lymphoid tissue

Question 1

lymphoid tissues

• contain
• provide
• structure

Answer 1

• masses of lymphoctyes and associated cells required to mount an immune response
• provides an environment that promotes immune cell-antigen interaction
• may exist as discrete lymphoid organs covered by epithelium or connective tissue capsule OR exist as isolated masses of cells within various organs that are in close proximity to the outside world

Question 2

4 lymphoid tissues

Answer 2

• spleen
• tonsil
• thymus
• lymph node

Question 3

primary lymphoid organs

Answer 3

• bone marrow and thymus
• BM = B cells
• thymus = T cells

Question 4

immunocompetency

Answer 4

-develooping B and T cells with antigen receptors which do not recgonize self

Question 5

thymus appearance

Answer 5

• starry sky

- continuous branched medulla

Question 6

cell migration in the thymus

Answer 6

-migrate to superior mediastinum and differentiate into epithelioreticular cells, and form a cytoreticulum

Question 7

thymic eptihelial cells

• what do they form
• what happens there
• what are these cells called

Answer 7

• form a cytoreticulum that becomes infiltrated by T-cell precursors (thymocytes)
• these epithelial cells are called epithelioreticular cells

Question 8

epithelioreticular cells

• what do they have
• what do they support
• what do they surround and why
• s subset of…
• how can they be visualized
• connected by what

Answer 8

• cytokeratin positive
• surround lymphocytes and macrophages
• support thymocytes (thymus has no supporting reticular fibers),
• surround caps and contribute to blood thymus barrier thus preventing foreing antigens from entering the thymus and being considered self
• a subset from Hassal’s corpuscle
• seen with keratin IHC
• connected by desmosomes

Question 9

Hassal’s corpuscles

• appearance
• where are they found
• function
• what do these diagnose

Answer 9

• whorls of epithelioreticular cells
• reside in thymic medulla
• poorly understood but appear to regulate T-cell (Tr) development
• these are diagnostic of the thymus

Question 10

germinal centers

-what do they contain

Answer 10

contain proliferating b cells

Question 11

diffuse area of lymphoid nodules

-what do these contain

Answer 11

-contain lymphocytes

Question 12

nodules

-what happens here

Answer 12

-B cells will enter Ct and differentiate into plasma cells

Question 13

mucosa associated lymphoid tissue (MALT)

-where

Answer 13

• lymphoid tissue found between the epithelial cells of the intestinal lumen and the muscularis mucosa
• within the lamina propria

Question 14

types of tonsils (3)

Answer 14

• pharyngeal
• palatine
• lingual

Question 15

palatine tonsils

• what do these contain
• epithelium

Answer 15

• germinal centers of lymphoid nodules
• glands
• lymph tissue
• striated muscle
• crypts for surface area
• stratified squamous NK epithelium

Question 16

pharyngeal tonsils

-epithelium…this is diagnostic

Answer 16

• respiratory epithelium

- many lymphocytes

Question 17

peyers patches

• where
• epithelium

Answer 17

• found in the lamina propria and extend to the submucosa of the ileum
• simple columnar

Question 18

M (microfold) cell

• function
• appearance

Answer 18

• allows lymphocytes to get very close to the apical surfecr by approaching the basal surface
• the basal surface has an invagination that comes up very close to the apical surface

Question 19

appendix functions

• 5
• cell type found here

Answer 19

• immune surveillance (abundant M cells)
• vestigal: former enlarged cecum
• endocrine organ: endocrine cells appear by 11th week in fetus
• reserve of gut microbiome : following loss due to diarrhea etc, the bacteria that live here will repopulate the gut
• surgical substitute for diseased ureters, sphincter in reconstructive bladder surgery

Question 20

lymph node

• size
• where
• function

Answer 20

• range from 1mm to several cm
• concentrated in neck, axilla, and groin
• filtered lymph and expose antigens to immune cells

Question 21

structural components of lymph nodes

Answer 21

• cortex
• paracortex
• medullary cords
• medullary sinuses

Question 22

medullary cord

-contains

Answer 22

• loose CT, highly cellular
• reticular fibers
• plasma cells
• lymphocytes
• fibroblasts
• neutrophils

Question 23

medullary sinus

• contains
• what type of endothelium

Answer 23

-venous channel running between cords, discontinuous endothelium, traversed by reticular fibers

Question 24

splenic cords and sinuses

-diferences between medullary cords/sinuses

Answer 24

• similar to lymph nodes but:
• have blood cells in both cords and sinuses
• sinuses are not traversed by reticular fibers
• sinuses have continuous endothelium

Question 25

three mechanisms assure interaction between lymphocytes and pathogens

Answer 25

1. sinuses are lined by a discontinuous endothelium so cells can slip out 2. reticular fibers traverse all sinuses 3. afferent lymphatics outnumber efferent; bottleneck results

Question 26

high endothelial venules | -what happens here

Answer 26

-this is where lymphocytes enter

Question 27

lymphodenopathy

Answer 27

-paracortical reaction following activation of HEV's

Question 28

spleen - function - during fetal development - stores what - recycles what

Answer 28

- immune response, B and T cells - destroys damaged senescent blood cells - sequesters monocytes - hematopoiesis (fetal development) - storage of blood/platelets - recylcing of iron

Question 29

red pulp cords - contains - cellular elements

Answer 29

- loose Ct/reticular fibers | - cellular elements: red blood cells, platelets, macrophages, plasma cells, and lymphocytes

Question 30

red pulp sinuses - type of endothelium - type of basal lamina

Answer 30

- venous channels lined by elongated, discontinuous endothelial cells - discontinuous basal lamina