Very large molecules may be too big to diffuse across endothelial cells. In some cases, vesicles contained in the capillary membrane use endocytosis and exocytosis to transport material between blood and the tissues.
Some nutrients are also carried out by 'bulk flow', the flow of 'water' (plasma) caused by a high pressure inside the capillary. Nutrients are carried out through capillary clefts.
The word 'capillary' can also be used to describe any very narrow tube or channel through which a fluid can pass. The adhesive properties of water cause it to rise against gravity within a capillary until the adhesive forces equal the gravitational force on the water column. This phenomenon is known as the capillary effect.