Exchange Surfaces Flashcards
Why do multicellular organisms require specialised gas exchange surfaces
Smaller surface area to volume ratio
Distance needed to cross is larger
Substance cannot easily enter as in a single called organism
How to calculate surface area to volume ratio
Surface area/volume
Name three features of an efficient gaseous exchange surface
Large surface area e.g. root hair cells
Thin/short distance e.g. alveoli
Steep concentration gradient, maintained by blood supply or ventilation e.g. gills
Describe the trachea and its function in the mammalian gaseous exchange system
Wide air tube supported by C-shaped cartilage to keep the air passage open during pressure changes
Lined by ciliated epithelium cells which move mucus, produced by goblet cells, towards the throat to be swallowed preventing lung infections
Carries air to the bronchi
Describe the bronchi and their function in the mammalian gaseous exchange system
Supported by rings of cartilage and are line by ciliated epithelium cells and goblet cells
However they are narrower and there are two of them, one for each lung
Allow 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, smooth muscle and elastic fibres contract and relax during ventilation
Allow 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 all of which facilitates gas diffusion
Explain the process of inspiration/inhalation and the changes that occur throughout the thorax
External intercostal muscles contract whilst internal relax, pulling the ribs up and out
Diaphragm contracts and flattens
Volume of the 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 (exhalation) and the changes that occur throughout the thorax
External intercostal muscles relax (internal contracts), bringing ribs down and in
Diaphragm relaxes and domes upwards
Volume of the 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
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 the maximum amplitude
Define tidal volume
Volume of air we breathe in and our during each breath at rest. Can be calculated from the spirometer graph by finding the amplitude at rest
Define breathing rate
Number of breaths we take per minute. Can be calculated from the spirometer graph by counting the number of peaks in one minute
Describe the gills
located within the body, supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles
Describe the lamellae in fishs exchange system
At right angles to the gill filaments, give an increased surface area. Blood and water flow across them in opposite directions (countercurrent exchange system)
