Exchange surfaces

?

Features of specialised exchange surface:

  • Large surface area to volume ratio - increases rate of exchange
  • Very thin - short diffusion distance and therefore materials cross the exchange surface rapidly
  • Selectively permeable - allow selected materials to cross
  • Movement of the environmental medium - maintain a diffusion gradient
  • A transport system - to ensure the movement of the internal medium

  • Being thin, specialised exchange surfaces are easily damaged and dehydrated.
  • They are therefore often located inside an organism
  • When an exchange surface is located inside the body, the organism needs to have a means of moving the external medium over the surface

Things that need to be interchanged between an organism and its environment:

  • Heat
  • Excretory products
  • Nutrients
  • Respiratory gases

Except for heat, these exchanges can take place in two ways:

  • Passively (no metabolic energy is required) through diffusion and osmosis
  • Actively (metabolic energy required) through active transport

Small intestine -

  • Large SA:VOL - (microvilli-folds) for

Comments

No comments have yet been made