Filtration

Filtration

Definition

• Filtration is the process where water flows across a porous membrane, carrying small solutes that can pass through the membrane's pores.

Key Points

Membrane Characteristics

• Size of Channels: Main difference between membranes is pore size.

  • Large pores in renal glomeruli (approximately 70 nm) allow passage of molecules smaller than albumin (approximately 60 kDa).

  • Tight junctions in cells have no aqueous pores; channels are much smaller (3 to 6 Å), permitting the passage of molecules with a molecular weight of only a few hundred daltons.

Locations of Filtration

• Renal Glomeruli: Primary site for blood filtration due to larger pore size allowing significant solute passage.

• Cellular Tight Junctions: Prevents substantial passage of most solutes due to smaller channel sizes.