Md1 Histology Block 3 Lymph 2 Part 1

Front 1

lymphoid tissues have two principal components:

Back 1

framework of reticular fibers
(type III collagen)


Free cells- Lymphocytes
(chiefly), macrophages,
plasma cells

Hint 1

A framework of reticular fibers (type III collagen) secreted by reticular cells which are indistinguishable from fibroblasts. The epithelial reticular cells of the thymus are an exception to this generalization.


Free cells- Lymphocytes (chiefly), macrophages, and plasma cells occupy spaces between the reticular cells and fibers. Each lymphoid organ or tissue has its own special organizational features.

Front 2

Lymphatic Tissue

three categories depending upon the connective tissue covering

-Unencapsulated 1
*Diffused lymphatic tissue 1
>Partially encapsulated 1
~Encapsulated 3

Back 2

Unencapsulated
-Free cells

Diffused lymphatic tissue
>Lymph nodule

Partially encapsulated
*Tonsils

Encapsulated
~Thymus
~Lymph nodes
~Spleen

Front 3

Unencapsulated lymphoid tissue

Back 3

-Free cells-
-Diffused lymphatic tissues
-(MALT)
mucosa assoc lymphatic tissue
-Lymphocytes,
-IgA = secreting plasma cells,
APCs,
T cells,
CD4+ helper cells predominate.
These cells are strategically located to intercept antigens and initiate an immune response


-Lymph nodules
Primary Nodule
Secondary Nodule
rapid proliferation
contains
lymphoblasts and plasmablasts)

Peyer’s patches in the small
intestine, or as large
aggregations in lymphatic organs.

Front 4

Luminal antigens are captured by dome-shaped cells called =

Back 4

M cells

present in the covering of

Peyer's patches
and transported to the subjacent region.

Front 5

M cells =

Back 5

mucosal immunity in the intestine.
Luminal antigens are captured by dome-shaped M cells present in the covering of Peyer's patches and
transported to the subjacent region.

Front 6

Partially encapsulated lymphoid tissue
= 4ct

Back 6

Tonsils
1-Palatine tonsils:
2. Lingual tonsils
3. Pharyngeal tonsils
4. Tubal tonsils

Front 7

Encapsulated lymphoid organs

Back 7

Thymus

Front 8

decribe the Thymus =

Back 8

-bilobed
-lymphoepithelial
-superior mediastinum
-The thymus develops early
-well developed before birth
-involute
-atrophy
-After puberty
replaced by
fatty and fibrous tissues

Front 9

Thymus
Produces the =

Back 9

T-lymphocytes

THymus Monitors T-cell production

Hint 9

It destroys the T-cells capable of attacking self

Front 10

T/F
THymus has no Afferent lymph vessels only
Efferent

Back 10

T

Front 11

T-cells are released by the thymus to complete their maturation in the =
2ct

Back 11

spleen
or
lymph nodes.

Front 12

Thymus
Each lobule is divided into two zones:

Back 12

-peripheral zone rich in lymphocytes called cortex


-central zone relatively rich in epithelial cells called the medulla.

Info

Hint 12

Structure

Capsule - The thymus is surrounded by a connective tissue capsule.
Trabecular septa extend from the capsule to divide the gland into lobules
The capsule and trabeculae contain blood vessels, efferent (but not afferent) lymphatic vessels and nerves.
Each lobule is divided into two zones:

Front 13

Hormones acting on the thymus
promote the formation of T cells =
5ct

Back 13

Thymosin
thymopoietin
thymulin
thymic humoral factor
Thyroxin

Thyroxin encourages _________
causes production of ______________
_____

Hint 13

Thyroxin encourages thymulin production by epithelialreticular cells.

Front 14

depress T cell formation in the thymus.

Back 14

Adrenocorticosteroids

Front 15

Epithelioreticular cells
do what

Back 15

provide a framework for the developing T cells.

Front 16

Thymic cortical cells (besides lymphocytes):

Epithelioreticular cells of six type

Back 16

Type I
separate the thymus parenchyma from connective tissue

Type II:
(thymic nurse cells)
Type III:
form functional barrier between cortex and medulla.
Like type II cells, type III cells express MHC I and MHC II molecules.

Front 17

Medulla stains less intensely than the cortex.

Three types of epithelioreticular cells are present in medulla:

Type IV: are located between cortex and medulla close to type
Thymic medulla

Back 17

Type IV:
between cortex and medulla close to type III cells.
located throughout the medulla.

Type VI:
thymic or Hassall’s corpuscle.
have flattened nuclei.
They produce thymic hormones (e.g. thymosin, thymopoietin).

Hint 17

Front 18

blood – thymic barrier.

Back 18

present in cortex only

Front 19

present in cortex only

Back 19

blood – thymic barrier.

Front 20

Lymphocytes reaching the thymic cortex are prevented from contact with antigens by a physical barrier called

Back 20

blood – thymic barrier.
It is present in cortex only

Front 21

During the process of differentiation T-cells will develop subsets markers that distinguish various types of
T- cells
such as =
6ct

Back 21

helper T-cells
cytotoxic T-cells
gamma-delta
T cells and regulatory
suppresser T­ cells
Thy-1,

Front 22

Thy-1, identify =

Back 22

all subtypes of T-cells in the
thymus
and
in the recirculating lymphocyte pool.

Front 23

Most T cell development takes place in the Medulla or cortex =

Back 23

cortex

Front 24

Deep in the cortex, maturing T cells are double-positive

Back 24

CD4+ and CD8+
and become receptive to
peptide-MHC complexes.

Front 25

Degeorge Syndrome =

Back 25

affects the production of functional T cells. The development of_________ is not affected in DiGeorge syndrome.

Hint 25

B cells

Front 26

MHC class II molecules are required for the development of =

Back 26

CD4+ T cells

Front 27

MHC class I molecules are necessary for the development of

Back 27

CD8+ T cells

Front 28

T cells that recognize both
self-MHC
and
self-antigens
-produced by thymic medullary epithelial cells under the regulation of the
AIRE gene.

What happens to them =

Back 28

eliminated by negative selection

Front 29

T/F

Those lymphocytes that fail to meet appropriate antigens do not survive in the spleen.

Back 29

T

Front 30

If the thymus of a newborn is removed, the following effects occur:

Back 30

no formation of T-lymphocytes
decrease
of lymphocytes in blood and lymph
depletion
thymus dependent areas of lymphoid tissues and organs.
no delayed hypersensitivity reaction
no graft rejection.

Front 31

the transcription factor Foxn1 necessary for the differentiation of thymic epithelial cells and epidermal cells

info

Back 31

.

Front 32

The human autosomal disorder called autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy
(APECED)
Does what =

Back 32

-autoimmune destruction of endocrine organs
-the inability to eliminate Candida yeast infection,
-development of ectodermal dystrophic tissue.