3.1 Exchange Surfaces Flashcards
Why do multicellular organisms require specialised gas exchange surfaces ?
As their SA:V ratio is too small to have gasses exchange through their surfaces.
How is surface area to volume ratio calculated ?
Ratio = Surface area / Volume
Name three features of an effective gas exchange system .
A high SA
A short diffusion distance
A high concentration gradient, maintained by blood flow or ventilation.
Describe the trachea and its function in the mammalian gas exchange system.
A wide tube supported by C-shaped cartilage to keep the air passage open during movement and pressure changes
Lined with ciliated epithelial cells which waft mucus, produced by the goblet cells, towards the throat
Carries air to the bronchi.
Describe the bronchi and their function in the mammalian gas exchange system.
Like the trachea, they are supported by rings of cartilage and are lined with ciliated epithelial and goblet cells
They are narrower than the trachea, and there is one for each lung
They carry air to the bronchioles.
Describe the bronchioles and their function in the mammalian gas exchange system.
Narrower than the bronchi
Don’t need to be supported by cartilage, so are made of smooth muscle and elastic fibres (allows for contracting and relaxing during ventilation)
Allows for the passage of air into the alveoli.
Describe the alveoli and their function in the mammalian gas exchange system.
Small sacs which can fill with air, lined with epithelial cells
The site of gas exchange
The walls of the alveoli are only one cell thick and allow for easy diffusion to the capillaries.
Explain the process of inspiration and the changes that occur throughout the thorax.
External intercostal mussels contract while internal relax, pulling the ribs up and out
Diaphragm contacts
Volume of thorax increases
This means air pressure outside the lungs is higher, forcing air into the lungs
Explain the process of expiration and the changes that occur throughout the thorax.
External intercostal mussels relax while internal contract, bringing the ribs down and in
Diaphragm relaxes
Volume of thorax decreases
This increases the air pressure in the thorax, forcing the air out of the lungs.
Explain how a spirometer works.
Used to measure lung capacity
A person breathes into an airtight chamber
This leaves a trace on a graph which shows the volume of the breaths.
Define vital capacity.
The maximal volume of air that can be taken in or expelled from the lungs in one breath
It can be calculated by finding the maximum amplitude on a spirometer graph.
Define tidal volume.
The volume of air we breathe in and out during each 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 a minute.
Name and describe the main two features/sites of a fish’s gas transport system.
Gills : located within the body, supported by arches, along which there are multiple projections of gill filaments
Lamellae : at right angles to the gill filaments, they give an increased surface area. Blood and water flow over them in opposite directions. This is the countercurrent exchange system.
Explain the process of gas exchange in a fish
The buccal cavity of the fish increases in volume when the mouth opens, this forces in water
When the cavity then decreases in volume, water is forced out of the operculum; this forces water over the gills
Oxygen can then diffuse into the bloodstream and carbon dioxide can diffuse into the water.
