Lymphatic anatomy: microanatomy and physiology

This chapter provides an overview of the lymphatic system with an emphasis on how it relates to lymphatic mapping. Lymphatic vessels were first detailed in ancient Greek writings of Hippocrates and Aristotle in the fourth century BC as “fibers which take a position between blood vessels and nerves and which contain a colorless liquid.”Lymphatics permeate the human body, located in nearly every organ except bone marrow, cartilage, and the cornea. It was thought that the central nervous system lacked lymphatics, until recently in 2015, when Louveau et al. demonstrated lymphatic vessels lining the dura within the brain. The body circulates 8–12 L of lymphatic fluid daily, much of which occurs passively and depends on several factors, including hydrostatic pressure, osmotic pressure, diffusion and convection, and chemotaxis. Afferent lymphatics transport lymphatic fluid into lymph nodes, which enters the medullary sinus – a common site for small metastases.