chapter 3: thymus

Question 1

primary lymphoid organ that is two lobes extending over the great heart vessels

Answer 1

thymus

Question 2

involution of the thymus begins after puberty, first in the ___, second in the ____ and third in the ____

Answer 2

septa
cortex
medulla

Question 3

the function of the thymus is to _____ ______ ______

-this means they will distinguish self/nonself antigens and develop self tolerance

Answer 3

establish immunocompetent T lymphocytes

Question 4

t lymphoblast in the thymus

Answer 4

thymocyte

Question 5

4 types of thymic supportive tissue

Answer 5

capsule
septa
adipose
microstroma (TECs)

Question 6

thin delicate capsule of dense irregular CT with lobules w/ a periph cortex and central medulla

Answer 6

thymus structure

Question 7

thymic epithelial cell (TEC) AKA

-there are 6 types

Answer 7

epithelioreticular cells

Question 8

5 functions of thymic epithelial cells

Answer 8

1. support via cytoplasmic processes (no retic fibers)
2. secrete thymic hormones, cytokines
3. form thymic corpuscles
4. blood-thymic barrier
5. function as APC

Question 9

the secretion of thymic hormones and cytokines via the TECs do what two things

Answer 9

• influence T cell maturation, division, activities

- immunity elsewhere in body

Question 10

TEC type VI found only in medulla (never cortex) that varies in size and number and increases in both size and number with age

Answer 10

thymic corpuscles (hassall’s bodies)

Question 11

to secret cytokines to influence local dendritic cells and the development of some T cells is the function of what

Answer 11

thymic corpuscles (hassall’s bodies)

Question 12

-continuous capillaries w/ thick BL
-perivascular compartment (CT w/ macrophages)
-TEC type I w/ BL
all make up the:

Answer 12

blood thymic barrier

Question 13

-to prevent T cells from physically contacting foreign antigens in cortex is the function of the

Answer 13

blood thymic barrier

Question 14

the blood thymic barrier is only found around cortical capillaries and allows self molecules thru but will block

Answer 14

blood/lymph macromolecules

Question 15

the cortex of the thymus contains a high cell concentration, with large numbers of ____ and _____

Answer 15

t lymphocytes

macrophages

Question 16

the medulla of the thymus contains a lower cell density, with fewer but larger ___, ____, and the APC ____

Answer 16

t cells
macrophages
dendritic cells

Question 17

t lymphoblasts are prudced in the __ ___ and enter thymus as immunoincompetent T cells (thymocytes), then leave bloodstream at corticomedulllary line

Answer 17

bone marrow

Question 18

98% of t cells fail the positive selection process at the periph of cortex, which leads to

Answer 18

apoptosis

Question 19

if t cells survive, they can continue maturation thru the ___ __ ___ to become cytotoxic t & th cells

Answer 19

negative selection process

Question 20

these are lacking in the thymus

Answer 20

reticular fibers

reticular cells