1. 4/16/2017
CH 20 Lymph Node Anatomy
James F. Thompson, Ph.D.

2. 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

3. 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

4. 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

5. 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

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

7. 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!

8. 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

9. 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

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