Morphological, Mechanical and Hydrodynamic Aspects of Diaphragmatic Lymphatics

Abstract

The diaphragmatic lymphatic vascular network has unique anatomical characteristics. Studying the morphology and distribution of the lymphatic network in the mouse diaphragm by fluorescence-immunohistochemistry using LYVE-1 (a lymphatic endothelial marker) revealed LYVE1+ structures on both sides of the diaphragm—both in its the muscular and tendinous portion, but with different vessel density and configurations. On the pleural side, most LYVE1+ configurations are vessel-like with scanty stomata, while the peritoneal side is characterized by abundant LYVE1+ flattened lacy-ladder shaped structures with several stomata-like pores, particularly in the muscular portion. Such a complex, three-dimensional organization is enriched, at the peripheral rim of the muscular diaphragm, with spontaneously contracting lymphatic vessel segments able to prompt contractile waves to adjacent collecting lymphatics. This review aims at describing how the external tissue forces developing in the diaphragm, along with cyclic cardiogenic and respiratory swings, interplay with the spontaneous contraction of lymphatic vessel segments at the peripheral diaphragmatic rim to simultaneously set and modulate lymph flow from the pleural and peritoneal cavities. These details may provide useful in understanding the role of diaphragmatic lymphatics not only in physiological but, more so, in pathophysiological circumstances such as in dialysis, metastasis or infection.

The emerging importance of lymphatics in health and disease: an NIH workshop report

“…Afferent collecting lymphatics drain into lymph nodes where antigens and immune cells are filtered and sampled by lymph node–resident cells ( 23 – 25 ). Fluid from the lymph nodes is drained by efferent lymphatics that drain into successively larger collecting lymphatic channels.…”

Fluid Osmolarity Modulates the Rate of Spontaneous Contraction of Lymphatic Vessels and Lymph Flow by Means of a Cooperation between TRPV and VRAC Channels

“…In pleural and diaphragmatic lymphatics, both extrinsic and intrinsic mechanisms cooperate to ensure proper lymph flow, with the contractions of the skeletal muscle serving as the primary force affecting lymphatic function [24][25][26]. However, lymphatics located at the periphery of the diaphragmatic dome, where mechanical forces are less pronounced and unevenly distributed, exhibit spontaneous contractions and possess a well-organized LM layer within the vessel wall [27,28].…”