Gas exchange in humans Flashcards
What are the parts in the human gas exchange system?
Trachea Ribcage Intercostal muscles Bronchus Bronchiole Diaphragm Alveoli
Where does the air go to as it enters through breathing?
Trachea
What does the trachea split into?
2 bronchi
What does the bronchi branch off into?
Bronchioles
What are the two types of intercostal muscles?
External
Internal
What is ventilation?
Process of inspiration (breathing in) and expiration (breathing out)
What happens during inspiration?
External intercostal muscles and diaphragm contract, it flattens
How does the ribcage move during inspiration?
Upwards and outwards
How do the movements of the diaphragm and intercostal muscles affect volume and pressure? How does this affect the movement of air?
Volume increases
Pressure decreases
The air flows down the trachea down a pressure and diffusion gradient to an area of low pressure
Is inspiration an active or a passive process?
Active
What happens during expiration?
External intercostal muscles and diaphragm relax, it domes
How does the ribcage move during expiration?
Downwards and inwards
What happens to the volume and the pressure during expiration?
Volume decreases
Pressure increases
Is expiration passive or active?
Passive
What happens during forced expiration?
The external intercostal muscles relax and the internal intercostal muscles contract which pulls the ribcage further down and in
What are alveoli?
Microscopic air sacs
What surrounds alveoli?
Capillaries
What is the structure of the alveoli?
Single, thin layer of alveolar epithelium cells
What are the walls of capillaries made from?
Capillary endothelium
What protein is in the walls of the alveoli?
Elastin
How does elastin benefit the alveoli?
Helps alveoli return to normal shape after exhaling and inhaling air
What diffuses out of the alveoli?
Oxygen
What are the factors which affect the rate of diffusion?
A thin exchange surface - short diffusion pathway
A large surface area - there’s lots of alveoli, large area for exchange to take place
Concentration gradient
What is there between the alveoli and the capillaries?
A steep concentration gradient of oxygen and carbon dioxide
What are the two layers that the air has to diffuse across in order to get to the capillaries?
Alveolar epithelium
Capillary endothelium
Just before a person starts to exhale, the composition of the air in an alveolus differs the composition of the air in the trachea. Give two ways in which the composition would differ. (1 marks)
1) More CO2
2) More O2 in alveoli
Suggest why blood returning to the heart from the lungs contains some carbon dioxide (2 marks)
- Not all CO2 will diffuse into the lungs
- The concentration gradient will become equal when there is an equal amount of CO2 into the blood and the lungs
Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood (5 marks)
- Alveoli have a large surface area
- Thin alveolar walls
- Cell membrane permeable to gases
- Wide trachea with cartilage rings
- Capillary walls are thin
Describe and explain the mechanism that causes forced expiration. (4 marks)
- external intercostal muscles and diaphragm are relaxed
- Internal intercostal muscles contract
- decreases the volume and increases the pressure
- air is forced out down a pressure gradient, out of the lungs
People who have been fire-breathers for many years often find they cannot breathe out properly. Explain why. (2 marks)
- Thick layers of scar tissue
- Lose elasticity
- Less recoil
Explain how downward movement of the diaphragm leads to air entering the lungs (2 marks)
- Increases the volume
- Decreases the pressure
- Air moves in down pressure gradient
