Gaseous Exchange

1. leaves
   1. thin, flat and large Surface Area
      1. shorter diffusion path
   2. lots of Stomata
   3. lots of air spaces in Spongy Mesophyll
2. Diffusion

1. large Surface Area:Volume ratio
2. Diffusion is sufficient due to size
3. thin Cell Surface Membrane
   1. short diffusion pathway

1. Trachae
   1. give large Surface Area
2. lots of Spiracles
   1. short diffusion pathway
3. active insects have muscles to Ventilate Trachae
   1. maintains high Concentration Gradient
4. Diffusion in gas phase - faster

1. Gill Filaments and Lamellae provide massive Surface Area
2. Lamellae
   1. lots of capillaries
   2. thin surface layer
      1. faster Diffusion
3. Counter-Current system
   1. maintains high Concentration Gradient

Anexos:

• Lung Diseases

1. Ventilation
   1. maintains high Concentration Gradient
   2. Inhalation
      1. Ribs UP Muscles DOWN Volume UP Pressure DOWN
         1. Muscles = Diaphragm and External Intercostals contract
   3. Exhalation
      1. Ribs DOWN Muscles UP Volume DOWN Pressure UP
         1. Muscles = Diaphragm and External Intercostals relax
   4. when at rest, Tidal and Passive
   5. when exercising, Internal Intercostals contract too, pulling ribs down further and increasing volume in thorax more; muscles in abdomen wall contract, pushing diaphragm up further, increasing volume exhaled
   6. Pulmonary Ventilation = Tidal Volume x Ventilation Rate
      1. PULMONARY VENTILATION: total vol of air moved into lungs during one minute
      2. TIDAL VOLUME: vol of gas inspired/expired during each unforced ventilation cycle
      3. VENTILATION RATE: number of breaths per minute
2. lots of Alveoli
   1. large surface area
   2. surrounded by Capillaries
      1. maintain conc grad
   3. short partially-permeable diffusion pathway
      1. RBCs compressed against capillary wall
   4. moist surface in which oxygen dissolves to help diffusion