insects

• insects- circulatory system


  -open circulatory system

  -circulation is slow and dependent on body movements

  -don't have lungs or gills
• insects- spiracles 


  -pores in each part of their body

  -can be opened and closed- allow diffusion and prevent water loss

  -spiracles lead to small tubes called tracheae which branch off into tracheoles
• insects- tracheae


  -walls strengthened by polysaccharide chitin

  -thin, permeable walls filled with tissue fluid

  -ends of tracheoles are open to individual cells
• insects- tracheae and gas exchange

  -oxygen diffuses into tracheal fluid then diffuses from fluid into body cells

  -when cells are respiring quickly tracheal fluid can be withdrawn into the body fluid, increasing surface area of tracheal wall exposed to air so more oxygen can be absorbed
• tracheal system- insects

  -small network of tubes called tracheoles that carry oxygen around the body

  -tracheoles branch into cells

  -tracheoles contain tracheal fluid that gases can dissolve into
• tracheal system- when the insect becomes more active

  -tracheal fluid moves further into the tissue

  -this means gas exchange happens closer to the respiring cells

  -diffusion alone doesn't support the insect with enough oxygen so thoracic and abdominal movements can move the gases
• insects- spiracles

  -openings along thorax and abdomen

  -gases diffuse into the spiracles and then into tracheoles

  -gases can also diffuse out of the spiracles
• why insects need a well developed transport system

  -high metabolic rate

  -need a large oxygen supply

  -surface area to volume ratio is usually low

  -need to maintain a high concentration gradient