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20 Cards in this Set
- Front
- Back
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What are primary (central) lymphoid tissues? In humans, what are these organs?
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Where lymphocytes develop and mature into immunocompetent cells. Fetal liver, bone marrow, thymus. Fetal liver can even produce some cells.
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What are secondary (peripheral) lymphoid organs? In humans, what are these organs?
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Environment where immunocompetent cells can react with each other, antigens, other cells to mount an immunological challenge against invading pathogens/antigens.
Humans: lymph nodes, spleen, MALT, postnatal bone marrow |
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Is bone marrow a primary or secondary lymphoid organ?
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BOTH. It's special, our one big source of "stem like" cells that can differentiate.
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Thymus: is it a primary or secondary lymphoid organ? What happens there? Where is it located? What does it look like? What does it arise from? Where do T lymphocytes arise from?
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Primary, T lymphocytes mature here. Superior mediastinum, over great vessels of heart. Small encapsulated organ made of two LOBES. Arises from 3rd, possibly 4th pharyngeal pouches of embryo. T lymphocytes arise from mesoderm.
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Describe the development of the thymus, starting from embryo.
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Originates early in embryo, grows until puberty where it may weigh as much as 35-40 g. After first few years of life, INVOLUTES (atrophies) and infiltrated by adipose cells, but may continue to function in some adults.
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How can you differentiate between the cortex and medulla of the thymus?
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Cortex - very compact/dense, has lymphocytes/developing thymocytes.
Medulla - sparse, see stromal elements. |
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What is the key to identifying the medulla of the thymus histologically?
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Hassall's corpuscle.
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What is the thymus surrounded by?
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Delicate NO FIBROUS capsule, with no CT stroma in it.
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What kind of cells make up the cortex of the thymus?
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1) 3 types of epithelioreticular cells (probably derived from pouch endothelium)
Type 1 - separates cortex from CT cpaulse and trabeculae, completely isolates cortex from the rest of the body - tight junctions Type 2 - midcortex, desmosomes - more supportive framework Type 3 - deep cortex at C-M boundary - isolates cortex from medulla, tight junctions 2) APCs - bone marrow derived interdigitating cells, present self antigens, MHC I and MCH II molecules to developing T cells 3) Tingible body macrophages - phoagcytize 98% of developing T cells that die in the cortex |
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What kind of cells make up the medulla of the thymus?
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ERC :
Type 4 - associated with type 3 at C-M boundary, assist with C-M junction Type 5 - cytoreticulum of medulla - stromal support framework where other cells reside Type 6 - form Hassall's Corpuscles - most characteristic identifying feature in organ |
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What is the vascular supply of the thymus?
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Blood thymus barrier - important "incubator" b/c we are developing unprogrammed cells that haven't experienced any antigenic material.
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What is so special about the lymph node?
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It's the only structure that has an afferent lymphatic supply! Lymph flows in and out of it. Everything else, lymph flows out. Its sole purpose is filtering lymph.
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What is the lymph node divided into? What are the two types of nodules?
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Outer cortex, inner medullary region. Primary - accumulation of lymph not doing anything. Secondary - B cells turning into plasma cells.
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Map the flow of lymph through a lymph node.
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Afferently from all points on the capsule -> sinuses in cortical area (where lymph nodes are) -> medullary region (lymphatic sinuses where all are draining to) -> efferently
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How does the medullary region of the cortex of the lymph node compare to the cortex?
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Very spacious, most of the empty area is sinus - where all the stuff is filtering down after it's come into contact w/ cells in the cortical region.
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What are germinal centers?
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Secondary lymphatic nodules. Group of lymphocytes that haven't been exposed to anything. They all look alike, but if you throw an antigen in, some cells will differentiate due to the antigen.
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How do you differentiate the spleen from the lymph node from th thymus?
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Thymus = Hassall's corpuscle
Lymph node = bean shaped, can see cortex and medulla Spleen = has NO cortex or medulla, has RED PULP and RIGHT PULP, look for center arteriole (small artery in center of core of white pulp). Adventitia has been replaced by lymphocytes of white pulp. |
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What is PALS?
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Peri Arterial Lymphoid Sheath
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What are MALT/GALT/BALT?
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MALT - mucosal associated lymphoid tissue (all accumulations of lymphoid tissue that lie under epithelium
GALT - Gut Balt - Bronchial |
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Tonsil is an example of which -ALT? What is it and what are the two different types and what kind of epithelium are they under?
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GALT.
**Accumulation of lymphoid tissue that lie under an epithelium** Palatine tonsil is under stratified squamous (probably keratinized) Pharyngeal tonsil is under pseudostratified squamous |
