Immune and lymphatic system II Flashcards Preview

Histology Exam III Material > Immune and lymphatic system II > Flashcards

Flashcards in Immune and lymphatic system II Deck (36):
1

Composition of Thymus

- Capsule
- Trabeculae
- Lobules

2

Composition of the Capsule of the Thymus

-Blood vessels
- Efferent lymphatics are present
----- NO AFFERENT LYMPHATICS PRESENT------
(therefore lymph does not circulate through the thymus)
- Extends Trabeculae (septa) into the parenchyma

3

Does the thymus contain afferent lymphatics

NO!!!!! (lymph does not circulate through the thymus)

4

The Trabeculae (Septa) of the thymus is composed of

delicate CT

5

What divides the thymus into incomplete lobules

Trabeculae (septa)

6

What is the function of the Trabeculae (septa) of the thymus

divides the thymus into incomplete lobules

7

Each lobule of the thymus is composed of

an outer, darker staining cortex and an inner, lighter staining medulla

8

The cortex of each lobule of the thymus is _____ staining

Dark

9

The cortex of thymus lobules stains densely with

basic dyes such as H and E

10

What is the cell population of the cortex of the thymus lobules

-Epithelial reticular cells, which secrete thymosin
- T cells in various stages of differentiation

11

Epithelial reticular cells in the cortex of thymus lobules secrete

Thymosin

12

Thymocytes (hematopoietic progenitor cells of the thymus) migrate from _____ to _____ areas

cortical areas to medullary areas

13

Blood vessels surrounded by continuous epithelial barrier in the thymus allows for

the thymus to maintain lymphopoiesis while segregated from antigens

14

The medulla of thymus lobules is ____ staining

light

15

The medulla of the thymus lobules is specialized to allow

entry channel into blood stream of mature lymphocytes

16

Capillary beds in the medulla of lobules in the thymus are

not sheathed by epithelial cells

17

Where are Hassall's corpuscles found

in the medulla of thymus lobules

18

Whorls of highly keratinized medullary epithelial cells

Hassall's corpuscles

19

Hassall's corpuscles produce

cytokine thymic stromal lymphopoietin

20

What is the function of cytokine thymus stream lymphopoietin

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

21

The thymus is most developed at

puberty

22

At birth the thymus weighs

10-15 grams

23

at puberty the thymus weighs

30-40 grams

24

The thymus involutes during

adolescence

25

The thymus has no

lymph follicles (nodules)
No afferent lymph vessels
no lymph sinuses

26

Double negative T cells

- Lack cell surface molecules typical of mature T cells
- enter cortex from blood vessels
- proliferate in subcapsular area

27

Double negative T cells proliferate in

subcapsular area of the thymus

28

Double negative T cells enter the cortex of the thymus

from blood vessels

29

Double negative T Cells lack

cell surface molecules typical of mature T cells

30

Double positive T cells move to

outer cortex of thymus

31

Double positive T cells are confronted with _________ for ____ selection

epithelial cells with cell surface MHC classes I and II for clonal selection

32

Double positive T cells express

CD4 and CD8 coreceptors and TCR receptors

33

Single positive T cells move to the

inner cortex of the thymus

34

Single positive T cells express

TCR receptors and either CD4 or CD8 coreceptors

35

Clonal deletion is completed in the

medulla of the thymus lobules

36

What is the purpose of clonal deletion

to protect from autoimmune disease