Answer: The endothelial cells of lymphatic capillaries are tightly connected to prevent interstitial fluid from entering____ back into the interstitial spaces between cells.
Explanation: The interstitial fluid is the one which is found between the cells of any organ within the body. Where does this fluid come from? It leaks out from the thinly lined blood capillaries, as the blood passes through these organs. The lining of the blood capillary is porous enough so that this fluid leaks out into the nearby spaces and only the cellular components of blood, proteins and other large cells stay within the capillaries.
This interstitial fluid is then collected by the lymphatic system and brought back to the blood. So the function of lymphatic system is to collect this fluid back from the interstitial spaces and secure it within it's capillaries so that it reaches straight to the blood stream. Any leakage here would defeat the purpose of the lymphatic system. Hence lymph capillaries have tightly connected cells to prevent this leakage.