Lymphoid System Histology II Flashcards

1
Q

The cortex of the thymus has more

A

Immature T-cells

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2
Q

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

A

Immature T-lymphocytes

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3
Q

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

A

CD4 and CD8

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4
Q

T-lymphocytes that recognize MHC but not selfantigen continue

A

Maturation

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5
Q

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

A

Thymic Nurse cells

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6
Q

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

A

Corticomedullary junction

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7
Q

Developing thymocytes in the cortex require protection from exposure to

A

Antigens

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8
Q

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

A

Blood/thymus barrier

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9
Q

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

A

T-cells

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10
Q

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

A

Nodules

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11
Q

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

A

Hassall’s thymic corpuscles

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12
Q

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

A

Fatty connective tissue

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13
Q

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

A

Cancer

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14
Q

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

A

DiGeorge syndrome

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15
Q

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

A

Foxn1

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16
Q

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

A

Other lymphoid organs