Transport In Animals & Plants

• 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

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 

• 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

• 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

• 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

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

• 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

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

• 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

• 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 

• 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

• 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

• 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

• 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

• 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

• 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