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Flashcards in Lymphoid lab Deck (31):

Name the lymphoid organs

- thymus
- lymph nodes
- spleen
- tonsils
- peyer's patches & mucosa-associated lymphoid tissue`


What is a primary lymphoid organ and give an example?

Organs where lymphocytes are formed and mature by providing an environment for stem cells to divide and mature into B and T cells

- The thymus is a primary lymphoid organ


What are secondary lymphoid organs and list them

Are a series of filters that monitor the contents of extracellular fluid

Where lymphocytes are activated

- lymph nodes
- spleen
- tonsils
- peyer's patches & mucosa associated lymphoid tissue


Describe the general features of the thymus

- located in the anterior superior mediastinum

- consists of two lobes both of which have a central medulla and a peripheral cortex surrounded by an outer capsule

- thymus provides inductive environment for the development of T cells and selection of self-tolerant T cells


Describe the general features of the spleen

- produces immune cells to fight antigens
- remove particulate matter and aged blood cells
- produce blood cells during fetal life

synthesises abs in white pulp


What is white pulp?

Histological designation for regions of the spleen

consists entirely of lymphoid tissue


Describe the general features of the lymph nodes

consists of lymphoid follicles in outer cortex, which surrounds the inner medulla on all sides except at the hilum, which makes the nodes bean shaped.


What is the paracortex

immediately surrounds the medulla.

Unlike the cortex, contains an mixture of mature and immature T cells


What is a sentinel lymph node?

The hypothetical first lymph node or group of nodes draining a cancer


What is a lymph follicle?

dense collection of lymphocytes


Describe the capsule of a lymph node

composed of dense irregular connective tissue with some plain collagenous fibers

capsule contains a rich blood supply

is thicker in some areas than others in an irregular pattern


What is he subcapsular sinus?

The space between the capsule and the cortex, where lymph flows through


Where are the T cells found in a lymph node?

deep cortex


Where are B cells found in a lymph node?

outer cortex and medullary cords


Describe the blood supply and drainage of the lymph nodes

- nodal vein
- nodal artery

= nodal vessels

enter/exit the hilum of the node


What is Di George syndrome?

child born without a thymus

therefore no T cells and no cell mediated immunity


Describe the flow of lymph through vessels

vessels have no valves

lymph flow aided by muscular movement that 'milks' lymph


Describe mechanical filtration of lymph

settling tank of lymph node

rate of flow slows down in the subscapular sinus allowing filtrate to be removed from the lymph


Describe biological filtration of lymph

phagocytosis by macrophages


What histological sign is present in during an active lymphoid response?

presence of oval lymphoid nodules in the outer cortex


What is a lymphoid nodule and why do they form?

B cell feature

- Ag enters node
- B cell with affinity will bind
- proliferation of B cells
- small > medium > large cells as they divide and get more cytoplasm


Describe the histological features of a lymphoid nodule

- oval body
- light pole and dark pole
- germinal centre
- cap/carona of small lymphocytes

cap faces the source of foreign material


Which layer of the appendix is lymphoid tissue found?

- bulk in submucosa
- some found in lamina propria


Describe the histology of white pulp

- central arteriole adjacent to white pulp
- white when fresh, purple when stained
- T cells immediately around the arteriole
- B cell further out


What is the time span for lymphoid nodules?

- appear for a few days during infection then begin to dissappear

- macrophages slower to leave, leaving a 'reaction centre'


Describe the epithelium of the tonsils

stratified squamous non-keratinised epithelium, typical of the mouth


Describe the histology of tonsils

also contains skeletal muscle cells


Which of the tonsils has distinct features?

Palatine tonsil contains tonsilar crypt

The crypt epithelium hugely infiltrated by lymphocytes = very difficult to see

crypt contains micro-organisms and sloughed off cells = allows lymphocytes to get good exposure to microorganism to amount a response


Describe the histology of the thymus

contains partitions that breaks it into lobules

paler part = medulla
darker parts = cortex where lymphocytes are programmed


How can you differentiate between a childs thymus and an adults?

- T cells activate in childhood

- thymus involutes and replaced by fatty tissue in adults


Does the thymus engage in an immune response?

no - primary lymphoid organ