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152 Cards in this Set

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What is lymph?

Excess tissue liquid

What is edema?

too much extracellular liquid in tissues

What does the lymphatic system do?

transports excess tissue liquid through lymphatic capillaries and vessels

What are the major functions of the lymphatic system?

transports, filters and returns lymph to venous circulation; provides defense (immunity) against "foreign" antigens.

What is innate immunity?

no requirement for previous exposure, non-specific action, immediate and rapid action

What is adaptive immunity?

requires previous exposure, recognition of diverse antigens, delayed action

What are examples of cells involved in innate immunity?

epithelial barriers, mast cells, granulocytes, macrophages, dendritic cells

What do antigen-presenting cells trigger?

adaptive immune response

what are examples of antigen-presenting cells?

macrophages, dendritic cells

What is lymphoid tissue?

specialized CT composed of parenchyma and stroma

Lymphocytes

What are the main cellular defenders?

lymphocytes

B lymphocytes

What type of response are B lymphocytes associated with?

Humoral (antibody) immune response

What are B lymphocytes activated by?

externalized antigens

What are examples of effector B lymphocytes?

plasma cells and B memory cells

What are T lymphocytes involved in?

cell-mediated immune response

What are T lymphocytes activated by?

internalized antigens. (APCs needed)

What are examples of effector T lymphocytes?

cytotoxic, helper, regulatory (supressor)

Parenchyma; packed lymphocytes are darkly staining

What is parenchyma?

the functional part

Stroma; reticular tissue except in thymus

What is the stroma?

the structural part

What do most lymphoid tissues have?

specialized form of post capillary venule

What is the specialized form of post capillary venue specifically called?

high endothelial venule (HEV)

What type of epithelium does the HEV have?

simple cuboidal epithelium

Where is the HEV found?

most lymphoid organs except spleen

simple cuboidal epithelium of the HEV

what does the HEV allow for?

lymphocyte movement back and forth between blood and local tissues

What is extravasation?

exiting blood vessel

what is recirculation?

return to blood vessel

What do primary lymphoid organs do?

produces and educates lymphocytes

where do immature lymphocytes form?

bone marrow

Where do immature lymphocytes become B cells?

bone marrow

where do immature lymphocytes become T cells?

in the thymus

What do secondary lymphoid organs contain?

both B and T lymphocytes

What are secondary lymphoid organs the site of?

B and T cell activation from nodules

What are examples of secondary lymphoid organs?

tonsils, lymph nodes, spleen

What type of lymphoid organ is bone marrow?

primary

What is the storm of bone marrow?

reticular tissue

what is parenchyma of bone marrow?

hemopoietic cells

what are the functions of bone marrow?

form generic lymphocytes; educate B lymphocytes

Bone marrow

What type of lymphoid organ is the thymus?

primary

What happens to T lymphocytes in the thymus?

they mature here

What is the site for T cell immunocompetence?

Thymus

What happens to the thymus with age?

it gets relatively smaller

When does thymus activity drop

after puberty

What is thymus tissue replaced by?

adipose CT

What is involution?

thymic tissue gradually replaced by adipose tissue

Does the stroma of the thymus contain reticular tissue?

no

Thymus epithelial cells

what functions as the stroma of the thymus?

thymus epithelial cells and their cytoplasmic processes

What do tight junctions between thymus epithelial cells create?

an isolated environment to direct immunocompetence

What is the thymus covered by?

CT capsule

What does the CT capsule do?

keeps maturing T cells in and antigens out

What divides thymus into incomplete lobules?

CT trabecula

Where are lobules connected?

at bases

Where do HEVs exist?

corticomedullary junction

What types of cells are found the thymic cortex?

lots of immature T lymphocytes; small nuclei

What are thymocytes?

immature T lymphocytes

What are characteristics of thymic epithelial cells?

large euchromatic nucleus with nucleoli

What are the characteristics and a function of macrophages?

poor-staining cytoplasm, phagocytose rejected thymocytes

What does the blood-thymus barrier in the thymus cortex do?

prevents unregulated exposure of immature thymocytes to antigens

What are immature thymocytes selected for?

immunocompetence in cortex

How many immature thymocytes pass selection to become helper or cytotoxic T cells?

only 2%

What are thymic (hassles) corpuscles?

old thymic epithelial cells with concentric layers

What can Thymic corpuscles be a visual cue to?

identify thymus

What does a thymic corpuscle look like?

cut onion

Thymic (Hassall's) corpuscles

What do lymphoid nodules reflect?

adaptive immune response to antigen

What lymphoid organs have nodules?

secondary; diffuse lympoid tissue and tonsils, lymph node, spleen

What are lymphoid nodules?

temporary reaction of T and B lymphocytes to specific antigen

What do unchallenged lympoid nodules look like?

diffuse arrangement

What do challenged lymphoid nodules look like?

nodular arrangement

Unchallenged

What does the secondary lymphoid nodule indicate?

B lymphocyte activation and proliferation

What are the components of secondary lymphoid nodules?

germinal center, mantle, surrounding helper T lymphocytes

What occurs in the Germinal Center?

generation area; plasma cells and B memory cells

What occurs in the mantle?

exiting effector/memory cells, nonproliferating B lymphocytes

What do helper T lymphocytes that surround nodules do?

help activate B lymphocytes

GC: germinal center


MZ: mantle


yellow arrows: helper T lymphocytes surrounding nodules

What do diffuse lymphoid tissue and tonsils do?

survey epithelial barriers

what do lymph nodes do?

filter (survey) lymph

what does the spleen do?

filter (survey) blood

What is another name for diffuse lymphoid tissue?

mucosa-associated lymphoid tissue (MALT)

Where is MALT found?

under epithelial barriers

Does MALT have a core or medulla?

no

Does MALT have a CT capsule?

no

What is MALT made up of?

randomly packed B and T lymphocytes

What percent of MALT are immune cells?

about 70%

What is a tonsil?

a large mass of MALT

What circles oral and nasal cavities?

tonsils; special collection of MALT

What are some characteristics of Tonsils?

no cortex or medulla, many lymphoid nodules, some tonsils have deep folds

what are the deep folds called in tonsils?

crypts

What is the only organ that surveys (filters) lymph?

lymph node

What is a lymph node surrounded by?

CT capsule

Where does dirty lymph enter?

through several afferent lymph vessels

Where does clean lymph exit?

through 1 -2 efferent lymph vessels

What is the stroma of lymph node?

reticular CT, forms skeleton

Reticular connective tissue stroma of lymph node

lymph node

Lymph flows through the node in sinuses

Subcapsular, trabecular, medullary sinuses

Subcapsular, trabecular, medullary sinuses

What are the sinuses lined with?

endothelium

what does the sinus do?

carry lymph

What do reticular fibers do?

span sinuses and slows down flow

What do APCs do?

filter antigens after reticular fibers slow down flow

reticular fibers that span sinuses

What is the hilum?

fissure where blood vessel enter and exits; efferent lymph vessels exit

What is the lymph node cortex divided into?

outer and deep

What does the outer cortex do?

houses nodules, site of B cell activation and proliferation

What occurs in the deep cortex?

no nodules, lots of HEVs -site for extravasation, a T-cell territory

What does the medulla of lymph node feature?

cords and sinuses

What forms medullary cords?

parenchyma

What is the medullary cord rich with?

T and B cells, macrophages, and many plasma cells

What are cords separated by?

medullary sinuses - dilated spaces

What can plasma cells do?

secrete antibodies into sinuses

medullary cords

What does the spleen survey (filter)?

blod antigens

What is the largest single lymphoid organ?

spleen

Where is the spleen located in the body?

in left upper quadrant of abdomen

What are the functions of spleen in a fetus?

hemopoiesis

What are the functions of spleen in an adult?

filter blood of antigens and remove aged RBCs

Spleen

Spleen

Is there a cortex or medulla of a spleen?

no, nodules are randomly scattered

can spleen filter lymph?

no, there is no afferent lymph vessels

What is the red pulp in the spleen?

blood-filled capillaries and splenic cords

what is the white pulp in the spleen?

lymphoid nodules

What pulp is acidophilic and what pulp is basophilic?

red pulp is acidophilic (RBC rich) and white pulp is strongly basophilic (lymphocyte rich)

What feeds blood to spleen?

splenic artery

what does the splenic artery do once inside the spleen?

branch into trabecular arteries

What do trabecular arteries branch into?

central arterioles

what do the central arterioles branch into?

penicillar arterioles

What do penicillar arterioles do?

dumb blood into splenic cords of red pulp - reticular tissue

what does open circulation allow for?

better antigen filtering of blood by APCs

How do RBCs in splenic cords (reticular CT) re enter venous circulation?

sinusoidal capillaries

What are some characteristics of sinusoidal capillaries?

large diameter, endothelial gaps, incomplete basal lamina

What activates white pulp?

APCs

What are around the central arteriole in white pulp?

T and B cells

T cells surround central arteriole

response of white pulp to antigen:


resting white pulp -->

apc in red pulp activates helper T cell in PALs -->

helper t cell activates B cells -->

Primary nodule expands and pushes PALs aside-->

B cells proliferate-secondary nodule -->

Plasma and memory B cells into sinusoid