Lymphoid Organs

Lymphatc Sysem  Lymphatc vessels  1ºlymphoid organs  Thymus  Bone marrow  2ºlymphoid organs  Lymph nodes  Adenoids  Tonsils  Spleen  Appendix  SALT  ALT  BALT

A! "unctons 1! #emove excess inersttal $uid 2! Transpor o% dieary lipids &! Speci'c immuniy (as compared o non)speci'c immuniy*

Lymph organs and tssues +rimary (re,uired %or sem cell immunocompeance* i! red marrow produces all lymphoid precursor cells -u also .educaes. B)lymphocyes ii! hymus .educaes. pre)Tlymphocyes %rom -one marrow/ ma0ing maure T)lymphocyes! os actve untl pu-ery! •

PRIMARY LYMPHOID ORGANS +rimary lymphoid organs are where lymphocyes arise and maure in he a-sence o% antgenic stmuli! stmuli! They are he -one marrow marrow and hymus! hymus! Bone marrow: he so tssue in he hollow cener o% -ones Source o% all hemaopoietc progenior (sem* cells/ sie o% B cell mauraton pos)-irh in mammals! hemaopoietc sem cell sromal sem cell  secrees cyo0ines %or he stmulaton o% B) cell mauraton

Thymus Bilo-ed organ

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Locaed in he anerior mediastnum o% he horacic caviy anerior o he rachea and hear and grea vessels and poserior o sernum! •

Sie where lymphoid cells undergo mauraton and educaton ino T cells prior o release ino he circulaton! This process allows T cells o develop he imporan a3ri-ue 0nown as sel%)olerance! •

4specially imporan in new-orn -a-ies wihou a hymus a -a-y5s immune sysem collapses and he -a-y will die •

6radually 6radually enlarges during childhood

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Aer pu-ery i undergoes a process o% involuton resultng in a reducton in he %unctoning mass o% he gland! 7 contnues o %uncton hroughou li%e/ however! •

A! Sroma 1! capsule 2! ra-eculae ra-eculae (srands (srands o% connectve tssue ino ino parenchyma* parenchyma* a! lo-ules (ouer corex corex 8 inner medulla* &! 7nerdigiatng 7nerdigiatng dendritc cells  ma0e ma0e organ organ %rameowr0 %rameowr0 conri-ue o growh 8 mauraton o% hymocyes

B! +arenchyma 1! corex a! immaure T lymphocyes 7mmaure lymphoid cells ener he corex/ where hey proli%erae/ proli%erae/ maure/ and move o he medulla/ %rom where maure T lymphocyes ener he circulaton! 9urse cells  hymic epihelial cells wih long mem-rane exensions :ortcal epihelial cells  %orm newor0 -y long inerconnectng inerconnectng cyoplasmic exensions

2! medulla a! T lymphocyes ener venules -! ;assallrgans +eripheral lymphoid organs? lymph nodes/ spleen/ onsils/ adenoids/ and lymphoid tssue associaed wih oher organ sysems (gu/ s0in/ mucosa*! •

Along he vessels o% lymphatc sysem

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conrol he ,ualiy o% immune responses

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@ell organied 8 encapsulaed  Spleen 8 Lymph nodes •

=iused 8 unencapsulaed aggregaton o% lymphoid tssues  ALT ALT •

=ierences among he various lymphatc tssues signi'canly aec he %orm o% immuniy and relae o how antgens are ac,uired -y hese organs  •

lymph nodes are 'lers o% lymph/ spleen is a 'ler o% -lood/ and mucosal associaed lymphatc tssues ac,uire antgens -y ranscyosis o lymphoid tssue %rom he .exernal. environmen across specialied %ollicle)associaed epihelial cells

This drawing simpli'es srucures and connectons o% secondary lymphatc tssues where antgen may mos eCcienly direc immune responses! ultple 0nown and un0nown %acors inrinsic o he microenvironmens o% lymph node/ spleen and mucosa associaed lymphatc tssue (here ALT is represened -y +eyer5s paches* in$uence wheher a .peripheral. or .mucosal. ype o% response occurs! The drawing also indicaes ha hese tssues are inegraed wih each oher and he res o% he individual hrough vascular and lymphatc connectons and a sysem o% lymphocye recirculaton!

Lymph 9odes 4ncapsulaed 8 -ean shaped conaining lymphocyes/ macrophages 8 =: