2. Lymphoid I

Question 1

kinds of lymphocytes

Answer 1

B and T

T -> Killer, helper, suppressor

Question 2

Nodules

Answer 2

B-lymphocyte

have germinal centers (central light area) surrounded by Mantle (darker mature lymphocytes)

Question 3

Peyer’s patch

Answer 3

aggregated lymph nodules in intestine

Question 4

Lymphocyte activation

Answer 4

Helper T -> activate B-cell -> produce plasma cells/Ab -> They migrate to medullary cords of lymph nodes -> released into lymphatic vessels -> lymph node responds to antigen by producing more lymphocytes -> swollen glands

Question 5

Tcells

Answer 5

produce Helper/cytotoxic cells which act directly on virus or tumor

Question 6

B cells

Answer 6

produce plasma cells which produce Ab.

Question 7

lymphnode flow

Answer 7

Afferent lymph -> Subcapsular -> trabecular -> medllary sinus -> efferent

Question 8

capsule of lymph node

Answer 8

Dense connective tissue

continsues as trabeculae

Question 9

Stroma of lymph node

Answer 9

Reticular cells (fibroblast)
Reticular fibers (type III collagen)
fixed phagocytic cells

Question 10

Nodule of Lymphnode

Cortex of Lymphnode

Answer 10

Nodule B

Cortex T - non nodular lymphatic tissue

Question 11

Adult lymphocyte

Answer 11

Adult lymphocyte is smaller!

Question 12

cortex of lymph node

Answer 12

2 layers:
Outer - lymphoid nodules, primary nodules (circular solid mass of mature lymphocytes with some macrophages,dendritic cells), secondary nodules (germinal center)
Inner/Deep layer of Cortex - Dense collection of T

Question 13

Deep cortex = inner cortical layer = paracortical zone

Answer 13

a

Question 14

MEdullary sinus

Answer 14

Deep cortex extends into central medulla as narrow cords of lymphocytes -> separated by looser lymphatic tissue which form Medullary sinus

Question 15

Medulla

Answer 15

cords of B lymphocytes
Forms Efferent lymphatics
fixed phagocytic cells, macrophages, plasma cells

Question 16

Loose and Dense area of Medulla

Answer 16

Loose - medullary sinus

Dense - medullary cord

Question 17

Blood vessels of lymph node

Answer 17

found in dense lymphatic tissue of cortex and medulla

A. -> Cap. in cortex -> Post-cap. Venules in Deep cortex

Question 18

Where are the macrophages?

Answer 18

Macrophages are found in sinuses

Question 19

antigens in spleen

Answer 19

antigen is presented to Helper T or B -> generate plasma cells -> Ab released into system

Question 20

Capsule of Spleen

Answer 20

CT, it continues as trabeculae

Question 21

Stroma of Spleen

Answer 21

Reticular cells

Reticular fibers

Question 22

White pulp of spleen

Answer 22

B/T

20% of organ

Question 23

Red pulp of spleen

Answer 23

venous sinus/splenic cord (they are full of blood)

Question 24

There is no cortex in spleen

Answer 24

?

Question 25

Characteristics of white pulp

Answer 25

``` lymphocyte follicles (B) and non nodular aggregates (T) Irregular aggregation ```

Question 26

Whitepulp/redpulp

Answer 26

White pulp is bluish, rest is red pulp (red pulp - parenchyma, venous sinus) lymphocytes are concentrated in white pulp

Question 27

3 layers of nodule

Answer 27

Marginal layer - periphery (large cell) Mantle layer - in b/w marginal layer/germinal center (small) Germinal center - lymphoblasts

Question 28

Central artery of spleen

Answer 28

unique to spleen, usually in marginal layer

Question 29

sinuses of red pulp

Answer 29

thin capillary-like vessels lined by widely spaced endothelium. Minimal basal lamina and encircled by few reticular fibers.

Question 30

Marginal zone

Answer 30

narrow zone of modified red pulp adjacent to white pulp. receives blood from local small arterioles. small sinuses - site of lymphocytic emigration from blood and entry into white pulp. Antigen presenting cells in area.

Question 31

Characteristics of Spleen

Answer 31

large vessels supported by trabeculae Central artery Blood dumped into splenic cords is xposed to local macrophages Blood cells attain safety by passing into sinuses

Question 32

Blood Flow in spleen

Answer 32

Splenic a. -> trabecular a. -> central a. -> small arteriole in red pulp -> penicilli a. (discharge/dump blood into splenic cord to enter sinuses via their slits -> venule draining sinus -> larger venule -> trabecular vein -> splenic vein

Question 33

Function of spleen

Answer 33

Fetal - erythopoiesis, leukopoiesis Destruction of aged, abnormal red cells Sequesters monocytes to become macrophage platelet storage

Question 34

Thymus Embryology

Answer 34

derived from outpockets that pinch off from the pharynx stroma is epithelial descend to region of heart

Question 35

lymphocytes become T lymphocytes in thymus

Answer 35

a

Question 36

Thymus has 2 subdivisions

Answer 36

cortex of small lymphocytes lies beneath a thin capsule | medulla of fewer lymphocytes lies in the interior

Question 37

Thymus: Epithelial Reticular Cells

Answer 37

Form epithelial stroma of thymus Responsible for imparting immunocompetency upon developing T lymphocytes; via factors as thymosin, thymopoietin. Invest capillaries with additional external layer "Blood-Thymus" barrier in cortex Isolate developing lymphocyte into small groups

Question 38

Thymus: Cortex

Answer 38

Capsule - continue as trabeculae forming incomplete lobules Solid, dark-staining mass of lymphocytes Undifferentiated lymphocytes arrive from bone marrow, enter peripheral cortex, proliferate intensively, move towards medulla as they mature. 95% developing T cells are eliminated to prevent protential risk to self. Macrophages present

Question 39

Thymus: Medulla

Answer 39

Medulla of adjoining lobules observed to be continuous with one another. Stains pale: fewer lymphocytes Epithelial reticular cells apparent Thymic/Hassall's corpuscles - unique focal, concentric clumps of epithelial reticular cells, become cornified, gold standard for identification of thymus Mature immunocompetent lymphocytes arrive from coftex and exit thymus via venous outflow

Question 40

Thymus: Hassall's corpuscle

Answer 40

characteristic of Thymus Located in Medulla Formed as epithelial reticular cells that degenerate/undergo cornification increase as person ages

Question 41

Thymus: Involution

Answer 41

``` Hassall's corpuscles starts at puberty Concentration of lymphocytes diminish Fat cells appear Cortico-medullary distinction is lost ```