Transport in fish and insects

• What are some features of gas exchange in insects?

  -Rings of chitin - only in trachea

  A) rings of chitin

  B) TRACHEOLES

  C) AIR SAC

  D) MUSCLE CELL

  E) TRACHEA

  F) EXOSKELETON

  G) SPIRACLE

  
• What is the exoskeleton and how does it effect gas exchange?

  • Its the outerbody surface
  • Its impermeable so certain gases cant get through
• What are the two main reasons insects need efficient systems for gas exchange?

  • To deliver oxygen to cells - allows aerobic respiration to occur to release energy for cellular processes
  • To remove carbon dioxide from cells
• What are two ways insect gas exchange systems have adapted to balance two conflicting needs?

  • Maximizing gas exchange efficiency
  • Minimising water loss
• What are some adaptations of the trachea?

  • Reinforced with spirals of chitin - this prevents collapsing
  • Multiple trachea - this increases the surface area
• What are some adaptations of tracheoles?

  • Penetrate directly into tissues - this reduces gas diffusion distance
  • Thin walls - reduces gas diffusion distance
  • Highly branched - maximises surface area
  • Not reinforced with chitin - allows gas exchange to occur
  • Fluid at the end of tracheoles - allows oxygen to dissolve to aid diffusion and reduce water loss
• What are the stages of gas exchange in insects?

  • Air enters the tracheal system through open spiracles
  • Air moves into larger tracheae and diffuses into smaller tracheoles
  • Tracheoles branch throughout the body, transporting air directly to cells
  • Oxygen dissolves in water in tracheal fluid and diffuses down its concentration gradient from tracheoles into body cells
  • Carbon dioxide diffuses down its concentration gradient out of the body cells into tracheoles
  • Air is then carried back to the spiracles via the tracheae and released from the body
• How is the concentration gradient between the tissues and air in the tracheal system?

  • Cells using up for respiration
  • Cells producing carbon dioxide in respiration
  • Continuous ventilation - fresh air is supplied to tracheal system
• What are some examples of other ventilation techniques?

  • More spiracles open - allows more oxygen to enter the tracheal system
  • Mechanical active ventilation - muscles around the trachea contract and relax changing the volume and pressure in the abdomen and squeezing the trachea to pump air in and out of the spiracle
  • Movement of tracheal fluid out into tissues
  • Movement of wind muscles connected to sacs - pump air to ventilate the tracheal system
• How can lactic acid accumulation effect the rate of gas exchange?

  • Lactic acid accumulation reduces the water potential in tracheal fluid at the end of tracheoles
  • Water leaves the tracheoles via osmosis
  • A higher surface area is exposed for gas exchange
• What are some challenges for fish?

  • Water is denser and more viscous than air, resulting in slower diffusion for oxygen
  • Water has less oxygen than air
  • Bony fish are very active so have high oxygen demands
• What are the structure of the gills?

  • Gills are covered by an operculum flap
  • Gills consist of stacked filaments containing gill lamellae
  • Gill lamellae are surrounded by extensive blood vessels
• What are some adaptations of gills which makes them efficient for gas exchange?

  • The lamellae provide a large surface area
  • The lamellae membranes are thin to minimise diffusion distance
  • The gills have a rich blood supply to maintain steep diffusion gradients
  • The countercurrent flow of blood and water creates even steeper concentration gradients
  • Overlapping filament tips increase resistance, slowing water flow over gills and allowing more time for gas exchange
• What happens at the countercurrent flow?

  • Blood and water flow over the lamellae in opposite directions
  • This means that that oxygen-rich blood meets water that is at its most oxygen rich when it moves across the gills
  • Oxygen-poor blood returning from the body tissues meets oxygen-reduced water that has had most of its oxygen removed, still allowing diffusion of oxygen into the blood
  • This maintains a steep concentration gradient across the entire gill
• Why is parallel flow less efficient than countercurrent flow?

  • As parallel flow reduces the concentration gradient so less oxygen can be absorbed
• What are the stages of ventilation in the buccal cavity?

  • When a fish opens its mouth it increases the volume of the buccal cavity
  • This decreases the pressure which pulls water into the buccal cavity
  • Water flows over the gills
  • Water flows out through the operculum
  • This drives unidirectional water flow for ventilation providing freshly oxygenated water and removing carbon dioxide