Review Note

Lymphatic Vessels

■ Serve as one-way drainage toward the heart and return lymph to the bloodstream through the
thoracic duct (the largest lymphatic vessel) or the right lymphatic duct.
■ Are not usually visible in dissections but are the major route by which cancer metastasizes.
■ Function to absorb large protein molecules and transport them to the bloodstream because the
molecules cannot pass through the walls of the blood capillaries back into the blood.
■ Carry lymphocytes from lymphatic tissues to the bloodstream.
■ Have valves, which are constricted at the sites of valves, showing a beaded appearance.
■ Are absent in the brain, spinal cord, eyeballs, bone marrow, splenic pulp, hyaline cartilage, nails,
and hair.