exchange and transport

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  • Created by: wilby99
  • Created on: 27-02-16 15:34
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  • exchange and transport
    • specialist exchange surfaces
      • In single celled organisms the gases required for life can diffuse directly
        • single celled organisms have a large surface area: volume ratio
      • Three main reasons that multicellular organisms have to have a transport system
        • some cells are deep within the body
        • larger organisms have a larger surface area to volume ratio
        • larger organisms have a faster metabolic rate
      • special features of exchange surfaces
        • Larger surface area: Root hair cells
        • thin/short diffusion pathway: alveoli
        • good blood supply and/or ventilation: alveoli/gills
    • gas exchange in mammals
      • features of a gaseous exchange system
        • goblet cells
        • Cilia
        • elastic fibres
        • smooth muscles
        • Cartilage
      • Distribution of features in the gaseous exchange system
        • In the trahea there are elastic fibres, c-shaped cartilage, smooth muscle and ciliated epithelium
        • In the Bronchioles there is smooth muscle, elastic fibres, ciliated epithelium cells with some goblet cells.
        • In the Alveolus there is elastic fibres and alveolar epithelium
        • In the bronchus there is smooth muscle interspersed by pieces of cartilage, elastic fibres and ciliated epithelial cells that contain goblet cells
    • Ventilation in mammals
      • what is ventilation
        • inspiration: intercostal muscles and diaphragm, rib cage rises, pressure and volume, inspiration is an active process.
        • expiration; Intercostal muscles and diaphragm,rib cage falls, volume and pressure, is a passive process
      • spirometers
        • TIDAL VOLUME is the volume of air in each breath. VITAL CAPACITY is the max. vol of air that can be breathed in or out
        • The total volume of gas in the chamber will decrease over time because the carbon dioxide in the air that is breathed out is absorbed by the soda lime.
          • The oxygen that is eft is also used up in respiration as well so the volume decreases
    • Gas exchange in fish and insects
      • fish
        • structure of the gills
          • Each gill is made of tiny plates called gill filaments/primary lamella (these give a large surface area for diffusion)
          • The primary lamellae are covered in secondary lamella called gill plates which increase surface area and have a supply of capillaries.
        • countercurrent system
          • blood flows through the gills in one direction and the water flows over them in the opposite direction
          • maintains a steep diffusion gradient between the water and the blood
        • ventilation in fish
          • the floor of the buccal cavity is lowered
            • water flows in
              • the floor of the B cavity is raised
                • the operculum open
                  • water flows out, over the gills
      • Insects
        • air moves from spiracles through microscopic tracheae which are used for gas exchange
          • oxygen goes down the concentration gradient toward the cells
            • the tracheae branch off into tracheoles which have thin permeable walls to individual cells
          • carbon dioxide moves down its concentration gradient towards the spirales
        • Insets use rhythmic abdominal muscles to change the volume of their bodies and move air in and out through the spiracles
          • larger insects that fly use the rhythmic pumping of their wings to this effect as well


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