Lecture 32: Lymphoid organs Flashcards Preview

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Flashcards in Lecture 32: Lymphoid organs Deck (26):
1

primary lymphoid organs

bone marrow, thymus

2

secondary lymphoid organs

lymph nodes, spleen, MALT

3

MALT

mucosa associated lymphoid tissue
- Diffuse populations of lymphoid cells in the mucosa
- Lymphoid follicles of the GI, respiratory and genitourinary tracts
- Peyer’s patches of the ileum
- Tonsils

4

sources from lymphocytes

bone marrow (ULTIMATE)

5

bone marrow makes

1) T cell precursor that goes to thymus where they mature into helper and cytotoxic
2) Mature B cells
*both end up in secondary lymphoids

6

what do helper t cells do

activate cytotoxic t cells

7

what to cytotoxic t cells do

-Kill tumor cells, virus-infected cells, etc by contact
-Cell-mediated immunity

8

what do b cells transform into

plasma cells

9

what do plasma cells do

Kill by secretion of antibodies
Humoral immunity
(FROM B CELLS!!!!)

10

where is thymus found

superior mediastinum

11

how many lobes to thymus

2

12

what happens to thymus at puberty

undergoes involutions
(most active frombirth to puberty)

13

function of thymus (3)

1) Provides an environment where T cell precursors proliferate, mature and acquire their immunocompetence.

2) Supplies mature T cells to secondary lymphoid organs.

3) Secretes hormone-like substances which stimulate T cell proliferation and maturation.

14

major cell types in cortex of thymus

large lymphocytes (immature T)
small lymphocytes (maturing T)
epithelial reticular
macrophages

15

clonal selection is another term for

maturation

16

clonal selection

outer cortex large immature lymphocytes proliferate and divide, move through inner to corticomedullary junction. (React with body antigen as moving through or those that cant react die by apoptosis -- 95%!!)

17

positive selection

t cells that recognize non self antigens become mature (helper and cytotoxic) less than 5%

18

negative selection

React with body antigen as moving through or those that cant react die by apoptosis -- 95%!!

19

Apoptotic T cells are phagocytized by

macrophages - contribute to negative selection

20

what does negative selection do

prevents development of autoimmune disease

21

what are epithelial reticular cells linked by

desmosomes

22

epithelial reticular cells (what do they do)

present antigens to maturing T cells
instruct/educate maturing t cells to react or not react with antigens

23

thymulin, thymosin, thymopoietin

● Polypeptides secreted by epithelial reticular celThymic hormone-like substances

24

hassall's corpuscle

histo marker for thymus
first appear in fetal life and increase in number and size after
concentric layers of epithelial reticular cells

25

hassall's corpuscle histo description

Concentric layers of epithelial reticular cells that appear eosinophlic, keratinized and degenerative
* can secrete cytokines and phagocytose

26

thymic involution

thymus of elderly adult showing lymphoid tissue separated by adipose tissue
already have enough secondary t cells in organs to keep immunity