4/16/2017 CH 20 Lymph Node Anatomy James F. Thompson, Ph.D.

The Lymph Nodes Anatomy 4/16/2017 Anatomy oval, bean shaped structures scattered throughout body along lymph vessels may be deep or superficial concentrated along the respiratory tree and GI tract, in the mammary glands, axillae, and groin filter lymph fluid to trap foreign organisms, cell debris, and tumor cells

Lymphatic Organs – Lymph Nodes 4/16/2017 Covered by a fibrous connective tissue capsule Trabeculae extend from cortex to medulla Stroma – the internal supportive connective tissue network of reticular fibers

Structure of a Lymph Node 4/16/2017 Structure of a Lymph Node outer cortex - filled with lymph follicles outer edge of follicle contains more T cells inner germinal center is the site of B-cell proliferation inner medulla - medullary cords of lymphocytes, macrophages, plasma cells (activated B cells) Cortex Medulla

Structure of a Lymph Node 4/16/2017 Structure of a Lymph Node Medullary cords extend from the cortex and contain B cells, T cells, and plasma cells Throughout the node are lymph sinuses crisscrossed by reticular fibers Macrophages reside on these fibers where they phagocytize foreign matter

Histology of Lymph Nodes 4/16/2017 follicles with germinal centers

Circulation in the Lymph Nodes 4/16/2017 Lymph enters via a number of afferent lymphatic vessels It then enters a large subcapsular sinus and travels into a number of smaller sinuses It meanders through these sinuses and exits the node at the hilus via efferent vessels The node acts as a “settling tank,” because there are fewer efferent vessels, lymph stagnates somewhat in the node This allows lymphocytes and macrophages time to carry out their protective functions Only lymph nodes filter lymph!

Lymph Flow Through Lymph Nodes 4/16/2017 Lymph Flow Through Lymph Nodes fluid enters cortex through afferent vessels filter and trap damaged cells, microorganisms, foreign substances, tumor cells by reticular fibers macrophages phagocytize some, lymphocytes destroy some by immune defenses exits medulla by efferent vessels at hilus

Blood Flow Through Lymph Nodes 4/16/2017 Blood Flow Through Lymph Nodes blood vessels enter and exit at the hilus this blood circulation provides nutrition for the node’s tissues and a route for leukocytes to enter into or exit from the lymphatic tissue of the node

End CH 20 Lymph Node Anatomy 4/16/2017 End CH 20 Lymph Node Anatomy