Lymphatic System Flashcards
What is the morphology of lymph capillaries?
-large lumen, no pericytes, incomplete basement membranes and incomplete endothelial junctions
What is the morphology of lymph vessels?
layers indiscrete
- intima: endothelium, few elastic fibers
- media: can be 1-2 smooth muscle layers
- adventitia: blends into surrounding connective tissue
- valves: movement of tissue and muscle causes lymph to move one way.
What is red pulp made of? How can the meshwork be described as?
made up of splenic sinuses (venous sinuses) separated by splenic cord (cords of billroth) .
-meshwork: reticular cells, and fibers, lymphocytes, plasma cells, and granulocytes
Which major organ detects antigens in the blood?
spleen
describe the role of red pulp.
- filter RBCs
- phagocytize dead, dying RBCS or incapable of transversing the microcirculation of the spleen.
- RBC reservoir
What do monocyte/macrophage system make up?
includes blood monocytes, alveolar macrophages, splenic macrophages, lymph node macrophages, and dendritic macrophages, microglia, kupffer cells, intraglomerular mesangium of kidney, serosal macrophages and langerhans cells of skin
How do macrophages interact with lymphocytes?
- macrophages are necessary for lymphocyte survival (tropic factors)
- lymphocytes activate macrophages
- macrophages (APC) process and present antigens to lymphocytes
lymphatic system can be subdivided into
functionality (t and b cells) or histologically (tissue, organs and vessels)
T cells produce substances that mediate their function in 4 ways:
- attraction and activation of macrophages.
- delayed hypersensitivity (graft rejection)
- cytolytic activity (tumor immunity)
- contact activation (poison ivy)
Give the three major subdivisons of t-cells. Describe its general function and cytokines.
- Helper cells (TH): promote and activate other immune cells, stimulate b-cell. express CD4
- Suppressor cells (TS): suppresses B cells, macrophages. CD4
- Cytotoxic lymphocytes: (TC,killer T-cells): kills target cells, such as virus-infected cells, tumor cells, and transplanted cells (grafts) CD8
MHC1 where is it found. what is its function?
found on all nucleated cells and platelets.
- allow the elimination of abnormal host cells (virus-infected or transformed cancer cells)
- present peptides to KILLER T-CELLS
- transformed cells display viral or cancer specific peptides (recognize as non-self).
- all endogenous “self peptides” display on normal cells in body.
MHC 2 expressed where and what type of peptides does it present?
expressed on surface of all APCs only
-present partially digested, endocytosed foreign peptides to helper t-cells.
What system is responsible for antibody synthesis and release? How is it activated?
humoral immunity and b cells produce antibodies.
-interleukins produced by T-cells
What are null cells (natural killer cells)? What are they generally found?
Doesn’t need to be exposed to antigen in order to be cytotoxic.
- can recognize transformed cells such as tumor cells and virus infected cells.
- most are in tissue
lymph from most sites is returned to ___, which empties into __. lymph from right side of head head empties into __duct, which empties into ___.
thoracic duct; left subclavian vein.
-right lymphatic duct into right subclavian vein
GALT
gut associated lymphoid organ collects antigens from the epithelial surface of GI tract.
once tagged what type of cells kill the cell?
macrophages, neutrophils, eosinophils, natural killer cells.
how do mast cells react to antigen presenting cell?
degranulation by releasing of histamine and heparin.
Degranulation causes what in each of these regions. (gut, lung, tissue)
gut: causes diarrhea and vomiting
lung: increase in mucus secretion and bronchial contraction leading to coughing.
tissue: increase in Blood flow, lymph flow and increase in permeability.
What are the markers for helper t cells, killer t-cells , suppressor b-cells and plasma cells?
TH: CD4
TS: CD4
TC: CD8
plasma: CD20
Where do B cells settle in?
bone marrow or lymphoid tissue to secrete antibodies.
Antibodies cannot tag pathogens that are inside cells. So, what type of cells is needed?
T-cells, antibodies can attack pathogens as they enter the body
What are the two organs that make the central lymphoid tissue ad describe the general components?
- Bone marrow: lymphoid stem cells
- thymus: contains microenvironment and hormones necessary to develop IMMATURE lymphoid cells into B and T-cells.
site of maturation of cells in the immune system
-doesn’t react to antigens
Peripheral lymphoid tissue includes:
- lymph nodes
- part of spleen
- lymphatic aggregates- in gut, respiratory tract
- diffuse lymphoid tissue- in gut, respiratory tract.
- react to antigen
B cells and T cells populate in specific areas of peripheral lymphoid tissue. Where are each of these locations?
- In lymph node: T cells go to deep cortex (paracortex)
- b cells go to germinal center of nodules and medulla of lymph nodes
In Fever, how do immune cells induce elevation in body temperature. What medication is used to block prostaglandins?
- immune cells release IL-1 (pyrogen acting) –> formation of prostaglandins
- aspirin (antipyretic) blocks prostaglandin formation.
thymic function
- antigen independent lymphocyte production and differentiation
- transformation of immature lymphocyte into immunocompetant T lymphocytes
- colonization of peripheral lymphatic tissue with t lymphocytes (leave thymus to go to other lymph organs)
DiGeorge Syndrome
congenital absence or hypoplasia of thymus or parathyroid glands
- associated with abnormal cell-mediated immunity but relatively normal humoral immunity.
- low Ca2+ levels in blood.
What is the general histology of thymus?
made of two lobes, encased in capsule, with numerous lobules
Thymocytes
lymphocytes on cortex, as they undergoe differentiation, migrate towards medulla- most die via apoptosis
Blood-thymus barrier. what is it surrounded by and how does it protect the thymic cortex?
thymic capillares are continuous and surrounded by epithelial reticular cells-prevents foreign antigens from entering the thymic cortex and reaching developing t-cells.
reticular epithelial cells. What are they connected to each other by and what type of support?
connected by desmosomes and tonofilaments
-provide support, isolation, and produce trophic hormones that stimulate T-cel maturation (thymosin)
Thymic macrophages
form boundary at inner cortex- remove defective T cells as they move towards the medulla.
How are macrophages and dendritic cells involved with thymocytes?
present self-antigens to thymocytes.
Medulla consists of
contains immunocompetent t-cells (can distingusih self from non-self)
- foreign dendritic cells (don’t phagocytize foreign material, just stick to cell membrane)
- hassals corpuscles (concentric thymic reticular cells
Where can diffuse lymphoid tissue be found? and what does it contain?
found within connective tissue- more common in GI (GALT) and respiratory tract (BALT).
contains:
- macrophages, lymphocytes, plasma cells
- lymph capillaries
- collagen and reticular fibers, cells
lymphoid nodules
-sphere of lymphocytes (mostly B lymphocytes) packed together, often located in GI, respiratory, and urinary tacts.
What is the difference between primary and secondary nodules
primary nodules (inactive) lack a germinal center; have not been exposed to antigen.
-2nd: active contain germinal center where proliferating lymphoblasts, plasma cells, macrophages and reticular epithelial cells are and mantle zone where inactive b cells .
Where can lymphatic nodules found?
in peyer’s patches (in ileum of small intestine.
-nodules can also be found in appendix and tonsils.
lymph nodes
encapsulated organs containing multiple lymphoid nodules .
function: filter lymph and concentrate foreign material (macrophages ingest foreign material and present the antigen to lymphocytes- APC
Where are B and t cells located in the cortex of lymph node
B-cells: outer cortex in nodules
t-cells: predominated the paracortical area.
Describe the general structure and function of capsule of lymph node.
capsule: dense CT- subcapsular space receives lymph.
What are the APC cells
neutrophils, macrophages, b-cells, and dendritic cells
the cortex contain secondary nodules with
proliferating b cells, resident follicular dendritic cells, migrating dendritic cells, macrophages, and supporting reticular cellls.
WHere are FDCs found, what type of processes do they have? And why aren’t they considered APC?
found in germinal centers of lymph nodes.
- have thin processes that interdigitate with b cells
- b/c they don’t endocytose foreign matter and present it on MHC 2 receptor
Paracortex contains what types pf venules? and what is their role?
postcapillary (high endothelial) have cubodial endothelium which allows lymphocytes to pass through their walls to enter/ exit the lymphnode.
-houes t cells
Diapedesis
movement of cells in and out of blood vessels
Medulla of lymph node consists of primary __ cells.
B
Where do the major blood vessels enter and exit?
Hilus
stroma is made of what? what do reticular cells produce?
collagen and reticular portions..
- produce reticular fibers
What are the 2 major functions of spleen?
blood filter: able to phagocytize RBCS, RBC reservoir
-lymphoid organ: respond to blood borne antigens.
Histology of Spleen
tracbeculae, capsule
-parenchyma: white and red pulp
White pulp
follows blood vessels
- diffuse lymphoid vessel
- lymphoid nodules
- central artery
- periarterial lymphatic sheath (PALS): sheath of concentrated T cells surrounding a central artery
What are the primary and secondary lymphoid organs?
primary: thymus and bone marrow
secondary: lymph node, lymph nodules and spleen
