into H+ and HCO3
- HCO3 - diffuses out of red blood cell and into plasma, creating a charge imbalance
- Cl- ions move into red blood cell to reverse charge imbalance (chloride shift) and H+ ions force O2 out of haemoglobin by binding to it forming haemoglobinic acid
- O2 diffuses out of red blood cells and into respiring tissues
why is carbonic anhydrase + Zn2+ used as a catalyst
ensures fast reaction rate which maintains conc gradient of CO2
how is CO2 transported in blood
5% is dissolved in blood plasma as carbonic acid
20% forms carbaminohaemoglobin, which dissociates back when CO2 conc is low
75% travels in blood as HCO3 -
how do plasma proteins help in transportation of CO2
plasma proteins buffer H+ ions which protects the pH of blood from decreasing and denaturing proteins in blood
what is the equation for CO2 transport in blood plasma
CO2 + H2O <> H2CO3 <> H+ + HCO3 -
tissue fluid definition
a liquid produced from the circulatory system when blood plasma passes out and bathes tissue cells, containing dissolved nutrients or waste molecules
lymph definition
modified tissue fluid collected in the lymph system
3 functions of tissue fluid
- transports substances to tissues and returns waste products of cells back to the circulatory system
- bathes cells which protects them
- allows cells to take up products when needed
4 examples of substances found in tissue fluid
- glucose
- oxygen
- amino acids
- CO2
what is the lymphatic system
system of blind-ended lymph vessels that excess tissue fluid is drained into - now known as lymphatic fluid
outline the the process of tissue fluid formation
- at arteriole end of capillaries hydrostatic pressure is greater than oncotic pressure due to arteries, so fluid is forced out
- this fluid is tissue fluid
- 90% of tissue fluid is reabsorbed at the venule end of the capillary, where hydrostatic pressure is less than oncotic pressure because lots of water has left the blood, so water/fluid moves back in via osmosis
oncotic pressure definition
plasma proteins are hydrophilic and decrease the water potential of plasma, creating a water potential gradient therefore increasing the tendency of water to move into blood - this is oncotic pressure
what are 2 examples of things that don’t leave capillaries when fluid is forced out + why
- red blood cells
- plasma proteins
they are too large to fit through pores in capillaries
what are the functions of lymph nodes
involved in immune response and contains lymphocytes
2 examples of lymphoid organs
- bone marrow
- thymus gland
where B-cells and T-cells differentiate
hydrostatic pressure definition
the pressure created by water in an enclosed system
- created by high pressure in arteries as plasma is aqueous
what happens to hydrostatic pressure from arteriole to venule end of capillaries + why
it decreases
due to increased distance from the heart and branching of arterioles into many capillaries
what happens to oncotic pressure from arteriole to venule end of capillaries + why
it stays the same
plasma proteins which generate the pressure do not fit through pores so cannot leave capillaries
partial pressure of oxygen definition
the amount of O2 in tissues aka pO2
what is partial pressure of oxygen like in lungs + why + what effect does this have
pO2 is high due to ventilation
this means O2 is easily able to associate with haemoglobin so haemoglobin saturation is high here
is haemoglobin saturation proportional to pO2 + why
no
this is because O2 association causes conformational changes which affect the ability of haemoglobin to associate with more O2 molecules
how does haemoglobin saturation change its ability to associate with more O2
- after 1st O2 conformational changes make it easier for haemoglobin to associate with 2nd and 3rd O2 molecules
- the 4th O2 is very difficult to associate with as haemoglobin molecule becomes full
- this is why % Hb O2 saturation - pO2 graphs have a characteristic S-shaped curve
what is the difference between foetal haemoglobin and adult haemoglobin
foetal haemoglobin has a greater affinity for O2
this is necessary as it needs to be able to take O2 directly from mothers haemoglobin
what happens to hydrostatic pressure as blood moves away from the heart
it decreases
this is because blood divides into smaller vessels, which have a larger total cross sectional area
also there is a loss of plasma from capillaries
how many oxygen molecules is 1 haem group capable of binding to
1 O2 molecule
how many oxygen molecules can 1 haemoglobin molecule bind to
1 haemoglobin molecule has 4 haem groups so it can bind to 4 O2 molecules
give the equation for haemoglobin binding to oxygen
Hb + 4O2 <> HbO8
what is formed when haemoglobin binds to O2
oxyhaemoglobin
positive cooperativity
the conformational change of a protein following the binding of the first subunit which then makes binding easier for the next subunits
- seen in haemoglobin
what does an oxygen dissociation curve show
it shows how the binding of O2 molecules varies as different pO2
what is pO2 like in the lungs
very high
what is pO2 like in respiring tissues
low
what does the s shape of an oxygen dissociation curve show
x axis - pO2 (kPa)
y axis - %Hb saturation with O2
for a relatively small change in pO2 there is a large change in %Hb saturated with O2
- this is due to positive cooperativity of Hb
why can the O2 saturation of haemoglobin never be 100%
some Hb will be bound to CO2
what is formed when haemoglobin binds to CO2
carbaminohaemoglobin
what is formed when haemoglobin binds with H+
haemoglobinic acid
what 4 main conditions cause haemoglobin to dissociate from O2
- drop in [O2]
- increase in [CO2]
- increased temperature
- increased blood pH
this causes oxygen dissociation curve to shift to the right
what is the Bohr effect
the phenomenon that Hb oxygen affinity is inversely related to blood pH and [CO2]
the movement of the oxygen dissociation curve to the right under these specific conditions
how does haemoglobin differ in animals that live in environments with low pO2
the haemoglobin has a higher affinity for O2
e.g. a foetus
what effect does a higher affinity for O2 have on the oxygen dissociation curve
the curve shifts to the left
what happens to oxygen dissociation curve at respiring tissues
respiring tissues have high [CO2] so curve shifts to right so more O2 is released from Hb
