3.1.1 Exchange Surfaces Flashcards
Diffusion
The net movement of particles from an area of higher conc. to an area of lower conc. down a conc. gradient until equilibrium is reached.
SA:V ratio
As organisms increase in size, SA:V ratio decreases.
Presents challenges for larger organisms in terms of meeting their metabolic demands:
diffusion is too slow
diffusion distance is too great
Core 4 feature of specialised exchange surfaces
Increased surface area (elastic fibres allow expansion):
needed for exchange + overcome limitations of SA:V of larger organisms.
Thin layers: distances that substances have to diffuse are short + faster process + efficient.
Good blood supply: steeper conc. gradient, faster diffusion. Substances constantly delivered to + removed from ES.
Ventilation to maintain diffusion gradient: gases - maintain conc. gradient - more efficient.
Process of inhalation
Anatomy: External intercostal muscles contract - ribcage moves up + out.
Diaphragm contracts - flattens down.
Volume: Increase volume of thoracic cavity.
Pressure: Decrease in pressure in thorax below atmospheric pressure.
Air movement: Air rushes in down a pressure gradient - alveoli inflate.
Process of exhalation
Anatomy: External intercostal muscles relax - ribcage moves down/inwards.
Diaphragm relaxes - moves up to resting dome shape - elastic fibres in alveoli relax.
Volume: Decrease in volume of thoracic cavity.
Pressure: Increase of pressure in thorax greater than atmospheric pressure.
Air movement: Air moves out of lungs + moves down conc. gradient - alveoli deflate.
Exchange System properties
Trachea:
Cartilage rings support - prevents collapsing. Cilia waft mucus - trap microorganisms, pathogens - goblet cells.
Bronchioles:
Smooth muscle - dilate + contract airways. Elastic fibres allow elastic recoil to deal with pressure.
Alveoli: Elastic fibres - surfactant for O2 to easily diffuse. Thin squamous cell walls (short diffusion distance). Capillaries in close contact/good blood supply - steep conc. gradient.
Diaphragm:
Contracts - move ribs up + out - increase vol of thorax. Replaces CO2 with O2 - maintains high conc. gradient.
Forced exhalation
Using energy: Internal intercostal muscles contract - pulls ribs down, hard + fast.
Abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly.
Spirometry
Assesses:
Asthma
Pulmonary fibrosis
COPD
+ Used in sport science testing lung function.
1. Tidal Volume: vol of air that moves in/out of lungs with each resting breath.
2. Inspiratory reserve vol: Max vol of air you can breathe in over + above a normal inhalation.
3. Expiratory reserve vol: Extra vol of air you can force out of your lungs over + above the normal tidal vol of air exhaled.
4. Residual volume: Vol of air left in lungs when exhaling as hard as possible.
5. Vital Capacity: Vol of air that can be breathed in when the strongest exhalation is followed by the deepest possible intake of breath.
6. Total lung capacity: Sum of the vital capacity + residual vol.
Water flow over gills
Gills:
Large SA - good blood supply + thin layers for successful GE.
1. Mouth opens: buccal cavity floor lowers, water moves into buccal cavity - increase in volume (decrease in pressure).
(Same time)
2. Opercular valve shut: Opercular cavity containing gills expands - (pressure lowered in opercular cavity).
3. Buccal cavity floor starts to move up: (increase in pressure) - water moves from buccal cavity over gills.
4. Mouth closes: Operculum opens - opercular cavity sides move in (all increase pressure in operculum cavity) forces water over gills + out operculum.
5. Buccal cavity floor steadily moves up - maintaining flow of water over the gills.
Counter current flow
Blood flows along gill arch along filaments - opposite direction through capillaries to the flow of water.
Conc. of O2 higher in water than blood - fresh blood constantly exposed to water.
Maintain high conc. gradient.
Ventilation in Insects
- Air enters via spiracles.
- O2 travels own conc. gradient to cells.
- CO2 travels down conc. gradient to spiracles.
- Spiracles > trachea > tracheoles > tissue fluid.
Tissue fluid:
O2 diffuses into fluid > carries O2 into cells + tissue fluid - withdrawn into body fluid to increase trachea space exposed to air - more O2 absorbed by cells.
