3.1.1 - exchange surfaces
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what is an exchange surface
a surface on/inside an organism over which exchange of gases, nutrients and waste can take place
what is a mass transport system
a system by which large quantities of exchanged materials can be moved around the body to the cells that need them
why is simple diffusion not good for multicellular organisms
diffusion pathway is too long + too many substrates get used up as they move to the centre cells
what is metabolic activity
the sum of all the reactions in a cell/body
does a large organism have a big or small SA:V
small
does a small organism have a big or small SA:V
big
what are the features of an efficient gas exchange
large SA:V short diffusion distance good blood supply
what maintains a large SA:V in an exchange surface
• Small alveoli (100-300 micrometres) • small but there are lots that increase the SA of the lungs • surfactant producing cells • surfactant - substance reducing cohesive forces of a liquid (phospholipid) • coats the internal surface of alveoli to reduce cohesive forces between water molecules. These forces may make alveoli collapse - reducing SA
what maintains a short diffusion distance in an exchange surface
• alveolus and capillary walls are 1 cell thick • barrier is only 2 cells thick which is less than 1 micrometre • alveolar walls made of squamous epithelial cells • flattened so thin barrier • capillaries are in close contact with alveolus wall • decreased diffusion distance • capillaries are so narrow that red blood cells are squeezed against the capillary wall • rbcs are very close to the air in the alveoli and have a very short diffusion distance
what maintains a good blood supply distance in an exchange surface
• blood system transports CO2 from tissue to lung • higher conc of CO2 in the blood than alveoli so it can diffuse into the alveoli for exhalation • blood transports O2 from lungs • lower conc of O2 in blood than alveoli so it can diffuse into the blood
what is inhalation
getting air into the lungs
what happens to volume during inhalation
diaphragm flattens / moves down external IM contract internal IM relax ribs move up and out volume inside chest (thorax) increases
what happens to pressure during inhalation
pressure decreases
what happens to the movement of air during inhalation
air rushes into the lungs
what is exhalation
getting air out of the lungs
what happens to volume during exhalation
diaphragm relaxes and moves up external IM relax internal IM contract ribs move down and in volume inside chest (thorax) decreases
what happen to pressure during exhalation
pressure increases
what happens to the movement of air during exhalation
air rushes out of the lungs
why do we say the diaphragm contracts and relaxes
it is made out of muscle
what does a spirometer do
measures lung volume
why does the spirometer have a disposable mouthpiece
prevents infection between patients
why is a noseclip worn when using a spirometer
prevents air entering/escaping through the nose
why does a spirometer have soda-lime
absorbs CO2 so it doesn’t go into the chamber
why does the lid of the spirometer go up and down
happens when you breathe in and out