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histology (E1 Woods) > lect 25: Immune and Lymphatic System II > Flashcards

lect 25: Immune and Lymphatic System II Flashcards

1
Q

what type of lymphatics are present in the capsule of the thymus

A

efferent are present, afferent are absent

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2
Q

what does the trabeculae (septa) do

A

divides the thymus into incomplete lobules (delicate CT)

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3
Q

what is the cortex of lobules of the thymus stained with

A

basic dyes such as H&E

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4
Q

what cells are contained in the cortex of the lobules of the thymus

A

epithelial reticular cells & T cells in various differentiation

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5
Q

what secretes thymosin

A

epithelial reticular cells

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6
Q

what is the medulla of the lobules of the thymus specialized to do

A

allow entry channel into blood stream of mature lymphocytes

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7
Q

what are hassall’c corpuscles

A

whorls of highly keratinized medullary epithelial cells

produce cytokine thymic stromal lymphopoietin

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8
Q

what does lymphopoietin do

A

stimulates thymic dendritic cells needed for the maturation of single positive T cells

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9
Q

what are double negative T cells

A

lack CD4 and CD8
enter cortex from blood vessels
proliferate in subscapular area

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10
Q

what are double positive T cells

A

move to outer cortex
confronted with epithelial cells with cell surface MHC I 7 II for clonal selection
have CD4 and CD8

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11
Q

where are single positive T cells and what do they express

A

TCR and either CD4 or CD8 (not both)

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12
Q

where is clonal deletion complete for T cell differentiation

A

medulla

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13
Q

what expresses keratin 18

A

cortical thymic epithelial cells

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14
Q

what expresses keratin 5

A

medullary thymic epithelial cells

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15
Q

what do thymic cortical epithelial cells participate in

A

clonal selection of immunocompetent T cells

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16
Q

what do thymic medullary epithelial cells participate in

A

clonal deletion of autoreactived T cells

17
Q

what does AIRE do

A

promotes the expression of a portfolio of tissue-specific cell proteins by thymic medullary epithelial cells which normally do not express these proteins (permit identification and disposal of auto reactive T cells)

18
Q

what does Foxn1 do

A

essential for differentiation of thymic epithelial cells

19
Q

where is the blood-thymus barrier located

A

thymic cortex

20
Q

what does the blood-thymus barrier prevent

A

prevents antigens in the blood from reaching developing T cells in thymic cortex

21
Q

why is the blood-thymus barrier leaky during fetal life

A

to allow for development of immunologic tolerance to self-antigen

22
Q

what are the blood filtering functions of the spleen

A 
only lymphatic organ specialized to filter blood
stores and removes worn-out RBC
recycles iron
converts hemoglobin to bilirubin
blood formation in the fetus
23
Q

what are the immunologic functions of the spleen

A

screens foreign material in the blood
produces lymphocytes and plasma cells
removal leads to overwhelming bacterial infections in infants, children, and young adults

24
Q

what is the site of clonal expansion of antigen-stimulated lymphocytes

A

white pulp

25
Q

where are T cells founds in the white pulp

A

areas surrounding the central artery near the center of the white pulp (forms the PALS)

26
Q

what are reticular fibers of white pulp associated with

A

fixed macrophages and support splenic pulp

27
Q

what does the marginal zone of the spleen do

A

forms sinusoidal interface between red pulp and white pulp

28
Q

where do lymphocytes first encounter antigens

A

marginal zone

29
Q

where do activated T-helper cells activate B cells

A

marginal zone

30
Q

what is the main function of Red Pulp

A

filter blood

31
Q

what occurs in billroth cords

A

contain various blood cells, plasma cells, and antigen-presenting cells
terminal capillaries open directly into substance of cords (open circulation)
macrophages destroy worn out or defective RBC

32
Q

where do billroth cords come form

A

red pulp parenchyma

33
Q

what is the most important aspect of venous sinusoids

A

storage sites for healthy RBC

34
Q

what is penicillus composed of

A

pulp arteriole, sheathed arteriole, and terminal capillary

35
Q

where does the terminal capillary drain into to

A

intercellular spaces (open system) or venous sinuses (closed system)

36
Q

what are venous sinuses lined with

A

reticuloendothelial cells

37
Q

where do venous sinuses drain into (course)

A

venous sinuses–> drain into pulp veins–> unite with trabecular veins–> forming splenic veins–> exits at hilus

38
Q

what releases immunoglobulins into the blood circulation

A

plasma cells

39
Q

what is the main function of the macrophage sheath

A

remove aged cells and particles from the blood

histology (E1 Woods) (22 decks)

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