Immune and lymphatic system II

Question 1

Composition of Thymus

Answer 1

• Capsule
• Trabeculae
• Lobules

Question 2

Composition of the Capsule of the Thymus

Answer 2

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

Question 3

Does the thymus contain afferent lymphatics

Answer 3

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

Question 4

The Trabeculae (Septa) of the thymus is composed of

Answer 4

delicate CT

Question 5

What divides the thymus into incomplete lobules

Answer 5

Trabeculae (septa)

Question 6

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

Answer 6

divides the thymus into incomplete lobules

Question 7

Each lobule of the thymus is composed of

Answer 7

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

Question 8

The cortex of each lobule of the thymus is _____ staining

Answer 8

Dark

Question 9

The cortex of thymus lobules stains densely with

Answer 9

basic dyes such as H and E

Question 10

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

Answer 10

• Epithelial reticular cells, which secrete thymosin

- T cells in various stages of differentiation

Question 11

Epithelial reticular cells in the cortex of thymus lobules secrete

Answer 11

Thymosin

Question 12

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

Answer 12

cortical areas to medullary areas

Question 13

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

Answer 13

the thymus to maintain lymphopoiesis while segregated from antigens

Question 14

The medulla of thymus lobules is ____ staining

Answer 14

light

Question 15

The medulla of the thymus lobules is specialized to allow

Answer 15

entry channel into blood stream of mature lymphocytes

Question 16

Capillary beds in the medulla of lobules in the thymus are

Answer 16

not sheathed by epithelial cells

Question 17

Where are Hassall’s corpuscles found

Answer 17

in the medulla of thymus lobules

Question 18

Whorls of highly keratinized medullary epithelial cells

Answer 18

Hassall’s corpuscles

Question 19

Hassall’s corpuscles produce

Answer 19

cytokine thymic stromal lymphopoietin

Question 20

What is the function of cytokine thymus stream lymphopoietin

Answer 20

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

Question 21

The thymus is most developed at

Answer 21

puberty

Question 22

At birth the thymus weighs

Answer 22

10-15 grams

Question 23

at puberty the thymus weighs

Answer 23

30-40 grams

Question 24

The thymus involutes during

Answer 24

adolescence

Question 25

The thymus has no

Answer 25

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

Question 26

Double negative T cells

Answer 26

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

Question 27

Double negative T cells proliferate in

Answer 27

subcapsular area of the thymus

Question 28

Double negative T cells enter the cortex of the thymus

Answer 28

from blood vessels

Question 29

Double negative T Cells lack

Answer 29

cell surface molecules typical of mature T cells

Question 30

Double positive T cells move to

Answer 30

outer cortex of thymus

Question 31

Double positive T cells are confronted with _________ for ____ selection

Answer 31

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

Question 32

Double positive T cells express

Answer 32

CD4 and CD8 coreceptors and TCR receptors

Question 33

Single positive T cells move to the

Answer 33

inner cortex of the thymus

Question 34

Single positive T cells express

Answer 34

TCR receptors and either CD4 or CD8 coreceptors

Question 35

Clonal deletion is completed in the

Answer 35

medulla of the thymus lobules

Question 36

What is the purpose of clonal deletion

Answer 36

to protect from autoimmune disease