Gas Exchange

• Trachea

  Flexible airway supported by rings of cartilage to prevent collapse, lined with ciliated epithelial cells and goblet cells
• goblet cells


  produce mucus
• cilia


  move mucus up to throat
• Bronchi


  2 divisions of trachea
• Bronchioles


  subdivisions of bronchi, muscle walls control flow of air into and out of the alveoli
• Alveoli


  Air sacs at the end of bronchioles, site of gas exchange
• Adaptions of alveoli

  -many = large SA

  -permeable and single layer of cells= short diffusion distance

  -ventilation and network of capillaries around each alveolus to exchange gases = maintained conc. gradient
• Pulmonary ventilation

  diaphragm contracts/ relaxes, external and internal intercostal muscles relax/contract to force air in and out of lungs
• Inspiration

  Diaphragm contracts

  external intercostal muscles contract

  internal intercostal muscles relax

  =increased volume

  =decreased pressure

  =pressure below average

  =air forced into lungs
• Expiration

  Diaphragm relaxes

  external intercostal muscles relax

  internal intercostal muscles contract

  =decreased volume

  =increased pressure

  =pressure above average

  =air forced out of lungs
• insect tracheal system includes

  spiracles

  trachea

  tracheoles

  tracheal fluid
• insects thick exoskeleton

  made of chitin

  reduces water loss

  impermeable to gases
• Spiracles

  openings in exoskeleton that runs along exoskeleton

  can close to reduce water loss

  delivers O2 to cells
• Insects trachea

  A network of internal tubes lined with chitin that branches off into tracheoles to deliver O2 to respiring cells
• Adaptations of tracheoles

  -1um in diameter to extend between cells = short diffusion distance

  -High number = large SA

  - Thin walls = Short diffusion distance
• Insects exhale

  -decreased trachea volume

  -increased pressure

  -CO2 forced out
• Insects inhale

  - increased tracheal volume

  -decreased pressure

  -O2 pulled in
• Tracheal fluid

  fluid found at the ends of the tracheoles in insects that helps control the surface area available for gas exchange and water loss.
• How do insects increase diffusion of O2 when active?

  Produce lactic acid

  decreases water potential in cells

  tracheal fluid moves into cells

  increased surface area in tracheoles

  increased diffusion of O2 for respiration
• Xerophytes


  plants adapted to live in dry conditions
• Common features of xerophytes

  Thich waxy cuticle

  small leaves for decreased SA and less stomata
• Xerophytes adaptations

  -leaves curl inward = stomata face inward = decreased water loss as water vapour trapped = increased humidity = decreased conc. gradient

  -Hairs on end of leaf = trapped water = increased humidity = decreased conc. gradient

  -Sunken stomata = trapped water vapour = increased humidity = decreased conc. gradient

  - thick cuticle

  - extensive root network
• Operculum

  A protective flap that covers the gills of fishes
• Gill Structure

  - gill arches

  - 2 sets of gill filaments per arch

  - blood vessels that run down gill filaments
• Lamellae


  -on surface of gill

  -network of capillaries covered by a single network of cells

  -site of gas exchange
• Lamella adaptations

  many = large SA

  thin = small diffusion distance

  network of capillaries = maintain conc. gradient
• Counter current flow


  water and blood flow in opposite direction which maintains concentration gradient and doesn't reach equilibrium, oxygen can diffuse across the whole length of lamellae