The smallest lymphatic vessels which associate with capillary beds of the cardiovascular system. These are larger than vascular capillaries in diameter, but with thinner walls made of overlapping endothelial cells which allow fluid and proteins to enter, but prevent their escape.
Fluid reabsorption begins in the lymph capillaries that are throughout the body near blood capillaries. Lymph capillaries are small microscopic tubes that collect extracellular fluid. The walls of lymph capillaries comprise loosely joined cells. The overlapping edges of the cells form mini-valves that allow extracellular fluid to pass into the capillary and prevent fluid from flowing back into the tissue. Unlike blood capillaries, lymph capillaries are blind-end tubes that lead away from the tissue.