20.3 Lymph nodes cleanse lymph and house lymphocytes

What are the most important secondary lymphoid organs?

lymph nodes

Where are lymph nodes located?

along lymphatic vessels throughout the body

Are lymph nodes normally visible?

NO, they are usually embedded in connective tissue

What are the three major superficial lymph node clusters?

•cervical

•axillary

•inguinal

Major lymph node clusters?

•CAI

•cervical

•axillary

•inguinal

What are the two major functions of lymph nodes?

•cleanse lymph

•activate immune response

How do lymph nodes cleanse lymph?

macrophages remove microorganisms and debris

Why is lymph cleansing important?

prevent pathogens from reaching the bloodstream

Which blood cells remove pathogens in lymph nodes?

macrophages

How do lymph nodes activate the immune system?

lymphocytes encounter antigens and become activated

Which cells bring antigen to lymph nodes?

dendritic cells

What do dendritic cells do once inside a lymph node?

present antigens to T cells

What happens when T cells encounter antigens?

they become activated and begin an immune response

What shape are most lymph nodes?

bean-shaped

What surrounds a lymph node?

dense fibrous capsule

What are trabeculae?

connective tissue extensions projecting inward from the capsule

Capsule vs Trabeculae?

capsule = outside covering

trabeculae = inside dividers

What forms the internal framework (stroma) of a lymph node?

reticular fibers

Function of the stroma?

supports lymphocytes and immune cells

Which regions is the outer part of the lymph node?

cortex

What is found in the superficial cortex?

lymphoid follicles

What is found inside lymphoid follicles?

germinal centers

What predominates in germinal centers?

dividing B cells

What predominates in the deep cortex?

T cells

Which immune cell is abundant throughout the cortex?

dendritic cells

Which region lies deep within the lymph node?

medulla

What structure makes up the medulla?

medullary cords and medullary sinuses

What lymphocytes are found in the medulla?

both B and T cells

What are lymph sinuses?

large lymphatic channels inside lymph nodes

Name two important lymph sinuses?

•subscapular sinus

•medullary sinus

What spans the lymph sinuses?

reitcular fibers

Which cells sit on reticular fibers in lymph sinuses?

macrophages

Function of macrophages in lymph sinuses?

phagocytize foreign material

Where does lymph enter a lymph node?

through afferent lymphatic vessels

Which side of the lymph node receives afferent vessels?

convex side

What is the first sinus lymph enters?

subscapular sinus

After the subscapular sinus, where does lymph travel?

cortical sinuses

After the cortex, where does lymph travel?

medullary sinuses

Through what structure does lymph leave the node?

hilum

Which vessels carry lymph away?

efferent lymphatic vessels

Trace lymph flow through a lymph node

•subscapular sinus

•cortical sinuses

•medullary sinuses

•hilum

•efferent vessels

Which vessels bring lymph into a node?

afferent vessels

Which vessels carry lymph out?

efferent vessels

Are there more afferent or efferent vessels?

more afferent vessels

Why are there fewer efferent vessels?

to slow lymph flow

Why is slowing lymph flow beneficial?

gives macrophages and lymphocytes time to filter lymph

What is lymphadenopathy?

enlarged, swollen lymph nodes

What causes lymphadenopathy?

infection or immune activity

Why do lymph nodes swell during infection?

large number of pathogens become trapped

What is a bubo?

infected, swollen lymph node

Which famous disease produced buboes?

bubonic plague

How can lymph nodes contribute to cancer spread?

metastasizing cancer cells become trapped inside them

Are cancerous lymph nodes usually painful?

NO

Are infected lymph nodes usually painful?

YES