Protein concentration in lymph varies inversely with rate of formation. Rate of filtration varies with the tissue. Lymph flow rate is usually low. It is influenced primarily by the rate of formation. For example, if blood capillary pressure is increased by arterial vasodilation or venous constriction, the flow rate of lymph increased.
Valves prevent retrograde flow.
In the udder, the lymph system nearly all flows through the supramammary lymph nodes . There are usually one or two per side, but sometimes up to 7 nodes. They are about 7 x 5 x 2 cm on average. Frequently there are accessory lymph nodes inside the gland and often there are superficial lymph nodes just beneath skin. Edema is the excess accumulation of fluids in tissue spaces.