3.1.1 Exchange surfaces Flashcards
Why do multicellular organisms require specialised gas exchange surfaces
Smaller SA:V means the distance that needs to be crossed is larger
Substances cant easily enter the cells as in a single celled organism
How is surface area to volume ratio calculated
surface area / volume
Name 3 features of an efficient gas exchange system
- Large surface area e.g. root hair cells
- Thin/short distance e.g. alveoli
- steep concentration gradient e.g. gills
Describe the trachea and its function in the mammalian gaseous exchange system
- Wide tube supported by c-shaped cartilage to keep air passage open during pressure changes
- Lines by ciliated epithelium cells which move mucus produced by goblet cells towards the throat to be swallowed, preventing lung infections
- Carries air to bronchi
Describe the bronchi and their function in the mammalian gaseous exchange system
- Like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells and goblet cells
- However they are narrower and there are 2 of them (one for each lung)
- Allows passage of air into the bronchioles
Describe the bronchioles and their function in the mammalian gaseous exchange system
- Narrower than bronchi
- Do not need to be kept open by cartilage, therefore mostly have only smooth muscle and elastic fibers so that they can contract and relax easily during ventilation
- Allows passage of air into the alveoli
Describe the alveoli and their function in the mammalian gaseous exchange system
- Mini air sacs, lined with epithelium cells, site of gas exchange
- Walls only one cell thick, covered with a network of capillaries (300 million in each lung) which facilitates gas diffusion
Explain the process of inspiration and the changes that occur throughout the thorax
- External intercostal muscles contract while internal relax, pulling the ribs up and out
- Diaphragm contracts and flattens
- Volume of thorax increases
- Air pressure outside the lungs is therefore higher than the air pressure inside so air moves in to rebalance
Explain the process of expiration and the changes that occur in the thorax
- External intercostal muscles relax while internal contract, bringing the ribs down and in
- Diaphragm relaxes and domes upwards
- Volume of thorax decreases
- Air pressure inside the lungs is therefore higher than the air pressure outside so air moves out to rebalance
Explain how a spirometer works
- Used to measure lung volume
- A person breathes into an airtight chamber which leaves a trace on a graph which shows the volume of the breaths
Define vital capacity
- The maximum volume of air that can be taken in or expelled from the lungs in one breath
- Can be calculated from the spirometer graph by finding maximum amplitude
Define tidal volume
- The volume of air we breath at rest
- Can be calculated from the spirometer graph by finding the amplitude at rest
Define breathing rate
- The number of breaths we take per minute
- Can be calculated from the spirometer graph by counting the number of peaks in 1 minute
Name and describe the 2 main features of a fishs gas transport system
- Gills: located within the body, supported by arches, along with which are multiple projections of gill filaments which are stacked up in piles
- Lamellae: at right angles to the gill filaments, give an increased surface area. Blood and water flow across them in opposite directions (countercurrent exchange system)
Explain the process of gas exchange in fish
- Buccal cavity volume increases to allow water to flow in, reduced to increase pressure
- Water is pumped over the lamellae by the operculum, oxygen diffuses into the bloodstream
- Waste carbon dioxide diffuses into the water and flows back out of the gills
How does the countercurrent exchange system maximise oxygen absorbed by the fish
- Maintains a steep concentration gradient as water is always next to blood of a lower oxygen concentration
- Keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed
Name and describe the 3 main features of an insects gas transport system
- Spiracles: holes on the bodys surface which may be opened or closed by a valve for gas or water exchange
- Tracheae: large tubes extending through all body tissues, supported by rings to prevent collapse
- Tracheoles: smaller branches dividing off the tracheae
Explain the process of gas exchange in insects
- Gases move in and out of the tracheae through the spiracles
- A diffusion gradient allows oxygen to diffuse into the body tissue while waste carbon dioxide diffuses out
- Concentration of muscles in the tracheae allows mass movement of air in and out
