Lymphoid II

Question 1

Central lymphoid organs

Answer 1

Thymus and bone marrow

Question 2

Peripheral lymphoid organs

Answer 2

Lymph nodes and spleen (encapsulated), and MALT (unencapsulated). There function is antigen surveillance (the immune system is looking for foreign antigens).

Question 3

PALS

Answer 3

Periarterial lymphatic sheath that wraps around the central artery in the spleen. Location of T cells

Question 4

Circulating lymphocytes

Answer 4

75% T cell, 10% B cell, 15% Natural killer cell

Question 5

Diffuse lymphoid tissue

Answer 5

Tissue located in the lamina propria that contains B lymphocytes, eosinophils and plasma cells that secrete IgA

Question 6

MALT

Answer 6

Mucosal associated lymphatic tissue. Located within unencapsulated peripheral organs and contains most lymphatic tissue.

Question 7

IgA

Answer 7

Secretory immunoglobulin that protects most mucosal epithelium. It is differentiated from plasma cells and contains a secretory component that protects it from degradation of lysosomes as it is released into the lumen.

Question 8

Solidary nodules

Answer 8

Diffuse and naive B lymphocytes that have aggregated into nodules (follicles). They are unencapsulated and have no connective tissue around the outer layer.

Question 9

Aggregated nodules

Answer 9

They are partially encapsulated nodules. They are located in the tonsils, Peyers patches, and vermiform appendix.

Question 10

Peyer’s patches

Answer 10

Aggregated nodules that form in the ileum of the GI tract from loose lymphatic tissue. They aggregate to from primary nodules.

Question 11

Secondary nodules

Answer 11

Activated nodules that are identified by a germinal center and a dense uniform mantle around the outside. The germinal center contains more cytoplasm (plasma cells making immunoglobulins).

Question 12

Primary nodules

Answer 12

Nodules that have not been activated and are completely dense and uniform (no germinal center, cytoplasm)

Question 13

Microfold cells

Answer 13

Cells in Peyer’s patches that directly bind pathogens and then pass it to a macrophage to activate an immune response by B and T lymphocytes.

Question 14

Vermiform appendix

Answer 14

Aggregated nodule that forms the terminal narrowed point of the cecum.

Question 15

McBurney’s point

Answer 15

Point of vermiform appendix that indicates position of the appendix.

Question 16

Thymus

Answer 16

Fully encapsulated central organ that produces thymocytes for antigen surveillance. 95% of self antigen T cells are phagocytized while only 5% of the non-self T cells are released into circulatory system for antigen surveillance. Maturation of the thymocytes occurs in the cortex.

Question 17

Blood-thymus barrier

Answer 17

Prevents formed elements of the blood from coming into contact with thymocytes in the cortex of the lobules. This is an area where you don’t want an immune response to occur.

Question 18

Hassal’s corpuscles

Answer 18

Bundles of epithelial reticular cells in the medulla of the thymus. Distinguishing feature of the thymus that defines it as a component of the immune system. Secretes cytokines.

Question 19

Lymph nodes

Answer 19

Encapsulated node that acts as a filter of the lymphatic fluid and drains the lymphatic tissue back to venous vessels. Contains B cells in cortical nodes and T cells in the paracortex.
- They are also biopsy points for tumor cells.

Question 20

Postcapillary high endothelial venules (HEV)

Answer 20

Venules that get blood to the lymph nodes. They are cuboidal endothelium and located in the paracortex

Question 21

Spleen

Answer 21

Encapsulated organ that acts as a filter of the blood that also plays a role in the immune response.

• Storage of platelets for a blood clot response
• hematopoiesis outside of the bone marrow.

Question 22

White pulp

Answer 22

Leukocyte component of the spleen.

• Nucleated
• Most of the cells are B lymphocytes

Question 23

Red pulp

Answer 23

Erythrocyte component of the spleen. Non-nucleated

Question 24

Periarterial lymphatic sheath

Answer 24

Sheath that wraps around the central artery in the spleen. It contains T cells.

Question 25

Open sinusoids

Answer 25

90% of blood filtration occurs here. They contain slits that allow erythrocytes travel from the sinusoid to the red pulp. Only healthy erythrocytes can squeeze back though the slits in the open sinusoids. The rest are destroyed by macrophages.

Question 26

Germinal center

Answer 26

Responsible for activating the immune cells in the secondary nodule. It contains more cytoplasm for plasma cells to make immunoglobulins