Lymphoid System Histology II

Question 1

The cortex of the thymus has more

Answer 1

Immature T-cells

Question 2

Enter near the thymic corticomedullary junction and migrate into the cortex where “education” into mature, immunocompetent T-lymphocytes begins

Answer 2

Immature T-lymphocytes

Question 3

In the outermost cortex, immature T-lymphocytes proliferate and undergo gene rearrangement to form pre-TCR with co-receptors

Answer 3

CD4 and CD8

Question 4

T-lymphocytes that recognize MHC but not selfantigen continue

Answer 4

Maturation

Question 5

ERCs that take up many developing T-cells into their cytoplasm and eliminate potentially harmful T-cells

Answer 5

Thymic Nurse cells

Question 6

Immunocompetent T-lymphocytes that survive the selection process reach the medulla for maturation completion and exit the thymus via postcapillary venules at the

Answer 6

Corticomedullary junction

Question 7

Developing thymocytes in the cortex require protection from exposure to

Answer 7

Antigens

Question 8

Consists of desmosome-linked ERCs plus basement membrane, perivascular CT, continuous capillary endothelium plus basement membrane

Answer 8

Blood/thymus barrier

Question 9

Additionally, nearby macrophages ensure escaping antigens from capillaries into thymus do not react with developing

Answer 9

T-cells

Question 10

Like the lymph node, the thymus has a cortex-medulla. Unlike the lymph node, the thymus does not have

Answer 10

Nodules

Question 11

Also, the thymus exhibits a key distinguishing feature within the medulla, the whorlshaped clusters of degenerating, eosinophilic, keratinized ERCs called

Answer 11

Hassall’s thymic corpuscles

Question 12

After puberty, the thymus slowly and progressively involutes, with loss of parenchymal T-cells and replacement by

Answer 12

Fatty connective tissue

Question 13

In elderly, the involuted thymus is mostly fat and has been linked to some loss of immune function with susceptibility to infection and

Answer 13

Cancer

Question 14

An inherited immunodeficiency in which thymus ERCs do not develop, which results in failed T-lymphocyte maturation

Answer 14

DiGeorge syndrome

Question 15

The equivalent of DiGeorge syndrome is the nude, athymic mouse strain that lacks transcription factor

Answer 15

Foxn1

Question 16

The stratified squamous epithelium at the surface and along deep crypts and absence of cortex-medulla helps distinguish tonsils from

Answer 16

Other lymphoid organs