Exchanging Surfaces

avatar
Created by
Jasmeet Kaur

Cards (7)

  • This page is about how two different parts of the human body are adapted so that substances can diffuse through them most effectively. The first bit is about how gases in the lungs get into and out of the blood. The second is about how digested food gets from the gut to the blood.
  • Lungs

    • Transfer oxygen to the blood
    • Remove waste carbon dioxide from the blood
  • Gas exchange in the lungs
    1. Air sacs (alveoli) where gas exchange takes place
    2. Alveoli have an enormous surface area
    3. Alveoli have a moist lining for dissolving gases
    4. Alveoli have very thin walls
    5. Alveoli have a good blood supply
  • Villi

    • Millions of tiny projections on the inside of the small intestine
    • Increase the surface area for absorption of digested food
    • Have a single layer of surface cells
    • Have a very good blood supply to assist quick absorption
  • Absorption of digested food
    1. Diffusion
    2. Active transport
  • Gas exchange in leaves
    1. Carbon dioxide diffuses into the air spaces within the leaf
    2. Carbon dioxide diffuses into the cells where photosynthesis happens
    3. Oxygen and water vapour diffuse out through the stomata
    4. Size of stomata are controlled by guard cells
    5. Leaf shape increases the exchange surface area
    6. Air spaces inside the leaf increase the exchange surface area
    7. Water vapour evaporates from the cells and escapes by diffusion
  • Gas exchange in fish gills
    1. Water containing oxygen enters the mouth and passes out through the gills
    2. Oxygen diffuses from the water into the blood
    3. Carbon dioxide diffuses from the blood into the water
    4. Gill filaments provide a large surface area
    5. Lamellae on the gill filaments increase the surface area even more
    6. Lamellae have lots of blood capillaries to speed up diffusion
    7. Lamellae have a thin surface layer of cells to minimise diffusion distance
    8. Blood flows through the lamellae in one direction, water flows in the opposite direction to maintain a large concentration gradient