LECTURE - The Lymphoid System Flashcards
functions of the lymphoid system
- adaptive immune system function
- removal of excess fluids from body tissues
- absorption of fatty acids
circulation of lymph
- lymph vessels begin as blind capillary-like vessels nearly everywhere
- collect excess fluid and transport it back to circulation
- on its way back, lymph passes through many lymph nodes
- lymph nodes smple lymph for presence of antigens
lymph nodes nearly everywhere but only some are superficial enough to be palpable or easily excised
- cervical
- supraclavicular (last check before bloodstream)
- axillary
- epitrochlear
- inguinal
- popliteal
primary lymphoid tissues
- lymphocyte production and maturation pre-antigen exposure
- bone marrow and thymus (anterior mediastinum)
secondary lymphoid tissues
- facilitate exposure and response to antigen
- BM (lacks lymphatic drainage), lymph nodes, spleen = lymphoid organs
- accessory lymphoid organs = appendix, tonsils and adenoids
- MALT = Peyer’s Patches in GI, BALT in airways, in urinary tract as well
The Lymphocytes
- B cells = CD20+; morphologically recognizable stages of maturation
- T cells = CD3+; mostly small lymphocytes
- NK-cells = CD16/56+; normally scant
non-lymphocytic cells in our immune system
functionally important but far less numerous
- APCs (dendritic cells)
- reticular cells (structural; e.g. fibroblasts)
- macrophages
- others
smallest nucleated cells in the body
small lymphocytes (mature)
B cells are mainly found in follicles
- mantle zone = antigen naive B cells
- germinal center = centroblasts and centrocytes
where are T cells mainly found?
interfollicular spaces
if lymph node is inflamed or affected in any way, this is a good screen
subcapsular sinus collapses
paracortical area
more T cells
spleen removal puts someone at risk for…
capsular bacterial infections
the thymus is most active..
before age of 5 years - then involutes
- trains T cells on how to distinguish self antigens from foreign
Hassall’s Corpuscle
- thymus
- composed of flattened reticular epithelial cells that have degenerated; arranged in concentric formation and may have some keratinization; function unknown
