Lymphoid lab Flashcards
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
