Exchange and Transport systems


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  • Exchange and Transport Systems
    • Gas Exchange in Fish
      • Structure of gills
        • Lamella
          • tiny structures which cover gill filaments
          • increase surface area
          • lots of blood capillaries
            • decrease diffusion distance
              • increase rate of diffusion
          • thin surface layer of cells
            • decrease diffusion distance
              • increase rate of diffusion
        • gill fillaments
          • thin plates
          • increase surface area
            • increase rate of diffusion
      • countercurrent system
        • blood flows in opposite direction to water
        • water with high oxygen concentration flows over blood with a lower oxygen concentration
          • steep concentration gradient maintained
            • maximises rate of diffusion
          • never reaches equilibrium
      • lower concentration of oxygen in water than in air
      • water enters through the mouth
    • Gas Exchange in Plants
      • plants need co2 for photosynthesis
        • produces O2 as a waste gas
      • need O2 for respiration
      • mesophyll is the main layer for gas exchange
        • large surface area
          • increased rate of diffusion
      • gases enter through stomata
        • can open and close to allow gas exchange
        • can close to prevent water loss
        • controlled by guard cells
        • open more during the day
        • sunken pits to trap water vapour
      • hairs on epidermis
        • trap water vapour
      • curled leaves with stomata inside
        • protect from windy conditions
        • prevents water loss
      • waxy cuticle
        • prevents water loss
      • reduced stomata
        • prevents water loss
    • Gas exchange in Insects
      • gas enters though microscopic pores called spiracles
        • spiracles can be closed to prevent water loss
      • oxygen travels down the concentration gradient towards cells
      • move through trachea
      • tracheoles go to individual cells
        • thin
          • decreases diffusion distance
        • permeable walls
          • decreases diffusion distance
      • oxygen diffuses directly into respiring cells
        • high SA:V ratio
      • CO2 diffuses down its own concentration gradient towards spiracles to be released into the atmosphere
      • rhythmic abdominal movements moves air in and out of spiracles
      • waxy waterproof cuticle to prevent water loss
      • hairs cover spiracles
        • reduces evaporation
    • Gas exchange in humans
      • ventilation
        • inspiration
          • external intercostal muscles and diaphragm contract
          • ribcage moves upwards and outwards
          • diaphragm flattens
          • thoracic cavity volume increases
          • lung pressure decreases to below atmospheric pressure
          • air moves down the trachea into the lungs
          • active process8
        • expiration
          • external coastal muscles and diaphragm relax
          • ribcage moves downwards and inwards
          • diaphragm curves upwards
          • thoracic cavity volume decreases
          • air pressure increases to above atmospheric pressure
          • air forced down pressure gradient out of the lungs
          • passive
            • forced expiration is active
      • air enters through the trachea
        • this splits into 2 bronchi
          • these branch into bronchioles
            • bronchioles end in air sacs called alveoli
      • adaptations for efficient gas exchange
        • millions of alveoli
        • surrounded by network of capillaries
        • alveolar epithelium only one cell thick and flattened
        • capillary endothelium only one cell thick
        • alveoli contain elastin
          • helps alveoli recoil
      • O2 diffuses out of alveoli into the blood capillaries
      • CO2 diffuses out of the blood into the alveoli
      • Lung Disease
        • Tuberculosis
          • caused by bacteria
          • immune system walls form around alveoli
            • forms tubercles
              • small, hard lump
          • tidal volume decreases
        • Fibrosis
          • formation of scar tissue in the lungs
          • caused by exposure to asbestos or dust
          • less elastic
            • alveoli can not expand
          • tidal volume decreased
          • FVC reduced
        • asthma
          • airways become inflamed
          • reduced airflow
          • FEV1 decreases
        • Emphysema
          • smoking or long term exposure to air pollution
          • inflammation
          • attracts phagoctyes
            • phagocytes produce an enzyme which breaks down elastic tissue
          • alveoli cannot recoil to expel air
          • destruction of alveolar walls
            • reduces SA
        • tidal volume - volume of air in each breath
        • ventilation rate - breaths per minute
        • FEV - maximum volume of air breathed out in one second
        • FVC - maximum volume of air breathed forcefully out after a really deep breath
    • The circulatory system
      • blood vessels
        • Arteries
          • carry blood from the heart to the body
          • thick muscular walls and elastic tissue
            • allows stretch and recoil as the heart beats
            • helps maintain high pressure
          • folded endothelim
            • increases SA
            • allows stretch
          • Atrioles
            • form networks throughout the body
            • directs blood to different areas of demand
            • control blood flow via muscle contractions
        • Veins
          • thinner muscle walls and little elastic tissue because blood is under lower pressure
          • take blood back to the heart
          • valves to stop blood flowing backwards
          • flow helped via muscle contractions
        • blood capillaries
          • very small
          • exchange of substances such as glucose and oxygen
          • adapted for efficient diffusion
            • walls are one cell thick
            • millions
            • fenestrations
          • Tissue fluid forms in capillary beds
            • high hydrostatic pressure at atriolar end of capillary bed
              • causes small molecules to move out
                • decreases water potential to increase osmotic pressure at the venule end
            • drained via lymphatic system
        • Atrioles
          • form networks throughout the body
          • directs blood to different areas of demand
          • control blood flow via muscle contractions
      • The heart
        • Structure
          • ventricles
            • thicker walls than atrium
              • can contract more powerfully
                • blood pumped around whole body
            • left venticle
              • thicker muscular walls than right ventricle
              • can contract more powerfully
                • blood pumped around whole body
          • atrioventricular valves
            • link atria to ventricles
            • stop blood flow back into the atria when ventricles contract
            • open/close depending on pressure
          • semi lunar valves
            • link ventricles t pulmonary artery and aorta
            • stops blood flowing back into the heart when ventricles contract
            • open/close depending on pressure
          • cords
            • prevent AV valves from being forced upwards into the atria when ventricles contract
        • The cardiac cycle
          • ensures blood is flowing continuously around the body
          • 1, Ventricles relax, atria contracts
            • increases pressure in the chamber
            • blood flows from atria to ventricles
          • 2. Ventricles contract, atria relax
            • higher pressure in the ventricles than atria
            • AV valves forced shut
            • Semi lunar  valves forced open
            • blood forced into aorta and pulmonary artery
          • 3. Ventricles relax, atria relax
            • higher pressure in pulmonary artery and aorta causes semi lunar valves to shut
            • blood returns to the atria via the vena cava and pulmonary vein
          • higher volume of blood, lower pressure
          • cardiac output= stroke volume x heart rate
            • cardiac output is the amount of blood pumped by the heart per minute
            • stroke volume is the volume of blood pumper by each heartbeat
            • heart rate is the number of beats per minute

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