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Lymphatic System Histology
Terms in this set (44)
List the cells of the lymphatic system
Lymphocytes (B, T, NK cells) and APCs (macrophages)
Bone marrow derived
Present antigens to lymphocytes (weakly)
Endocytose and partially degrade antigens for presentation
Digest pathogens via lysosomes
Name the 3 types of cytokines that macrophages can produce.
Lymphokines, complement proteins, interleukins
How to antigen presenting cells (APCs) work?
Phagocytose macromolecules and process them
Peptides bind to MHC
Antigen-MHC complex goes to surface of the cell
Complex is displayed to helper T cells
Describe the organization and function of supporting cells of the lymphatic system.
Organized in loose meshworks
Reticular cells live here and produce reticular fibers
Lymphocytes and other cells live here too
Types of cells identified by CD (clusters of differentiation) molecules
List the primary lymphoid organs.
Bone marrow (all lineages)
Thymus (T cell maturation)
List the secondary lymphoid organs.
Diffuse lymphatic tissue
List the characteristics of lymph vessels.
Contain no RBCs
Run alongside blood vessels
Describe the path of immune cell circulation.
Bone marrow -> body tissues -> lymphatic tissue -> bone marrow
Where can you find diffuse lymphoid tissue?
GALT (lamina propria/submucosa), BALT, GU tract
Is diffuse lymphoid tissue encapsulated?
After diffuse lymphoid tissue comes in contact with a foreign substance/invader, where does it go and what does it do?
It travels to a lymph node where it proliferates and differentiates. Progeny return to site of origin as effector B and T cells.
Secrete antibodies onto lumen
Concentration of lymphocytes in meshwork of reticular cells and fibers
Are lymphoid nodules encapsulated?
What do primary nodules contain?
What do secondary nodules contain?
Germinal center - large immature lymphocytes, B cells, follicular dendritic cells
Mantle zone - small lymphocytes
Where are lymphoid nodules located?
Tonsils, Peyer's patches, appendix, MALT
What is the function of lymph nodes and where are they located?
Filter out lymph
Located along path of lymph vessels
Are lymph nodes encapsulated?
What 2 types of vessels do lymph nodes have? Do they act as entrances or exits? Where are the blood vessels location in relation to these?
Afferent vessels - enter convex surface
Efferent vessels - exit at hilum, blood vessels enter and leave here
Name the 3 layers of a lymph node.
What is located in the cortex of the lymph node?
Primary follicle - aggregates of B cells
Secondary follicle - germinal centers in response to antigen stimulation which cause lymphoblast proliferation
What is located in the paracortex of the lymph node?
Helper T cells
High endothelial venules
Acts as site of B and T cell entry to lymph node 90% of the time
What is located in the medulla of the lymph node?
Sinuses surrounded by macrophages and reticular cells
What types of immune cells make up the medullary cords?
B cells, macrophages, plasma cells
List the steps an antigen or antigen-antibody complex takes through the lymphatic system to reach a lymph node.
1. Lymph carries Ag or Ag-Ab complex to sinuses
2. Get picked up by APCs or percolate into follicles
3. B cells are activated
Plasma cells go to medullary cords to secrete Ab.
Memory cells circulate the tissues and wait to be restimulated
Secrete type III collagen to form stroma of meshwork
Anchored to meshwork by cytoplasmic processes
Secrete trophic cytokines
What do trophic cytokines produced by the reticular cells of the reticular meshwork do?
Attract T, B and dendritic cells
Bone marrow derived
APCs - MHC I and II
Circulate from tissue to lymph node via the blood
Located in T cell rich areas
Follicular dendritic cells
Non-migratory, stay in follicles of lymph node
MHC I cells that persist for years
What occurs in the thymus?
T cell maturation
What does the thymus attract?
What does the cortex of the thymus contain and what occurs there?
Epithelial reticular cells
Most T cell development occurs here
Epithelial reticular cells
Isolate and contain thymic domains
Surround vascular elements
Present self-antigens, MHC I and II molecules
What is contained in the medulla of the thymus?
Thymocytes here are mature, immunocompetent T cells
Type VI epithelial reticular cells
What is the function of the spleen?
Filters blood and reacts immunologically to blood-borne antigens
What types of cells are contained in the red pulp and what is its function?
Removes senescent and damaged RBCs
Reservoir of RBCs
Sinusoids with rod-shaped epithelial cells separated by cords of Bilroth
What is contained in the white pulp and what is its function?
Thick sleeve of lymph around an artery
Immune component of the spleen (contains T and B cells, macrophages)
Closed circulation theory of the spleen
RBCs are dumped into the splenic sinus where damaged ones are picked up by macrophages which can reach through spaces in the lining of the sinus.
Open circulation theory of the spleen
RBCs reach the end of terminal arterial capillaries and are dumped into open space
How are senescent RBCs broken down by the spleen?
Surface molecules of the RBC degrade over time and biconcave shape becomes compromised
Phagocytized by macrophages
What is the fate of hemoglobin after an RBC is destroyed by the spleen?
Globulins break down and circulate as amino acids
Heme is converted to bilirubin and then to bile
Iron is moved to the bone marrow for reuse
This set is often in folders with...
Amino Acid Anabolism
Carbohydrate Metabolism 2
Fundamentals of Immunology I
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