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Flashcards in Lymphoid Organs Deck (20):

define: antigen

a molecule that is recognized by our immune system. Can be soluble stuff (eg proteins, etc) or molecular (bacteria, tumors, virus infected cells, etc)


define: opsonization

covering something in antigens/opsonins will stimulate/enhance its phagocytosis


define: lymphoid tissue

tissue which produces immune cells


where is lymphoid tissue found (5)

MALT (mucosa associated lymphoid tissue) which is colonies of lymphoid tissue dispersed in mucosa/submucosa round body (TONSILS + PEYER'S PATCHES)



SPLEEN (largest colony of lymphoid tissue in body)

lymphatic vessels (eg thoracic duct)


what does MALT look like histologically?

a large, dark staining blob w/ v thin CT capsule


what can you find inside MALT tissue? (4)

lymphocytes (mostly B cells)
plasma cells (immature B cells which secrete IgA)
APCs (lymphocytes, dendritic cells, macrophages)
reticular fibres


What is an example of MALT? (Peyer's patches in ileum). Describe the components of the epithelium of the ileum where you would find a Peyer's Patch (4)

simple columnar ilium epithelium, goblet cells, underlying Peyer's Patch (which includes lymphocytes + microfold (M) cells)

M cells are large, oblong, paleish purple cells
lymphocytes are round, spotty cells


What is the thymus? (childhood lymphoepithelial organ). What is its embryonic origine (hard bonus question)

mesenchymal + epithelial primordium


what does a thymus look like

dark, bluish blob with a lighter core (dark cortex + lighter medulla).

has CT capsule which forms incomlete lobules (looks like corn pops)


what is in the dark outer cortex of a thymus lobule? What is in the light medulla?

cortex: undifferentiated T cel precursors, macrophages + epithelial reticular cells (kills T cells that self recognize body's own proteins)

medulla: epithelial reticular cells, mature T cells (CD4 + CD8), and HASSAL'S/THYMIC CORPUSCLES (looks like a dark pink onion, no known function))


note: epithelial reticular cells look like pale fried eggs with a too small, centrally located yolk



lymph node - describe the macrostructure (afferent lymph vessels --> efferent lymph vessels

afferent lymph vessels --> into greater curvature of lymph node --> out lesser curvature as efferent lymph vessels


describe the layers of a lymph node

covered by a thin CT capsule

paracortical region (outer cortex + inner cortex), contains LYMPHOID NODULES

medulla contains MEDULLARY CORDS (B cells) + MEDULLARY SINUSES

(looks like pink chords and white spaces


what is so special about the spleen? (largest collection of lymphoid tissue in the body + has lots of PHAGOCYTES to munch old RBCs)



what is the role of the spleen?

to munch old RBCs and tho make antibodies


histology of the spleen

dark red CT capsule w/ trabecular


white pulp (actually looks blue/purple )

(PALS + marginal zone sinuses + central artery + lymphoid nodule)

red pulp (actually looks white/pink)


The spleen has both closed and open circulation. Describe the closed circulation

Closed : Blood comes in central artery, passes into penicillar arteriole, and directly into a sinusoid and then leaves the lymph
• Open: blood comes in via central artery, through penicillar arteriole, and those arterioles do not terminate in a sinusoid
• Material has to filter through red pulp before getting to sheath
• Allows for recycling of RBCs - red pulp destroys and then renews old RBCs

closed circulation: blood --> central artery --> penicillar arteriole --> sinusoid--> trabecular vein


the spleen has both closed and open circulation. Describe the open circulation

blood comes in through a central artery --> penicillar arteriole --> leaks into open circulation (random spot in red pulp) before being picked up by a sinusoid and drained into a trabecular vein.

Advantage: blood gets filtered through red pulp. Can break down old RBCs.


where is and what is PALS?

Periarterial lymphatic sheath. White pulp found around central artery of the spleen, containing T cells. PALS is surrounded by marginal zone sinuses (not req'd to ID on bellringer)


what are biliroth's chrods?

aka splenic cords. Cords of lymphatic tissue (lymphocytes B and T cells, macrophages, plasma cells + blood cells), looks like a pink chord running through the white pulp. Sinuses look white.