ventilation in fish

• 1. Mouth opens, lowering floor of buccal cavity

  2. Volume of buccal cavity increases, decreasing pressure

  3. Water sucked into cavity

  4. Mouth closes, floor of buccal cavity raised

  5. Volume of cavity decreases, pressure increases

  6. Water forced out across gill filaments
• Gill

  • Covered by bony flap called the operculum
  • Increase in pressure forces operculum to open, allowing water to leave
• diagram

  A) floor of buccal cavity lowered

  B) water in

  C) floor of buccal cavity raised

  D) operculum opened

  E) water out