ACOLS Manual Lymph Drainage (MLD) Training Practice Test 2026 - Free MLD Practice Questions and Study Guide

Contracting the precapillary sphincter at the entrance to a capillary bed raises resistance to flow into that bed. This means less blood enters the capillaries, so the capillary bed’s volume drops and the capillary hydrostatic pressure falls. With the capillary hydrostatic pressure reduced, the driving force for filtration into the interstitial space also decreases. In short, fewer fluids move into the capillaries, the capillary pressure and volume decline, and filtration diminishes. All of these outcomes occur when the sphincter contracts, so the answer reflects that comprehensive effect.