Lymphatic vessels drain interstitial fluid (lymph) from tissues and organs, carry it to lymph nodes where it’s filtered, and eventually join the thoracic duct and right lymphatic duct that empty into the venous system. Unlike the blood vasculature that has the heart to pump blood through the vessels, lymph is moved through lymphatic vessels primarily by the movement of surrounding organs and tissues.

• Examine lymphatic vessels in the images to the right (asterisks mark the lumens) and in these three slides (sample 1, sample 2, sample 3). Sometimes lymph will be present in the lumens, which along with the very thin endothelium, is a distinctive, identifying feature of lymphatic vessels.
• In this specimen of liver, examine the portal areas (seen in the image at the right). Portal areas contain arterioles, veins, bile ducts, and lymphatic vessels, providing an excellent opportunity to compare these structures. Asterisks mark the lumens of the lymphatic vessels.

Now, try this short quiz to practice what you’ve learned.

Now for the respiratory system.