ch 20 lymph node anatomy james f. thompson, ph.d
TRANSCRIPT
CH 20
Lymph Node Anatomy
James F. Thompson, Ph.D.
The Lymph Nodes•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•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• 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
• 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
follicles withgerminal centers
Histology of Lymph Nodes
Circulation in the Lymph Nodes• 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!
• 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
Lymph Flow Through Lymph Nodes
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