Paracellular transport

Paracellular transport refers to the transfer of substances between cells of an epithelium.

It is in contrast to "transcellular transport", where the substances travel through the cell, passing through both the apical membrane and basolateral membrane.

The distinction is in particular significance in renal physiology. Transcellular transport is more likely to involve energy expenditure than paracellular transport.

Capillaries of Blood Brain Barrier have only transcellular transport, in contrast with normal capillaries which have both transcellular and paracellular transport. This is due to the presence of tight junctions in Blood Brain Barrier.

Structure of paracellular channels
Some claudins form tight junction associated pores that allow paracellular ion transport.