Ultrastructure of small intestine submucosal and serosal-muscular lymphatic vessels

Lymphatic vessels of small intestine submucosal and serosal-muscular layers in mice and bats have been studied by electron microscopy and tridimensional reconstruction of thin serial sections. Lymphatic endothelium has a continuous appearance, it lacks fenestrations and pores and it is encircled by a thick connective tissue layer. The endothelial wall shows intraendothelial channels, quite similar to those previously described in the lacteal vessels. The author believes that the above mentioned intraendothelial channels, together with pinocytotic vesicles, play a fundamental role in the transendothelial transport of fluids, proteins and macromolecules. Moreover, intercellular specialized junctional complexes do not appear to take any part in this process.