Thymus

Question 1

Production of B lymphocytes occurs primarily in the ____. Production of T lymphocytes occurs primarily in the ____.

Answer 1

Bone Marrow

Thymus

Question 2

Carrying out immune responses generally occurs in ____.

Answer 2

Secondary lymphoid organs and lymphoid tissue

Question 3

Examples of secondary lymphoid organs

Answer 3

lymph nodes
spleen
tonsils

Question 4

MALT

Answer 4

mucosa-associated lymphoid tissue

Question 5

In hollow organs lymphoid tissue is most often found in the layer called the _____.

Answer 5

Lamina propria

Question 6

GALT

Answer 6

gut associated lymphoid tissue

Question 7

Daughter cells differentiate into ____ and _____ .

Answer 7

Effector cells

Memory cells

Question 8

Thymus begins to develop at about the ___ week of gestation.

Answer 8

5th

Question 9

Thymus develops from the endodermal epithelium of the ___________.

Answer 9

3rd pharyngeal pouch

Question 10

Where does the thymus fuse across?

Answer 10

The midline in the thorax

Question 11

Thymus is initially composed of only _______ called _______.

Answer 11

Epithelial cells

Thymic Epithelial Cells (TECs)

Question 12

TECs are connected by ______.

Answer 12

desmosomes

Question 13

Capusle of Thymus is made up of ______.

Answer 13

Denser irregular CT with collagen 1 and reticular fibers

Question 14

Where thymocyte precursors enter the thymus.

Answer 14

Corticomedullary boundary

Question 15

Where thymocytes leave the thymus

Answer 15

via postcapillary venules at the corticomedullary junction OR via lymphatics

Question 16

the blood-thymus barrier in the cortex consists of:

Answer 16

1. capillary endothelial cells
2. basal lamina of endothelial cells
3. A perivascular space containing CT cells and fibers
4. basal lamina of the TECs
5. A continuous layer of Type 1 TECs joined by tight junctions

Question 17

blood-thymus barrier is _______ in the medulla

Answer 17

leakier

Question 18

Positive selection occurs in the _____

Answer 18

cortex

Question 19

Negative selection occurs mainly in the _____

Answer 19

medulla

Question 20

What identifies TECs as epithelial cells rather than connective tissue cells?

Answer 20

tonofibrils composed of cytokeratin

Question 21

TEC secreted cytokine that induces thymocyte division

Answer 21

TECK and SDF-1

Question 22

Type 5 TECs form ____ corpuscles in the medulla

Answer 22

Hassall’s

Question 23

Cortical TECs

Answer 23

Type 1
Type 2 (nurse cells)
Type 3

Question 24

Medullary TECs

Answer 24

Type 4
Type 5
Type 6

Question 25

Medullary TEC involved in negative selection

Answer 25

Type 5

Question 26

Type 5 TECs are connected by _____

Answer 26

desmosomes