EXCHANGE SURFACES Flashcards
What are the problems of scale?
- as organisms increase, so does their SA:V
- however SA doesn’t increase as much as its volume
- large organisms need to find ways to increase their SA for gas exchange
How does a large surface area provide a perfect exchange surface?
The larger the area across which a substance can diffuse, the more substances can cross in a given time
How does the exchange surface being thin benefit exchange?
Shorter the distance for a substance to diffuse the less time it takes
How does a diffusion gradient provide a perfect exchange surface?
Concentration of substances must be higher on one side than the other fo diffusion to occur down a concentration gradient
How does protection from drying out lead to a perfect exchange surface?
In terrestrial animals water vapour diffuses out of cells on the surface, if too much water is lost the plasma membrane will lose its structure and the cell will die
What are surfactants?
Reduces surface tension of fluid in lungs and helps to make alveoli more stable, prevents exhalation collapsing alveoli
What is the role of macrophages in the lungs?
Engulf pathogens that are inhaled into the lungs to prevent any diseases/infections from occurring in the lungs
What is the function of cartilage?
C shape rings hold the trachea and bronchi open, yet allows them to expand
What is the function of the smooth muscle?
Contracts to narrow the lumen and force air out
What is the function of elastic fibres?
Recoil of elastic tissue widens airways and forces air out of alveoli
What is the function of goblet cells?
Produces and secretes mucus and surfactants
- which traps dust and pathogens to prevent disease
- surfactants prevent lungs drying out
What is the function of ciliated epithelium cells?
Cilia wafts the mucus
Then it is swallowed and killed by Hcl in stomach
What are the stages for inspiration?
- contraction of external intercostal muscles, causing rib cage to move up and out
- muscles in diaphragm contract
- increases vol in thoracic cavity
- pressure in cavity is lowered, below pressure outside body
- air flows down pressure gradient and into the thorax
What are the stages for expiration?
- intercostal and diaphragm muscles relax
- elastic fibres between alveoli recoil back to normal length
- vol decreases, pressure increases= air forced out
What is the difference between breathing out normally and forced breathing out?
- more air can be forced out by contracting internal intercostal muscles moving diaphragm down
- contraction of abdominal muscles raises diaphragm
Define tidal volume
The volume of air moved in and out of the lungs with each breath when you are at rest
-approx 0.5dm3
Define vital capacity
The largest possible volume of air that can be moved into and out of the lungs in one breath
-approx 5dm3
Define inspiratory reserve volume
How much air can be breather in over and above tidal volume
Define expiratory reserve volume
How much air can be breathed out over and above tidal volume
What is the formula for vital capacity?
Tidal vol + inspiratory reserve vol + expiratory reserve vol
Define residual volume
The volume of air that always remains in the lungs after largest exhalation
-approx 1.5dm3
Define dead space
The air in the bronchioles, bronchi and trachea
No gas exchange between air and the blood
How does the spirometer work?
- person breathes into enclosed air chamber
- as person breathes in, vol inside chamber decreases making float drop down
- vice versa for breathing in
- float attached to a pen which maps movement (attached to a revolving drum)
What are precautions that should be taken when using a spirometer?
- container must be filled with soda lime to absorb carbon dioxide
- medical grade oxygen needs to be present in chamber, especially if used for a long duration
- glen the mouthpiece
What is the function of soda lime in the container?
- absorbs carbon dioxide, so it doesn’t go into the air chamber
- useful to measure the volume of oxygen that has been consumed over a period of time
Define breathing rate
Amount of breaths taken in a minute
Define ventilation rate
-breathing rate x tidal vol
Total vol breathed in or out per minute
How do you calculate oxygen consumption?
- chamber must be filled with oxygen
- soda lime in container
- breathe back out= CO2 in expired air absorbed by soda lime
- total vol going back in chamber is less
- traces go down and down
- over a period of time tells you how much O2 vol has been used
What are examples of adaptions to gills?
- large S= increased area for diffusion
- rich blood supply= maintains a high conc gradient
- thin layers= short diffusion pathway
- tips of adjacent gill filaments overlap= increased resistance to flow of water over the gills, water movements slows to allow more time for diffusion
