Microscopic Lymphangiography

Abstract

Like the blood capillaries, the lymphatic microvessels are formed by a thin layer of endothelial cells resting on a delicate basal membrane. This structure, particularly at the initial segment, is widely fenestrated. The cells are anchored to filaments which, as interstitial pressure increases, are believed to open the fenestrations and allow the lymph to enter the lymphatic microvessel [1, 2]. The cutaneous microlymphatic circulation is formed by two superficial networks joined by small perpendicular vessels through which the lymph drains from the superficial into the deep network. This deep network is connected by channels that run in a perpendicular direction from the skin downward to the lymphatic precollectors [1–3]. The lymphatic system is currently conceptualized as an integral component of a drainage network originating from the venous end of microcirculation. Together with the venous portion of the capillary circulation and the interstitium, it constitutes a single system that may be defined as a functional microcirculatory unit [2–6]. The venous and the lymphatic systems work together (Fig. 27.1); they are connected by tiny lymphovenous anastomoses that activate when the pressure in the lymphatic system rises [7–9]. Persistent venous stasis will lead to functional overload in the lymphatic system that may result in dynamic insufficiency because the fluid overload exceeds the transport capacity of the lymphatics.