Exchange Surfaces and Gaseous Exchange Flashcards
Why is diffusion enough to supply the needs of a single cell organism? (2)
- Large SA:V
- Low metabolic demands
Features of specialised exchange surfaces in large multicellular organisms? (4)
- Increased surface area
- Thin layers - lower diffusion pathway
- Good blood supply - higher gradient
- Ventilation - higher diffusion gradient
Why do humans need a gaseous exchange system? (5)
- Small SA:V
- Very large volume of cells
- High metabolic rate
- Needs a lot of oxygen for respiration
- Needs to remove carbon dioxide
Features of the nasal cavity? (4)
- Large surface area
- Good blood supply (keeps it warm)
- Hairy lining which secretes mucus (trap dust and bacteria to protect lung tissue from irritation and infection)
- Moist surfaces - increase humidity (reduce evaporation from exchange system)
Features of the trachea? (3)
- Wide tube
- Supported by incomplete rings of strong, flexible cartilage
- Lined with ciliated epithelium with goblet cells (mucus)
Why are the rings of cartilage incomplete in the trachea?
So that food can move easily down the oesophagus behind the trachea
How to ciliated epithelium and goblet cells work together?
- Goblet cells secrete mucus on to the lining of the trachea to trap dust and microorganisms that have escaped the nose lining
- Cilia beat to move the mucus (with dust and microorganisms) out of the lungs
Features of the bronchus? (2)
- Trachea splits off into left and right bronchus
- Supporting rings of cartilage (smaller than trachea)
Features of the bronchioles? (4)
- Bronchi divide to from these
- No cartilage rings
- Walls contain smooth muscle
- Lined with a thin layer of flattened epithelium
Features of alveoli? (3)
- Tiny air sacs (where gas exchange takes place)
- Unique to mammals
- Layer of thin flattened epithelial cells with some collagen and elastic fibres
Explain elastic recoil of the lungs. (2)
- Elastic tissue allows alveoli to stretch as air is drawn in
- When alveoli return to resting size, helps squeeze the air out
Adaptations of alveoli?
- Large surface area (for gas exchange) (SA:V)
- Thin layers (reduce diffusion pathway)
- Good blood supply (maintains steep conc. gradient)
- God ventilation (maintains steep conc. gradient)
What is inspiration? (6)
- Active (energy-using) process
- Diaphragm contracts, flattening and lowering
- External intercostal muscles contract, moving ribs upward and outward
- Volume of thorax increases, pressure in thorax reduces
- Pressure inside is lower than atmospheric air
- Air is drawn in
What is expiration? (6)
- Passive process but can do actively
- Diaphragm relaxes, rests in dome shape
- External intercostal muscles relax, moving ribs down and inwards
- Elastic fibres in alveoli return to normal length
- Pressure in thorax greater than atmospheric air
- Air moves out
How can you measure lung capacity? (3)
- Peak flow meter
- Vitalograph
- Spirometer
What is tidal volume?
The volume of air that moves into and out of the lungs with each resting breath
What is vital capacity?
The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath
What is inspiratory reserve volume?
The maximum volume of air you can breathe in over and above a normal inhalation
What is expiratory reserve volume?
The extra amount of air that you can force out of your lungs over and above the normal tidal volume of air you breathe out
What is residual volume?
The volume of air that is left in your lungs when you have exhaled as hard as possible
- Cannot be measured directly
What is total lung capacity?
The sum of the vital capacity and the residual volume
What is breathing rate?
Number of breaths per minute
How to calculate ventilation rate?
tidal volume x breathing rate (per min)
When does tidal volume change?
When oxygen demands in the body increase.
- Can increase from 15% to 50%
