Chpt 3 (Thymus)

Question 1

Stages of involution following puberty

Answer 1

1. Septa
2. Cortex
3. Medulla

Little function by age 25

Question 2

Thymocyte is a

Answer 2

T lymphoblast in the thymus

Question 3

Thin delicate capsule of

Answer 3

Dense irregular CT

Question 4

4 types of thymic supportive tissue

Answer 4

1. Capsule
2. Septa
3. Adipose
4. Microstroma (TECs = thymic epithelial cells)

Question 5

2 names for TECs

Answer 5

Epithelioreticular cells

Thymic epithelial cells

Question 6

How many types of TECs are there

Answer 6

6

Question 7

5 functions of TECs

Answer 7

1. Support using cytoplasmic processes
2. Secrete thymic hormones and cytokines
3. Form thymic corpuscles (Hassall’s bodies)
4. Important component of the blood-thymic barrier
5. Function as APCs

Question 8

What do TECs NOT produce

Answer 8

Reticular fibers

Question 9

What type of TEC produces thymic corpuscles and where

Answer 9

Hassall’s bodies formed by TEC type VI in medulla

Question 10

What happens to Hassall’s bodies as we age?

Answer 10

They increase in size and number

Question 11

Hassal’s bodies secrete cytokines to influence _______________ and the development of _________________

Answer 11

Local dendritic cells

Some T cells

Question 12

TECs only influence the thymus

Answer 12

No, they affect immunity elsewhere in the body as well

Question 13

Blood thymic barrier found only in

Answer 13

Cortex

Question 14

The blood-thymic barrier consists of: (3 things)

Answer 14

1. Continuous capillaries with a thick basal lamina
   (also note paricytes outside of the basal lamina)
2. Perivascular compartment: CT with many macrophages to destroy foreign molecules
3. TEC type I with a basal lamina

Question 15

Perivascular compartment: CT with many

Answer 15

Macrophages to destroy foreign molecules

Question 16

Function of blood-thymic barrier

Answer 16

To prevent T cells from physically contacting foreign antigens

Question 17

Why is the blood-thymic barrier only around cortical capillaries?

Answer 17

Allows self- molecules through but will block blood/lymph macromolecules

Question 18

Cortex contains high cell concentration.

3 cell types are

Answer 18

1. T lymphocytes (large numbers)
2. Macrophages (large numbers)
3. TEC types I, II, III

Question 19

Medulla contains a lower cell density

4 cell types

Answer 19

1. Fewer but larger T cells (than cortex)
2. Macrophages
3. Dendritic cells: an APC
4. TEC type IV, V, VI

Question 20

3 things lacking in the thymus

Answer 20

1. Afferent lymph vessels
2. Reticular fibers
3. Reticular cells