B3.1 Gas Exchange Flashcards
Give an example of gas exchange in plants:
Redwood trees absorb CO2 for use in photosynthesis and release O2 in the process.
Give an example of an organ/organ system that provide a specialized surface area for gas exchange in both animals and plants:
- Alveoli in human lungs
- Spongy Mesophyll in Leaves
What is a gas exchange surface in mammals and aquatic organisms?
- Where cells are exposed to air in the lungs.
- Where cells are exposed to water in the gills of a fish.
What properties of a gas exchange surface ensure that exchange is rapid?
- Permeability to O2
- Large surface area in relation to organism
- Moist surface for dissolving substances
- Thin for short distance diffusion
What’s an example of a process used by large multicellular organisms to maintain concentration gradients?
Pumping
Which structure pumps blood close to gas exchange surfaces?
Dense capillary networks
Blood arriving at the gas exchange surface from the dense capillaries has a.…. O2 concentration and a.…. CO2 concentration.
Low, High, respectively.
How do fish maintain high enough concentrations of oxegyn and low enough concentrations of CO2?
They pump fresh water over their gills and then put through the gill slits. The blood flow moves opposite to this process.
What’s the airway path that air travels through?
Nose/Mouth, trachea, bronchi, broncioles.
How does the thorax create pressure changes during ventilation?
Muscle contractions in:
- The diaphragm
- Muscle in the front wall of the abdomen.
- Antagonistic external and internal intercostal muscles between the ribs.
Outline the changes in pressure and shape during inspiration:
1) External Intercostal muscles contract, diaphragm contracts and becomes flatter (moving down).
2) Rib cage moves up and out, thorax volume increases.
3) Pressure drops below atmospheric pressure.
4) Air flows inside with concentration gradient until pressure rises to atmospheric pressure.
Outline the changes in structure and pressure during expiration:
- Internal intercostal muscles contract, abdominal muscles contract and push diaphragm upwards.
- Volume of thorax decreases, pressure rises to atmospheric pressure.
- Air flows out until pressure drops below atmospheric pressure.
Lung gas exchange adaptations (1):
- Airways for ventilation - branching bronchioles ending in alveolar ducts (pack of 6 or 5 alveoli).
Lung gas exchange adaptations (2):
- About 300 mil 0.2-0.5mm alveoli in a adult lung pair, large quantity that provides surface area 40x larger than human outer surface area.
Lung gas exchange adaptations (3):
- Extensive capillary beds - surface area of basket-like networks of blood capillaries is very large.
Lung gas exchange adaptation (4):
- Short diffusion distance as lung alveolus walls and capillaries are single layers of thin cells, making the distance for O2 and CO2 diffusion less than a micrometre.
Lung gas exchange adaptation (5);
- Surfactant for moist surface, allows O2 to dissolve, and prevents alveolar walls from sticking each other.
What does the ‘ventilation rate’ refer to?
The number of time air is inhaled or exhaled per minute.
Tidal Volume
The amount of fresh air inhaled and stale air exhaled with each ventilation.
Inspiratory reserve volume (IRV)
The amount of air a person can forcefully inhale after a normal tidal exhalation.
Vital Capacity
Amount of air that can be exhaled after a maximum inhalation.
Expiratory Reserve volume (ERV)
The amount of air that can be forcefully exhaled after a normal tidal exhalation.
How is tidal volume measured?
By breathing into the spirometer 3 or more times to the check that the readings are consistent.
How is vital capacity measured?
By breathing in as deeply as possible and forcefully exhaling all air until the lungs are empty.
