Gas Exchange Flashcards
Features of efficient gas exchange
- Large surface area - increases rate of diffusion
- Thin surface - short diffusion pathway
- A good blood supply to maintain a steep gradient
How are fish adapted for gas exchange?
- They have gills with multiple gill filaments which have lamallae
- Blood and water flow in a counter current system. This ensures a steep diffusion gradient so the maximum amount of oxygen is
diffusing into the deoxygenated blood from the water along the whole length of the gill filament
How are insects adapted for gas exchange?
- Air moves into the trachea through the spiracles
- Oxygen travels down the concentration gradient
- Tracheoles have thin, permeable walls
- They use rhythmic abdominal movements to move air in and out
How are plants adapted for gas exchange?
- Leaves have many stomata to allow gases to enter and leave
- Stomata also controls water loss, guard cells swell for them to open
- Short diffusion pathway
- The surface of the mesophyll cells have a large surface area
How can insects and plants control water loss?
- Insects close their spiracles, they also have a waterproof waxy cuticle and tiny hairs to reduce evaporation
- Plants stomata open during the day for gas exchange, Water enters making them turgid. When the plant gets dehydrated, guard cells lose water which closes the stomata
Xerophytic adaptations
- Stomata sunk in pits to trap moist air
- Layer of hairs on epidermis to trap moist air
- Curled leaves which protect the stomata from the wind
- Reduced number of stomata, so fewer places for water to leave
- Waxy, waterproof cuticles to reduce evaporation
Mammalian inspiration
- External intercostal and diaphragm muscles contract
- This causes the ribcage to move up and out and the diaphragm to flatten which increases the volume of the thoracic cavity
- The lung pressure decreases
- Air flows from an area of higher pressure to an area of lower pressure
- Requires energy
Mammalian expiration
- External intercostal and diaphragm muscles relax
- Ribcage moves down and in and the diaphragm curves
- The volume of the thoracic cavity decreased and the air pressure increases
- Passive process
Gas exchange in the alveoli
- Big surface area due to huge number
- It is surrounded by a network of capillaries
- Oxygen diffuses out of alveoli, across alveolar epithelium and capillary endothelium, into the haemoglobin into the blood
- Carbon dioxide moves out into the alveoli and breathed out
How are alveoli adapted?
- Thin exchange surface - one epithelium cell thick, so a short diffusion pathway
- A large surface area
- Constant blood supply due to a large network of capillaries, maintaining a steep concentration gradient between O₂ in the alveoli and O₂ in the blood
Why is there no cartilage at the back of the trachea?
So that the oesophagus is not constricted
What is equipment is used to measure gas exchange in the lungs?
Spirometer
What is tidal volume?
Volume of air in a normal breath
What is ventilation rate?
The number of breaths a person takes per minute
What is forced expiratory volume?
Maximum volume an individual can expire in one second