Electron microscopy of lymphatics of the porta hepatitis.

The ultrastructure of the lymphatics of the porta hepatitis at the junction with the liver parenchyma has been examined. The lymphatics are composed of endothelium composed of flattened cells containing occasional mitochondria, pinocytotic vesicles and nuclei. The cells are bound by maculae adherentes, zonulae occludentes and desmosome-like structures. There are occasional fibers between endothelium and underlying collagen. Occasional pores closed by diaphragms are present. There is very little basement membrane. There is no definite communication with the spaces of Mall and Disse, but the lymphatic lumens are separated from these areas only by the junctional processes, which may be permeable. Lymphatics are present only in collagenized portal areas and not in the liver parenchyma proper.