Which of the following is NOT a capillary transport mechanism?

movement through intracellular clefts or fenestrations

diffusion through the membrane

bulk flow

transport via vesicles or caveolae

Bulk flow

Explanation:

Generally when there is mass movements of molecules of the fluids from a high pressure gradients to low pressure gradients; that is down the concentration gradients, the process is called Bulk flow. In relation to cells, it is the exchange of material between cells through the pores of the adjoining cells. In xylem, water and minerals flow from high pressure roots to the leaves, and phloem transport food substances from the leaves the sources at high pressure to other parts of the plants.

The capillary transport mechanisms involves the movements of fluids, ions across the fenestration of the capillaries due to the hydostatic pressure of the fluid from the high pressure to the low pressure cellular environments. This is common in the glomerulus of the kidney, intestine, and some endocrine glands.

The single wall endothelial lining of capillaries forms continuous wall which allows passage of ions and fluids while restricting movements of large molecules. Generally the high pressure from the hydrostatic pressure forces these materials across the walls.

Simple diffusion which follows concentration gradient across membranes ensures distribution of substances across the walls for fast uptake by the cells.

The movement of Macromolecules across capillary wall is called vesicular transport.

Thus Bulk flow is odd.