Exchange surfaces Flashcards
Why do multicellular organisms require speacalised gas exchange surfaces?
Their smaller SA:V ratio means the distance needing to be crossed is larger and substances can’t easily enter the cells as in a single-celled organism
How is SA to V ratio calculated?
surface area ÷ volume
Name 3 features of an efficient gas exchange system?
- large surface area
- thin/short diffusion pathway
- steep concentration gradient (good blood supply)
Describe the structure trachea?
- wide tube supported by c shaped cartilage to keep air passage open during pressure change
- lined by ciliated epithelium cells moving mucus created by goblet cells towards the throat
What is the function of the trachea?
carries air to bronchi
Describe the structure of the bronchi?
- supported by rings of cartilage
- lined by ciliated epithelium cells and goblet cells
- narrower than trachea and branch of into 2
Describe then function of the bronchi?
allow passage of air into the bronchioles
Describe the structure of the bronchioles?
- narrower than bronchi
- mostly made up of smooth muscle and elastic fibres (can contract and relax during ventilation)
Describe the function of bronchioles?
allow passage of air into alveoli
Describe the structure of the alveoli?
- mini air sacs lined with epithelium cells (site of gas exchange)
- 1 cell thick walls covered with a capillary network
Describe the function of the alveoli?
facilitate gas exchange
Explain the process of inspiration in the lungs?
- external intercostal muscles contract (internal relax)
- the ribs are pulled up and out
- diaphragm contracts and flattens
- volume of the thorax increases and pressure decreases
- air pressure outside the lungs is higher meaning air moves into the lungs
Explain the process of expiration in the lungs?
- internal intercostal muscles contract (external relax)
- the ribs move down and in
- diaphragm relaxes and domes
- volume of the thorax decreases (pressure increases)
- air pressure inside the lungs is higher meaning air moves out the lungs
Explain how a spirometer works?
Measures lung volume when a person breathes into a air tight chamber leaving 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 breathe
Define tidal volume?
Volume of air we breathe in and out during each breathe
Define breathing rate?
Number of breathes taking per minute
How can vital capacity, tidal volume and breathing rate be calculated by using a spirometer?
vital capacity = calculated by finding the maximum amplitude
tidal volume = by finding the amplitude at rest
breathing rate = counting the number of peaks in 1 minute
Describe the gills in the fish’s gas transport system?
supported by arches along which are multiple projections of gill filaments (stacked up in piles)
Describe the lamelle in the fish’s gas transport system?
- at a right angle to the gill filaments
- increase surface area
- blood and water flow across them in opposite directions (countercurrent)
Explain the process of gas exchange in fish?
- buccal cavity volume increases enabling water to flow in (reduced to increase pressure)
- water is pumped over the lamellae by the operculum (O2 diffuses into the blood stream)
- waste CO2 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 conc gradient as water is always next to blood of a lower O2 conc
- keeps diffusion rate constant enabling oxygen absorbtion
Name and describe three main features of an insects gas transport system?
spiracles = holes on body’s surface that may be opened or closed by a valve for gas and water exchange
tracheae = large tubes extending through all body’s tissues supported by rings to prevent collapsing
tracheoles = smaller branches dividing off the trachea
Explain the process of gas exchange in insects?
- gases move in and out of the trachea through spiracles
- diffusion gradient allows 02 to diffuse into the body tissue while CO2 diffuses out
- contraction of muscles in the trachea allows mass movement of air in and out
