The Lymphoid System Flashcards
where are haematopoietic stem cells made
foetal liver
postnatal bone marrow
where are B cells matured
bone marrow
where are T cells matured
thymus
what are the central/ primary lymphoid tissues
bone marrow
thymus
what are the peripheral/ secondary lymphoid tissues
lymph nodes spleen tonsils waldeyers ring) epithelio-lymphoid tissues bone marrow
what are the main roles of the lymphoid system
filtration of circulatory fluids
location for cells of the immune system (lymphoid and accessory)
what are the functions of the lymphatic system (nodes and lymphatics)
return lymph to the circulation
- maintains fluid homeostasis
- prevents tissue oedema
permits:
- cell traffic
- cell trapping
- mixing of cells and molecules with cells of the immune system
what can happen to arm after breast cancer surgery
lymphoedema
what is chylous ascites
leakage of lipid rich lymph into peritoneal cavity due to disruption of lymphatic system (usually mass or trauma e.g. iatrogenic)
can lymph nodes be imaged radiologically
yes major groups can e.g. mediastinal, para aortic
where do lymphatic vessels end
are blind ending- collect fluid from tissues and return it to blood stream
what created flow in lympathics
passive movement, valves ensure direction of flow
what is the structure of a lymph node
afferent channels drain through the capsule of the node into the peripheral sinus
lymph filters through the node parenchyma
efferent vessel leaves through the hilum
arterial and venous vessels serving the node also enter and exit at hilum
where does lymph re enter the venous system
at the junction of L or R subclavian and jugular veins
where does lymph go after leaving the node
- cisterna chyli/ thoracic duct
- L jugular, subclavian or bronchomediastinal trunks
- R jugular, sublacavian or bronchomediastonal trunks
then into venous system
how is lymph filtered in the node
via interactions between cells in the node and cells/ substances in the lymph fluid
what is lymphs role in the immune system
nodes house cells of the innate and immune system
traffic of immune presenting cells links innate and adaptive immune responses
what cells are housed within lymph nodes
lymphocytes: B cells (plasma cells, mainly in medulla), T cells, NK cells
non nuclear phagocytes (macrophages), antigen presenting cells and dendritic cells
endothelial cells
what is lymphadenopathy
lymph node enlargement (can be localised/ wide spread/ generalised and peripheral/ central (internal))
what can cause lymphadenopathy
local inflammation: infection, vaccination, dermatopathic
systemic inflammation: infection e.g. viral infections, autoimmune/ CTD
malignancy: haematological (lymmphoma/ leukaemia), mets
sarcoidosis
castlemans disease (IgG4)
what is sarcoidosis
multisystem granulomatous disorder of unknown cause
what should you examine in a patient with regional lymphadenopathy
the territory that drains to that group of nodes
what might you see in lymphangitis
red line extending from an inflamed lesion along path of lymph drainage
what can superficial lymphadenopathy be a sign of
underlying malignancy
what does generalised lymphadenopathy suggest
systemic inflammation/ widespread malignancy (lymphoma/ leukaemia)
what test should you always do in generalise lymphadenopathy
FBC
what causes predominantly B cell response in lymph node
autoimmune conditions and infections
what causes a predominantly phagocytic response in lymph nodes
if they are draining a tumour site
what causes a predominantly t cell response in lymph nodes
viral infections and drugs (e.g. phenytoin)
what is lymphoma
types of cancer developed from lymphocytes
where is the spleen
upper left quadrant
what is the anatomy of a healthy spleen like
150-200 g
has diaphragmatic surface and a visceral surface (left kidney, gastric fundus, tail of pancreas, splenic flexure of colon)
what is the vasculature supply to the spleen
splenic artery (branch of coeliac axis) drain by splenic vein (forms portal vein with SMV)
what can rupture the spleen
trauma (diseased spleen more likely to rupture)
describe the structure of the spleen
encapsulated
parenchyma made of red and white pulp
red pulp contains:
-sinusoids (fenestrated, lined by endothelial cells, supported by reticulin loops)
-cords (contain macrophages, fibroblasts, cells in transmit (RBCs, WBCs, plasma cells and CD8+ T cells)
white pulp= the peri-arteriolar lymphoid sheath
-CD4+ T cells
what is the role of the spleen
filters the blood:
- detects, retains and eliminates unwanted foreign or damaged material
- facilitates immune responses to blood borne antigens
what is the role of the white pulp in the spleen
is expanded by lymphoid follicles - shows reactive changes
antigens reaches white pulp by blood
APCs in the white pulp present antigen to immune reactive cells
what are the features of splenic enlargement
draggin sensation in LUQ
discomfort when eating
pain if infarction
what is the triad of hypersplenism
splenomegaly
fall in one/ more cellular components of blood
correction of cytopenias by splenectomy
what can cause splenomegaly
infection (EBC, malaria, TB, typhoid, brucellosis, leishmaniasis, trypanosomiasis)
congestion (portal: hepatic cirrhosis , portal/splenic vein thrombosis, cardiac failure)
haem diseases (lymphoma, leukaemia. haemolytic anaemia, ITP, myeloproliferative disorders)
inflammatory conditions (RA, SLE)
storage diseases (gauchers, niemann pick disease)
miscellaneous (amyloid, tumours, cysts)
what types of conditions are associated with hypersplenism
those that cause splenomegaly
what causes hyposplenism
most commonly- splenectomy coeliac disease sickle cell sarcoidosis iatrogenic
what are the features of hyposplenism
(result from reduced red pulp function)
howell jolly bodies
red cell abnormalities
