Exchange surfaces

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Exchange surfaces

need exchange surfaces for metabolic reactions and to remove waste

smaller organisms have a bigger surface area to volume ratio

single celled- substances can diffuse directly in and out, the diffusion rate is quick as they have high SA:V

multi-cellular- diffusion is too slow because they distance is too far, they have a low SA:V (cant exchange enough), have a high metabolic rate. so they need exchange surfaces 

features of exchange surface

large SA:V to increase effciency EG root hairs cells stick into soil an dare covered in hairs which gives alrge SA:V 

thin layer to improve effiency EG alveoli are only a singular layer of cells 

good blodd supply/ventilation to improve effiency EG alveoli are surrounded by large cappliary network and lungs are ventilated constantly this maintains concentration gradients EG gills contain a large network of capillaries and ventilated as fresh water passes over them.

key features of gaseous exchange system

  goblet cells

line the airways, they secrete mucus. The mucus traps microorganisms and dust particles stopping them reaching the alveoli


on the surface of epithelial cells in airways they beat the mucus to move it towards the throat where it is swallowed, this prevents lung infections

  elastic fibres  

are in walls of trachea, bronchi,bronchiolesand alveoli they help breathing out by on breathing in the fibres are stretched and then the fibres recoil and push the air out

  smooth muscle

in walls of trachea, bronchi and bronchioles allows the diameter to be controlled, during exercise they relax making the tubes wider so there is less revision


rings of cartilage in walls of trachea and bronchi proide support, it strong and flexible and stops the trachea an dbronchi collapsing when you breathe in and the pressure stops




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