[i] Gills

• Gills are primarily used by water breathing vertebrates
• Capillary beds in branchial region are responsible for external respiration
• Provide soft structural support for the gills

  Branchial arches
• Shark gills are covered by an interbranchial septum
• Teleost gills are covered by an operculum or opercular series
• Ventilation types in gills:

  1. Buccal pumping
  2. Ram ventilation
• Expansion and compression of the buccal cavity for ventilation

  Buccal pumping
• Continuous swimming to push water into branchial then opercular cavity

  Ram ventilation
• In external gills, capillary beds scattered throughout the gills to increase likelihood of external respiration