specialised exchange surfaces

  • Created by: aryan26
  • Created on: 09-04-19 11:26
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  • specialised exchange surfaces
    • why do organisms need an exchange surface?
      • Organisms need to exchange substances with their environment
        • cells need to take in oxygen and glucose for aerobic respiration and metabolic processes
        • and need to excrete waste products like carbon dioxide and urea
      • multi-cellular organisms
        • in single celled organisms the substances can diffuse directly
          • the diffusion is quick because of the short distance
        • in multi-cellular organisms diffusion is too slow because:
          • some cells are deep within the body
          • larger animals have a small SA:V ratio-difficult to exchange enough substances to supply a large volume through a small surface
          • multi-cellular organisms have a higher metabolic rate so they use up oxygen and glucose faster
    • Structures have different functions
      • goblet cells- line airways and secrete mucus
        • mucus traps microorganisms and dust to prevent them from reaching the alveoli
      • cilia- on surface of the airways, they beat the mucus.
        • This moves the mucus upwards away from the alveoli which helps prevent lung infections-
      • elastic fibres- in the walls of the trachea, bronchi, bronchioles and alveoli.
        • Help the process of breathing out, on breathing in the lungs inflate which stretches the fibres, then they recoil which pushes air out when exhaling
      • smooth muscle- in the walls, allows their diameter to be controlled.
        • During exercise the muscle relaxes making the tubes wider= less resistance to airflow
      • rings of cartilage- in the walls of the trachea and bronchi and provide support.
        • Strong but flexible and prevents the trachea collapsing when you breathe in
    • increasing efficiency
      • have a large SA
        • -e.g. root hair cells: each branch of a root will be covered in microscopic hairs-gives the roots a large SA to increase the rate of absorbtion of water and mineral ions
      • they are thin
        • e.g. the alveoli: gas exchange surface in the lungs, made from a single layer of thin flat cells called the alveolar epithelium.
          • O2 diffuses out into the blood and CO2 diffuses in the opposite direction. the thin epithelium helps decrease the diffusion distance which increases the rate
      • have a good blood supply and or ventilation
        • e.g. fish gills: gas exchange surface in fish. O2 and CO2 are exchanged between fish's blood and the surrounding water.
          • contain a large network or capillaries and are well ventilated- fresh water constantly passes over them. helps maintain a concentration grafient of O2
    • In mammals the lungs are exchange organs
      • 1-as you breathe in, air enters the trachea, which splits into two bronchi, each leading to a lung
      • 2-each bronchus branches into smaller tubes called bronchioles-
      • 3- the bronchioles end in small air sacs called alveoli where gases are exchanged
      • 4- the rib cage, intercostal muscles and diaphragm work together to move air in and out
  • In mammals the lungs are exchange organs
    • 1-as you breathe in, air enters the trachea, which splits into two bronchi, each leading to a lung
    • 2-each bronchus branches into smaller tubes called bronchioles-
    • 3- the bronchioles end in small air sacs called alveoli where gases are exchanged
    • 4- the rib cage, intercostal muscles and diaphragm work together to move air in and out
  • Structures have different functions
    • goblet cells- line airways and secrete mucus
      • mucus traps microorganisms and dust to prevent them from reaching the alveoli
    • cilia- on surface of the airways, they beat the mucus.
      • This moves the mucus upwards away from the alveoli which helps prevent lung infections-
    • elastic fibres- in the walls of the trachea, bronchi, bronchioles and alveoli.
      • Help the process of breathing out, on breathing in the lungs inflate which stretches the fibres, then they recoil which pushes air out when exhaling
    • smooth muscle- in the walls, allows their diameter to be controlled.
      • During exercise the muscle relaxes making the tubes wider= less resistance to airflow
    • rings of cartilage- in the walls of the trachea and bronchi and provide support.
      • Strong but flexible and prevents the trachea collapsing when you breathe in

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