Transport In Animals & Plants

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Features Of Systems

  • suitable medium to carry materials- blood
  • closed system of vessels containing blood forming branching network to distribute
  • pump for moving blood
  • valves for one way flow
  • respiratory pigment increasing volume of oxgen that can be carried
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Open & Closed Systems

insects

  • open blood system
  • blood is at low pressure and pumped from dorsal tube heart running length of the body
  • blood is pumped into haemocoel within the body cavity
  • blood bathes tissues directly
  • little control over circulation direction
  • blood returns slowly to heart where valves and muscles push blood to head region
  • no respiratory pigment as blood doesnt transport oxygen

mammals

  • closed circulation system
  • blood circles in continous loop of blood vessels
  • blood is pumped by heart at high pressure with rapid flow rate
  • organs are not in direct contact but bathed in tissue fluid from capillaries
  • respiratory pigment haemoglobin 
  • earthworm has 5 pseudohearts running length of body along dorsal and ventral vessles 
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Single Circulation

  • closed circulations are of 2 types
  • depends on whether blood passes through the heart once or twice

fish

  • single circulation
  • heart pumps deoxygenated blood to gills
  • oxygenated blood leaves gills and goes to tissues
  • deoxygenated blood returns to heart
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Double Circulation

  • blood passes twice through the heart
  • when blood passes into the lungs pressure is reduced
  • drop in pressure makes circulation slow
  • blood returns to heart to be pumped again at higher pressures for quicker circulation
    • pulmonary circulation- right side of heart pumps deoxygenated blood to lungs, oxygenated returns to left of heart
    • systematic circulation- left side of heart pumps oxygenated blood to tissues, deoxgenated blood returns to right of heart
    • blood passes through the heart twice
  • double circulation is more efficient as higher pressures are generated
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Blood Vessels

  • 3 types: arteries; veins; capillaries
  • same basic 3 layered structure, proportions are different
  • innermost layer is endothelium, one cell thick, smooth lining, reduces friction, medium resistance to blood flow (capillary is just endothelium)
  • middle layer is tunica media, elastic fibres, smooth muscle, thicker in arteries than veins because of blood flow and pressures
  • outer layer is tunica externa; collagen fibres resist over stretching
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Functions

arteries

  • carry blood away from heart
  • thick muscular walls to withstand high pressure 
  • contraction of these muscles maintains pressure 
  • branch into smaller arterioles, then into capillaries

capillaries

  • thin walled single cell thick, permeable to water and dissolved substances
  • exchange of materials are allowed 
  • form vast networks which penetrate all organs and tissues
  • small diameter and friction with wall slows blood flow

Veins

  • collect deoxygenated blood from venules
  • larger diameters and thinner walls reduces pressure and flow
  • semi lunar valves prevent backflow
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Heart

  • thin walled collection chamber
  • thick walled pumping chamber 
  • parted in 2 for separation of deoxygenated and oxygenated bloods
  • 2 separate pumps
  • left = oxygenated
  • right= deoxygenated
  • each has atria and ventricles
  • mainly made of cardiac muscle 
  • myogenic= capable of rhythmic contractions and relaxations of its own accord

valves

  • used to prevent backflow of blood
  • atrio-ventricular valves= bicuspid and tricuspid 
  • semi lunar valves
  • vein valves 
  • all have same design and operate in same way
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Cardiac Cycle

systole= contractions diastole= relaxtations

  • Atrial systole
    • right and left ventricles relax
    • tricuspid and bicuspid valves open
    • atria contract, blood flows into ventricles
  • ventricular systole
    • atria relax
    • ventricles contract together 
    • blood is forced out of pulmonary artery and aorta as semi lunar valves open
    • tricuspid and bicuspid valves close by rise in pressure
    • pulmonary artery= deoxygenated to lungs aorta= oxygenated to body
  • diastole
    • ventricles relax pressure falls
    • high pressure blood in arteries forces semi lunar valves to shut preventing backflow
    •  blood enters from vena cavae and pulmonary veins enters atria and cycle restarts
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Pressure Changes In The Heart

  • highest pressure occurs in the aorta & arteries
  • rhythmic rise and fall consistant with ventricular contraction
  • friction with vessel walls cause drop in pressure
  • arterioles have large surface area but narrow lumen, reducing aortic pressure
  • pressure depends on dilation or contraction
  • extensive capilary networks cover a large cross section meaning greater resistance to blood flow
  • relationship between pressure and speed. pressure drops due to leakage from capilaries to tissues
  • return flow to heart is non rhythmic
  • pressure in veins is low but is increased by massaging effect of muscles
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Heartbeat

  • cardiac muscle is myogenic
  • within wall of RA there are specialised cardiac fibres called  sino-atrial node which acts as a pacemaker
  • electrical stimulation wave arises and spreads across atria causing a contraction
  • electrical stimulation is stopped by layer of connective tissue from spreading to the ventricles
  • this is a layer of insulation
  • stimulation reaches more specialised cardiac fibres the atrio-ventricular node which lies between the atrias and passes the excitation to specialised tissues in the ventricles
  • they pass to the bundle of His to the apex where the bundle branches into purkinje fibres in the ventrical walls
  • this causes the wave of excitation to pass up the walls so the ventricle contracts upwards simultaneously to completely empty the ventricles 
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Blood

  • made of 45% cells in 55% fluid plasma
  • Red blood cells- erythrocytes
    • pigment haemoglobin to transport oxygen
    • biconcave to increase surface area for easier diffusion of oxygen
    • no nucleus for more room for haemoglobin maximising oxygen capacity
  • White blood cells- leucocytes
    • larger, with nucleus and spherical or irregular
    • granulocytes- pphagocytic, granular cytoplasm, lobed nuclei and engulf bacteria
    • agranulocytes- make antibodies and antitoxins, clear cytoplasm and spherical nuclei
  • Plasma
    • 90% water with soluble food molecules, waste products, hormones, plasma proteins, mineral ions and vitamins dissolved in it
    • transports co2, digested food products, hormones, plasma proteins, fibrinogen, antibodies and distributes heat
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Transport Of Oxygen

  • haemoglobin needs to readily associate with oxygen at the lung surface and then readily disassociate at the tissues
  • it can change its affinity for oxygen in the presence of carbon dioxide by changing shape
  • altering its shape releases the oxygen
  • at low concentrations of oxygen haemoglobin finds it difficult to bind with it ut once loaded it readily associates. at high partial pressures of oxygen the % of saturation wth oxygen is high
  • partial pressure is high in the lungs therfore red blood cells load with oxygen, becoming saturated with oxyhaemoglobin
  • until reaching respiring tissues where partial pressure is low and oxygen dissociates
  • a small decrease in partial pressure of oxygen leads to a huge increase in dissociation 
  • the more a dissociation curve is displaced to the left the more readily it picks up oxygen but less readily releases it
  • the more a dissociation curve is displaced to the right the less readily it picks up oxygen but more easily releases it
  • bohr effect: the higher partial pressure of carbon dioxide the more the curve shifts to the right
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Foetal Haemoglobin & Other Animals

  • to enable the foetus to absorb oxygen from the mothers haemoglobin the haemoglobin of the foetus differs in 2 of the four polypeptide chains from the haemoglobin of the adult
  • the structural difference allows the haemoglobin of the foetus to associate more readily with oxygen than the mother, as it has a greater affinity for oxygen
  • dissociation curve shifts to the left

lugworm

  • low metabolic rate lives in sand
  • pumps seawater through its burrow to get access to limited oxygen
  • haemoglobin has a very high affinity for oxygen and dissociation curve to the extreme left

llama

  • lives at increased altitudes where partial pressure of oxygen is low
  • haemoglobin has high affinity for oxygen and dissociation curve to the left
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Myoglobin

  • more stable than haemoglobin
  • wont release oxygen unless partial pressure is extremely low
  • dissociation curve is to extreme left
  • higher percentage saturation than haemoglobin
  • oxygen held acts as reserve used only in conditions of oxygen demand
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Transport Of Carbon Dioxide

  • in solution in the plasma
  • as hydrogen carbonate
  • combined with haemoglobin to form carbamino-haemoglobin
  • some transported in rbc but converted into hydrogen carbonate which then dissolves in plasma
  • chloride shift
    • co2 diffuses into rbc combines with h20 makes carbonic acid (catalysed by carbonic anhydrase)
    • carbonic acid dissociated into H+ and HCO3-. 
    • HCO3- diffuse out of rbc into plasma
    • combine with Na+ = NaHCO3-
    • H+ provides conditions for oxyhaemoglobin to dissociate from oxygen
    • H+ ions buffered by combination with haemoglobin to make haemoglobinic acid 
    • oxygen leaves rbc for tissues
    • chloride diffuses i to balance net movement out of negative ions
    • electrochemical neutrality of rbc is maintained
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Intercellular Fluid

  • capillaries are site of exchange for materials between blood and body
    • thin permeable walls, large surface area, slow bloodflow
  • plasma fluid can escape the walls of capillaries- tissue fluid
  • bathes the cells providing them with nutrients they need and removes waste
  • blood pressure and diffusion are responsible for movement of solutes and water in and out of capillaries
  • when blood reaches arterial end of a capillary it is under pressure from heart and resistance to blood flow creating a hydrostatic pressure to force fluid out of capillary walls and into spaces between cells
  • outward flow is opposed by reduced water potential of blood
  • hydrostatic pressure of blood is greater than osmotic forces so net flow is outward
  • at arterial end diffusion gradient favours movement from capillaries to tissue fluid as these substances in it are being used during cell metabolism
  • at venous end blood pressure is lower and water passes inward by osmosis as reduced water potential causes net inflow
  • venous end tissue fluid picks up waste and CO2, some of it passes back into capillaries some collects into lyphatic system to return to heart later on via thoracic duct
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