# 79 Gaseous exchange
Gas exchange usually involves 2 or more gases transferred in opposite directions across a respiratory surface.
To be efficient, this surface must be:
- thin – shorter distance to diffuse
- moist – allow gases to dissolve
- large surface area
- have a concentration gradient across surface – maintained by movement of air and transport/ use of gas.
- thin – shorter distance to diffuse
- moist – allow gases to dissolve
- large surface area
- have a concentration gradient across surface – maintained by movement of air and transport/ use of gas.
The role of mucus and cilia
- Inside the nose, thin turbinal bones are covered with a layer of cells. Some of which are goblet cells.
- Goblet cells produce a liquid (water + mucus) ---> evaporate ---> moisten nose.
- Cilia: tiny hair-like projections; constantly moving
- Bacteria + dust particles are trapped by cilia and mucus as to not move further inside the gas exchange system.
- Inside the nose, thin turbinal bones are covered with a layer of cells. Some of which are goblet cells.
- Goblet cells produce a liquid (water + mucus) ---> evaporate ---> moisten nose.
- Cilia: tiny hair-like projections; constantly moving
- Bacteria + dust particles are trapped by cilia and mucus as to not move further inside the gas exchange system.
Effects of tobacco smoke on the respiratory system
Tobacco smoke is made up of 4 main toxic chemicals: carbon monoxide, nicotine, smoke particles and tar.
Carbon monoxide:
- combines with haemoglobin in RBC ---> prevents them transporting O2.
Nicotine:
- addictive ---> continual smoking
Smoke particles:
- irritate air passages ---> inflammation + increase mucus production ---> chronic bronchitis.
- presence of smoke particles in alveoli + coughing = emphysema (breathlessness)
Tar:
- a carcinogen: increase risk of lung cancer ( cell division out of control)
- lines air passages:
- increase mucus production
- paralysing + damaging cilia
---> bronchitis
The composition of inspired and expired air
* inspired air: air we breath in
* expired air: air we breath out
- combines with haemoglobin in RBC ---> prevents them transporting O2.
Nicotine:
- addictive ---> continual smoking
Smoke particles:
- irritate air passages ---> inflammation + increase mucus production ---> chronic bronchitis.
- presence of smoke particles in alveoli + coughing = emphysema (breathlessness)
Tar:
- a carcinogen: increase risk of lung cancer ( cell division out of control)
- lines air passages:
- increase mucus production
- paralysing + damaging cilia
---> bronchitis
The composition of inspired and expired air
* inspired air: air we breath in
* expired air: air we breath out
Effects of physical activity on breathing
* tidal volume: amount of air during normal, relaxed breathing
vital capacity; maximum amount of air breathed in or out in one breath
During normal breathing:
- depth (tidal volume) : ≈ 0.5ℓ
- rate: 12 breaths/ minute
During exercise:
- depth: ≈ 5ℓ (depending on age, sex, size & fitness of person)
- rate: over 20 breaths/ minute
The total lung volume is greater than vital capacity (some air always remains in the lungs). If not, alveoli walls would stick together, the lung would collapse.
* tidal volume: amount of air during normal, relaxed breathing
vital capacity; maximum amount of air breathed in or out in one breath
During normal breathing:
- depth (tidal volume) : ≈ 0.5ℓ
- rate: 12 breaths/ minute
During exercise:
- depth: ≈ 5ℓ (depending on age, sex, size & fitness of person)
- rate: over 20 breaths/ minute
The total lung volume is greater than vital capacity (some air always remains in the lungs). If not, alveoli walls would stick together, the lung would collapse.
Video: Gas exchange
Video: Functions of Cilia and Goblet Cells