Chapter 14 - Lymphoid Organs

Question 1

Function of the lymphatic system?

Answer 1

• remove foregin material from lymph and blood
• returns fluid from peripheral tissues to blood
• recognizes and destroys or neutralizes non-self molecules

Question 2

What are the components of the lymphatic system?

Answer 2

• lymphatic vessels
• lymphoid nodules
• lymphoid organs

Question 3

Lymphoid nodules

Answer 3

• nonencapsulated lymphatic tissue
• GI, respiratory, urinary, reproductive tracts
• dense, spherical cluster of B lymphocytes w/ germinative centers
• site of B cell proliferation in response to infection
• spleen, tonsils, lymph nodes

Question 4

Lymphoid organs

Answer 4

• flattened, bean shaped
• surrounded by CT capsule w/ trabeculae that partially divide the node
• filters lymph
• very impt. in defense against bacteria, viruses, tumor cells

Question 5

What are the divisions of lymph nodes?

Answer 5

• cortex - has lymphoid nodules with germinative centers
• medulla - cords and sinuses
• lymph enters from convex side, exits at hilus

Question 6

Tumor metastasis

Answer 6

• cells from malignant tumors can enter lymph and get into lymph nodes
• rationale for lymph node biopsy during tumor resection

Question 7

How does the lymphatic system work?

Answer 7

• lymphoid tissues scan lymph and blood for antigens (foreign particles)
• antigens stimulate immune system (B cells) to make antibodies, or trigger T cells to destroy the antigen

Question 8

Antibodies

Answer 8

• proteins that recognize and bind to antigens
• secreted by B cells
• 5 classes - IgG, IgM, IgA, IgD, IgE
• neutralize antigen or cell by binding to it and aggregating
• cover the surface or foriegn cells - tag it for phagocytosis
• activated complement cascade that leads to lysis of foreign cell

Question 9

B cells and T cells

Answer 9

• B cells produced and mature in bone marrow
• T cells mature in thymus, move btwn blood, lymph nodes, and the spleen (AIDS kills T cells)

Question 10

General characteristics of lymphoid tissues

Answer 10

• CT containing high concentrations of various WBCs, primarily lymphocytes
• encapsulated or non
• contain internal meshwork of reticular fibers
• sinusoidal capillaries
• reticular cells - type of fibroblast that supports lymphoid tissues

Question 11

Tonsils

Answer 11

• help protect against infection by microbes entering oral/nasal cavities
• have a partial capsule - nonencapsulated
• 3 sets - pharygeal, palatine, lingual
• lymphoid nodules

Question 12

Tonsilitis

Answer 12

chronic inflammation or infection of the tonsils

Question 13

Thymus

Answer 13

• final site of T cell maturation
• CT capsule
• Divided into lobules
• Hassal’s corpuscles in medulla (aggregation of reticular cells)
• most active from birth to puberty

Question 14

Lobules of thymus

Answer 14

• cortex - immature T cells and T cell precursors
• medulla - reticular cells, mature T cells, Hassal’s corpuscles

Question 15

Spleen

Answer 15

• largest collection of lymph tissue in the body
• contains phagocytic cells that defend against blood-borne antigens
• removal of old or abnormal RBCs
• thin CT capsule with trabeculae

Question 16

Structure of Spleen

Answer 16

• thin CT capsule
• splenic artery and vein enter/exit at hilus
• contains reticular cells and fibers, lymphocytes and other WBCs

Question 17

Red pulp of spleen

Answer 17

• splenic cords and sinuses

Question 18

White pulp of spleen

Answer 18

• lymphoid nodules around small blood vessels, lymphoid follicles are also here

Question 19

Splenectomy

Answer 19

• surgical removal of the spleen, usually after damage (occurs easily due to thin capsule)
• RBC destruction assumed by liver and bone marrow
• higher risk for certain infectious diseases