What feature of lymphatic capillaries increases their permeability?

The feature of lymphatic capillaries that increases their permeability is the presence of mini-valves. These unique structures facilitate the entry of larger molecules and even cells into the lymphatic vessels. The mini-valves are formed by overlapping endothelial cells that create flap-like projections. When interstitial fluid pressure rises, these mini-valves open to allow fluid, proteins, and other substances to enter the lymphatic capillaries. Conversely, if the pressure in the capillary lumen rises, the mini-valves close, which prevents the backflow of lymph.

This functionality is crucial for the lymphatic system, as it enables the collection of excess interstitial fluid, waste products, pathogens, and cellular debris from tissues, thereby playing a vital role in immune function and maintaining fluid homeostasis in the body.