histology of lymphatic system

histology of lymphatic system

1. Histology of Lymphatic system
Faseeh

2. Lymphoid system
•Themainfunctionofthelymphoidorgansisto
protecttheorganismagainstinvadingpathogens
orantigens.
•Lymphocytes,widelydistributedinbodyeitheras
singlecells,asisolatedaccumulationsofcells,as
distinctnon-encapsulatedlymphaticnodulesin
thelooseconnectivetissue,orasencapsulated
individuallymphoidorgans.
•Mainfocusinthislab:
–Lymphnodes,Spleen,Thymus(encapsulated)
–Tonsils(Non-encapsulated)

3. Lymph nodes
•Connectivetissuecapsulesurroundsthelymph
nodeandsendsitstrabeculaeintoitsinterior.
•Eachlymphnodecontainsanoutercortexandan
innermedulla.
•Cortex
–Anetworkofreticularfibersandspherical,non-
encapsulatedaggregationsoflymphocytescalled
lymphoidnodulescharacterizethecortex.
•lymphoidnodulesexhibitlighter-stainingcentralareascalled
germinalcenters.

4. Lymph nodes
•Medulla:
–consists of medullary cords and medullary
sinuses.
•Medullary cords are networks of reticular fibers filled
with plasma cells, macrophages, and lymphocytes.
•M. cords are separated by capillary-like channels called
medullary sinuses.

8. Spleen
•largelymphoidorganwitharichbloodsupply.
•Aconnectivetissuecapsulesurroundsthespleen
anddividesitsinteriorintoincomplete
compartmentscalledthesplenicpulp.
–Whitepulpconsistsofdark-staininglymphoid
aggregationsorlymphaticnodulesthatsurrounda
bloodvesselcalledthecentralartery.
–Redpulpconsistsofspleniccordsandsplenic
(blood)sinusoids.

11. Thymus gland
•Soft,lobulatedlympho-epithelialorgan.
•Thethymusglandissurroundedbyaconnective
tissuecapsule.
–adark-stainingcortex
•immaturelymphocytesthatmigrateherefromhemopoietic
tissuesinthedevelopingindividualtoundergomaturationand
differentiation.
–AlightstainingMedulla
•epithelialcellsformacoarserframeworkthatcontainsfewer
lymphocytesandwhorlsofepithelialcellsthatcombinetoform
thymic(Hassall’s)corpuscles.

14. Palatine Tonsil
•consist of aggregates of lymphatic nodules located in the oral
cavity.
•palatine tonsils are not surrounded by a connective tissue
capsule.
•surface of the palatine tonsil is covered by a protective stratified
squamous nonkeratinizedepithelium.
•Each tonsil is invaginatedby deep grooves called tonsillar
crypts.
•the underlying connective tissue have numerous lymphatic
nodules, distributed along the lengths of the tonsillarcrypts.
•dense connective tissue underlies the palatine tonsil and forms
its capsule. The connective tissue trabeculae, some with blood
vessels arise from the capsule and pass toward the surface of
the tonsil between the lymphatic nodules