3.2: Gas exchange Flashcards
What are the five main structures of human gas exchange system?
1) Trachea
2) Bronchi
3) Bronchioles
4) Alveoli
5) Lungs
What does the contraction of external intercostal muscles lead to
Inspiration - Rib cage moves out and air flows in
What does the contraction of internal intercostal muscles lead to
Expiration - Rib cage moves in so air moves out
Describe inhalation (5)
- External intercostal muscles contract pulling rib cage up and out
- Internal intercostal muscles relax
- Diaphragm contracts and moves down
- Thoracic cavity volume increases
- Pressure in lungs lower than atmospheric pressure
- Air moves into lungs down a pressure gradient
Describe exhalation (5)
- External intercostal muscles relax
- Internal intercostal muscles contract pulling rib cage down and in
- Diaphragm relaxes and moves up
- Thoracic cavity volume decreases
- Pressure in lungs greater than. atmospheric pressure
- Air moves out of lungs down pressure gradient
Diffusion of gases in the alveoli
- Deoxygenated blood from pulmonary artery has low O2 concentration compared to air inside alveoli
- O2 from blood diffuses across squamous epithelial membrane and endothelial wall (of capillary) down concentration gradient
- CO2 moves from blood to alveoli as blood has higher concentration of CO2
- Both gases move in opposite directions by simple diffusion
- Blood circulation and air ventilation maintains concentration gradient to ensure gases don’t reach equilibrium
What are the features of the alveolar epithelium for gas exchange?
- One cell thick for a short diffusion distance
- Network of capillaries to maintain a large concentration gradient
- Many alveoli to create a very large surface area
How is the structure of fish gils adapted for gas exchange? ()
- Many lamellae/filaments so there’s a large surface area so more diffusion
- Lamellae are thin for short diffusion distance
- Lamellae have a thin epithelium between water and blood for short diffusion distance
- Lamellae have capillaries to maintain concentration gradient
- Water and blood flow in opposite directions to maintain concentration gradient so water is always next to blood with lower concentration of O2
- Circulation replaced blood saturated with oxygen
- Ventilation replaces water
Explain countercurrent mechanism in fish gills (3)
1) Water and blood flow in opposite directions
2) Blood always passing water with a higher concentration of oxygen
3) Concentration gradient maintained across full gill lamellae
Movement of oxygen through the insect (4)
- Oxygen enters the insect through spiracles and into tracheae
- Spiracles close to minimise water loss
- Oxygen diffuses through tracheae into tracheoles
- Oxygen directly delivered to respiring tissues down concentration gradient
Describe getting oxygen during flight in insects
- Insect respires anaerobically and produces lactate
- This lowers water potential of muscle cells so water passes by osmosis from tracheoles into muscle cells
- This adaptation draws air in to tracheoles closer to muscle cells to reduce diffusion distance when O2 is needed the most
Adaptations of leaf for gas exchange (3)
- Flat so larger surface area to volume ratio
- Many stomata so pores allow air to move in and out of leaf
- Air spaces in leaf so short diffusion distance between mesophyll cells and air
Diffusion of CO2 for photosynthesis (3)
1) Mesophyll cells photosynthesise and reduces the concentration of CO2 in the cells
2) CO2 diffuses from air spaces into cells
3) This reduced the CO2 concentration in air spaces causing CO2 to move into air spaces through the stomata
Diffusion of O2 for photosynthesis (3)
1) Mesophyll cells produces O2 as a product of photosynthesis
2) O2 diffuses into air spaces from cells
3) This increases the concentration of O2 in air spaces causing O2 to move from air spaces to outside leaves through the stomata
Adaptations to reduce water loss in leaves
- Guard cells close the stomata
- Upper and lower surfaces have a waxy cuticle
- Most stomata are on the lower surface
Pulmonary artery ventilation equation
PVR = Tidal volume x Ventilation rate
PVR = dm3min-1
TV = dm3
VR = min-1
Adaptations to limit water loss in terrestrial insects (3)
1)Rigid exoskeleton covered with waterproof cuticle
2) Small surface area to volume ratio to minimise area water is lost
3) Spiracles can open and close to reduce water loss
Structure of tracheal system in insects
- Spiracles - where oxygen and carbon dioxide enter and leave. Attached to trachea
- Trachea - Tube with rings that strengthen tubes to keep them open. Branch intro smaller tubes called tracheoles which extend to tissues to deliver oxygen to respiring cells
Adaptation for efficient diffusion in terrestrial insects (3)
1) Large number of tracheoles for a large surface area
2) Thin tracheoles walls and short distance between spiracles and tracheoles for short diffusion pathway
3) Use of oxygen and production of CO2 sets up a steep diffusion gradient
Adaptations for xerophytic plants (6)
1) Reduced number of stomata - less surface area for water loss
2) Stomata in pits - reduced concentration gradient
3) Hairs to trap water vapour - Reduced concentration gradient
4) Rolled leaves - Traps water to reduce concentration gradient
5) Leaves reduced to spines so less surface area for water loss
6) Thick waxy cuticles to increase diffusion distance
