The first step for lymphatic vessels to remove excess fluid from interstitial tissue spaces is by: (A) Generating a lower intravascular than tissue hydrosta tic pressure, (B) Contracting and forcing lymph into larger lymphatics, (C) Opening and closing one-way valves in the lymph vessels, (D) Lowering the colloid osmotic pressure inside the lymph vessel
Answer is A. Although all of the choices are events that happen in lymph vessels, the first key event is lowering the lymphatic hydrostatic pressure to enable tissue fluid to enter the lymphatic vessel.