Lymphoid organs

Question 1

What are two antigen presenting cells

Answer 1

Macrophages and dendritic cells

Question 2

Central (primary) lymphoid organs

Answer 2

Bone marrow
thymus
production of lymphocytes

Question 3

Peripheral (secondary) lymphoid organs

Answer 3

Lymph nodes
Spleen
Tonsils
Peyer's patches
microenvironment for interaction of lymphocytes and antigens

Question 4

Aggregates of lymphoid tissue in non-lymphoid organs

Answer 4

Digestive system (GALT)
respiratory tract
urinary tract
reproductive tract
skin (SALT)

Question 5

Recirculation of lymphocytes

Answer 5

From blood to lymphoid organs and back to blood

• facilitates antigen recognition, lymphocyte proliferation and differentiation
• ensures rapid response to antigens
• connects three components of the immune system– Primary/secondary/extralymphoid

Question 6

B lymphocytes

Answer 6

Differentiate into plasma cells
humoral immunity
production of antibodies

Question 7

T lymphocytes

Answer 7

70-80% of circulating lymphocytes

cytotoxic lymphocytes

Question 8

Cell-mediated immunological responses

Answer 8

T-cell
against foreign cells
against bacterial or viral infected cells
against malignant cells

Question 9

T-cell mechanisms of killing

Answer 9

Production of perforin and granzymes

induction of apoptosis

Question 10

Reticular fibers

Answer 10

Cant be observed in H&E
reduce silver salts
composed of Type III collagen

Question 11

Reticular cells

Answer 11

originate from mesenchyme
functions
-synthesize and maintain reticular fibers and ground substance
-macrophage
-trophic role in blood cell maturation
-storage place of ferritin
-antigen presentation (dendritic cells)

Question 12

loose lymphoid tissue

Answer 12

Open meshwork of cells and fibers
fixed cells (reticular cells) most numerous

Question 13

dense lymphoid tissue

Answer 13

Denser meshwork of cells and fibers
free cells (lymphocytes) most numerous

Question 14

Nodular lymphoid tissue

Answer 14

Lymphocytes predominate
occurs in the form of spherical aggregates of cells
lack of connective tissue capsule
Primary and secondary nodules

Question 15

Primary nodules

Answer 15

Tightly packed small lymphocytes

not under antigenic challenge

Question 16

Secondary nodules

Answer 16

Have germinal centers

• subdivision- dark zone–dividing B lymphocytes
• light zone- non-dividing B lymphocytes and T helpers

Mantle zone- young plasma cells and memory B cells
-place of storage

Follicular dendritic cells and reticular fibers form framework

Question 17

Function of Secondary nodules

Answer 17

• Proliferation of activated B lymphocytes occurs in dark zone
• selection of B lymphocytes occurs in light zone
• apoptosis of B lymphocytes occurs in light zone
• surviving B lymphocytes begin differentiation into plasma cells and memory B cells in light zone
• temporary storage of young plasma cells and memory B cells takes place in mantle

These appear during primary antigenic response and involute after about 4 weeks

Question 18

General characteristic of lymph nodes

Answer 18

Blood vessels enter and leave at hilus

Efferent lymphatics leave at hilus

Question 19

Connective tissue trabeculae

Answer 19

Provide structural support

subdivide node into incomplete compartments

Question 20

Cortex

Answer 20

loose lymphoid tissue (sinuses)
Lymphatic nodules- may or may not have germinal centers
-contain mostly B lymphocytes

Question 21

Medulla

Answer 21

composed of dense lymphoid tissue (medullary cords)

-populated largely by B lymphocytes and plasma cells

Question 22

Medullary sinuses

Answer 22

Communicate with peritrabecular sinuses and efferent lymphatics
permeable walls- permit free passage of wandering cells

Question 23

Flow of lymph through node

Answer 23

Afferent lymphatics
-enter node @ multiple sites on convex surface
-valves open toward node
Subcapsular sinus
peritrabecular sinuses
medullary sinuses
efferent lymphatics
-leave node @ hilus
-valves point away from hilus

Question 24

filtration of lymph

Answer 24

occurs in sinuses

reticular cells are phagocytes- reticular cell failure facilitates spread of infection and/or metastases

Question 25

Lymphocyte circulation

Answer 25

produced in germinal centers
forced to periphery of nodules
enter sinuses
leave node by way of efferent lymphatics
enter blood circulatory system by way of thoracic duct

Question 26

High endothelial venules

Answer 26

have cell adhesion molecules

• selectins
• intergrins
• carbohydrates
• immunoglobulin superfamily members
• clever- 1

Play a role in lymphocyte recirculation
decrease in number with age
may be involved in metastasis of lymphoid malignancies

Question 27

recirculation is critical to efficient immune surveillance

Answer 27

Permits lymphocytes to encounter antigens
facilitates communication with other leukocyte types
allows targeting of lymphocytes

Question 28

paracortical zone

Answer 28

site of most HEVs
under thymic influence
-populated mostly by T lymphocytes

Question 29

function of lymph nodes

Answer 29

Filtration of lymph
production and selection of B lymphocytes
Play a role in the immune response to lymph-borne antigens

Question 30

Cortex of thymus

Answer 30

dense lymphoid tisse
lymphocytes predominate
site of thymocyte proliferation, apoptosis, and selection

Question 31

Medulla of thymus

Answer 31

Loose lymphoid tissue
rich in epithelial-reticular cells
site of thymocyte maturation

Question 32

Thymocytes

Answer 32

predominate in cortical regions
proliferate and undergo selection in cortex
populate T dependent regions of other lymphoid organs

Question 33

Epithelial reticular cells

Answer 33

Originate in endodermal lining of 3rd and 4th brachial pouches
not phagocytic
do not manufacture reticular fibers
Have a secretory function
-produce polypeptides promoting the differentiation of T lymphocytes
-thymopoietin
provide supporting framework
form hassall's corpuscles
contribute to blood-thymus barrier

Question 34

reticular cell of mesenchymal origin- dendritic cells

Answer 34

phagocytic

clean up debris resulting from T cell selection

Question 35

Functions of thymus

Answer 35

Development of T lymphocytes

• under influence of thymosin
• sensitive to radiation and chemotherapy

supports the development of the lymphoid system
-produces thymopoietin

Question 36

General characteristics of the Spleen

Answer 36

largest accumulation of lymphatic tissue in body

complex filter interposed in bloodstream

Question 37

Red pulp of spleen

Answer 37

large quantity of blood
two structures
-splenic sinuses- discontinuous BM with macrophages on outside- allow free exchange btwn cords and sinuses
-splenic cords- site of destruction of RBCs, site of storage of blood

Question 38

White pulp of spleen

Answer 38

composed of lymphoid tissue
periarterial lymphatic sheath (PALS)
-T dependent area
Lymphatic nodules
-located within the PALS
-contain mostly B lymphocytes
-May or May not have germinal centers

Question 39

Marginal zone of spleen

Answer 39

junction of red and white pulp
where most arterial blood runs through
contains- lymphocytes, dendritic cells and macrophages
site of initiation of immune responses to blood-borne antigens

Question 40

Pattern of blood flow through spleen

Answer 40

Splenic artery enters @ hilus
trabecular arteries
central arteries
penicilli
capillaries
splenic sinuses
red pulp veins
trabecular veins
splenic vein leaves the spleen @ hilus

Question 41

functions of spleen

Answer 41

production of lymphocytes
plays role in immune response to blood-borne pathogens
destruction of RBCs- in red pulp
storage of blood

Question 42

Palatine tonsils

Answer 42

Located in the lateral walls of the oropharynx
covered by stratified squamous epithelium
epithelium invaginated to form numerous deep crypts
surrounded by thick capsule of dense, irregular connective tissue

Question 43

Pharyngeal tonsil

Answer 43

Located in the roof of the nasopharynx
covered by pseudo stratified ciliated columnar epithelium
presence of numerous surface folds rather than deep crypts
surrounded by a thin capsule of dense, irregular CT

Question 44

Lingual tonsils

Answer 44

located @ base of the tongue
covered by stratified squamous epithelium
each lingual tonsil has a single large crypt

Question 45

function of tonsils

Answer 45

Detection and response to pathogens in the oral cavity

production of lymphocytes