Figure 1
Lymph flow pathway. (A) Lymph flow pathway from formation in the interstitial space to return to the subclavian vein (Top) and indicative pressure values at each compartment (Bottom). Subatmospheric pressures have been measured in various interstitial spaces, initial lymphatics and pre-collectors. Previously, it was not known how the lymphatic system pulls in fluid from these spaces and delivers it, against the prevailing hydrostatic pressure gradient, into collecting lymphatics in which luminal pressure is positive, given that these vessels are only capable of contraction (“Problem of interest” as indicated). (B) An isolated, cannulated, and pressurized lymphatic vessel from rat mesentery containing six valves (V1–V6). When cannulated and pressurized at body temperature, these vessels resume their dynamic contractile function without any outside stimulus. Pressure was measured using a servo-null micropipette in either the first or second lymphangion (pressure measurement site, p 1), and diameters were measured by edge detection as indicated by “tracking site.” Inlet and outlet pressures p in and p out were imposed by the heights of the inlet and outlet reservoirs, respectively. The height of the fluid in the bath above the centreline of the vessel resulted in an external pressure p e of 0.5 cmH2O. In the experiments reported here, all lymphangions contracted in an essentially synchronous manner, in that time delays were small enough that intermediate valves always remained open, and a single relaxation phase (thus suction period) was detected along the entire vessel.
