Lymphatic capillaries play a crucial role in the lymphatic system, characterized by their unique structure that allows for high permeability. Unlike open-ended structures like straws, lymphatic capillaries are closed-ended. Their endothelial cells overlap to form one-way flaps or valves. This design permits interstitial fluid to enter the capillaries as lymph while preventing the fluid from escaping, effectively addressing the potential issue of leakage.

When considering the mechanisms that allow lymphatic capillaries to function properly, it is essential to understand the role of these overlapping endothelial cells. They create a one-way valve system, which is critical for maintaining fluid balance within the body. This means that when interstitial fluid enters the capillary, the flaps close to prevent backflow, ensuring that lymph remains contained within the capillary system.

In evaluating potential explanations for how lymphatic capillaries prevent fluid escape, it is important to note that the pressure within these capillaries can indeed exceed that of the surrounding tissue. However, the presence of the one-way valves ensures that even under higher pressure, the fluid does not leak out. This distinguishes lymphatic capillaries from other structures that might form tight seals, which would inhibit fluid entry altogether.

In summary, the overlapping endothelial structure of lymphatic capillaries is specifically designed to allow fluid to enter while preventing its escape, functioning effectively through the mechanism of one-way valves. This unique adaptation is vital for the proper functioning of the lymphatic system and maintaining homeostasis within the body.