exchange surfaces

• exchange surfaces

  surfaces over which materials are exchanged from one area to another.
• How are exchange surfaces adapted?

  thin membrane, large surface area, lots of blood vessels, ventilated
• gas exchange in lungs

  - large surface area

  - moist lining for dissolving gases

  - very thin walls

  - good blood supply
• Villi

  Tiny finger-shaped structures that cover the inner surface of the small intestine and provide a large surface area through which digested food is absorbed
• How are villi adapted for absorption?

  -A single layer of surface cells

  -A very good blood supply to assist quick absorption
• What do stomata do?

  Take in carbon dioxide, and release the oxygen produced in photosynthesis
• What do guard cells do?

  control the opening and closing of stomata
• Why is a leaf flattened?

  Increases the area of exchange surface to be more effective
• How do gills work?

  Water enters the fish through its mouth and passes out through the gills, oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water
• How are gills adapted for gas exchange?

  Made up of thin plates called gill filaments which maximise the surface area, these are covered in lamellae which increase the surface area further and the lamellae have lots of blood capillaries to speed up diffusion, they also have a thin layer of cells
• Enough substances can be exchanged across the cell membrane to supply for the volume of the cell