[ii] Elasmobranchii

• Lateral gill components:

  1. Interbranchial septum
  2. Primary lamella
  3. Secondary lamella
  4. Gill ray
• Gill structure configurations:

  1. Hemibranch
  2. Possess lamella but only on one side
  3. Half of holobranch
  4. Holobranch
  5. Lamellae on both sides
• Respiratory unit

  • Facing units of primary gill lamella
• Hemibranch

  • Gills possess lamella but only on one side
  • Half of holobranch
• Holobranch

  • Lamellae on both sides
• Opening as a result of the reduction of the first gill slit

  Spiracle
• Holocephali possess the operculum
• Shark respiration - dual pump mechanism

  1. Suction phase
  2. Buccal cavity expands, increasing negative pressure
  3. Water sucked into buccal cavity
  4. Force phase
  5. Contraction of buccal cavity creates pressure
  6. Water is constrained and pushed further to side of pharyngeal cavity