Flashcards in Lymphoid Organs Deck (20):
a molecule that is recognized by our immune system. Can be soluble stuff (eg proteins, etc) or molecular (bacteria, tumors, virus infected cells, etc)
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)
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)