Lymph Flashcards
Effector cells of the lymphatic system
Lymphocytes
Provides physical support for lymphocytes
Supporting cells: stromal cells, monocytes/macrpphages, polymorphomuclear leukocytes, dendritic cells
Supporting cells that form a loose meshwork that creates a suitable environmetn for lymphocytes
Stromal cells
Supporting cells that assist with antigen presentation and regulation of immune response
Monocytes/macrophages, polymorphonuclear leukocytes, and dendritic cells
Non-specific type of immunity that does not require exposure to an antigen
Innate immunity
Represents innate immunity
Physical or chemical barriers, phagocytic and natural killer cells
Specific type of immunity and develops after the exposure to an entigen
Adaptive immunity
2 types of adaptive immune responses
Humoral and cell-mediated
Mediated by antibodies that act on invading agents. Produced by B cells and plasma cells
Humoral immunity
Mediated by Tc Cells, NK cells, monocytes/macrophages, PNMs
Cell-mediated immunity
Primary lymphatic organ
Bone marrow and Thymus
Type of tissue in bone marrow
Reticular connective tissue
Contents of cords of cells
Blood cell precursors, mature blood cells, adipocytes, stromal cells
General structure of bone marrow
Hemopoietic cords supported by reticular fibers
Types of stromal cells
Fibroblasts and macrophages
What does the thymus develop from?
3rd and 4th branchial pharyngeal pouch
Most abundant cell of the thymus
T cell
Supports lymphcytes that provides a framework for the developing t cells
Epithelioreticular cells
Structure of epithelioreticular cells
True epithelial cells, connected by occuding junctions and desmosomes forming a sytoreticulum, but do not decrete reticular fibers
Phagocytose the T cells that do not fulfill thymus education requirements
Macrophages
Connective tissue extends into the parenchyma as thin struts form what?
Trabeculae
Characterizes the cortex of the thymus
Densely packed lymphocytes that are the least differentiated
Characterizes the medulla of the thymus
Lighter-staining, have Hassal’s corpuscles that contain a keratin pearl
Prevents antigens from escaping cortical capillaries into the thymus cortex
Blood-thymus barrier
3 mechanisms that make up the blood-thymus barrier
Continuous capillaries (tight junctions), perivascular connective tissue (contains macrophages), Epithelioreticular cells (form occluding junctions around the capillaries)
3 stages od T cell education
Double-negative stages, Double-positive stage, single positive selection
Stage that occurs in the thymuc cortex, T cells have no CD4 or CD8, and only have CD2 and CD7 on surface
Double-negative stage
Stage that occurs in the thymic cortex, T cells express TCR, CD3, CD4 and CD8. T cells are presented with both self-MHC and self/foreign antigens and must recognize both
Double-positive stage
Stage in thymic medulla where the double-positive cells recognize self-antigen presented by self-MHC are eliminated
Single-positive stage
Secondary lymphatic organs
MALT, GALT, BALT
Lymph tissue that does not have a capsule and consists of loosely arranged immune cells
Diffuse lymphoid tissue
Spherical structures scattered throughout the lamina propria of the GI tract
Lymphoid follicles (composed mostly of B Cells)
Express receptors for soluble immunoglobins
Follicular dendritic cells
Dividing of lymphocytes are what type of follicles?
Secondary
Portion of the primary follicle that contains large, activated immature lymphocytes that are undergoing mitoses
Germinal center
Portion of primary follicle that contains small lymphocytes that arround the germinal center
Mantle
secondary lymph found in the ileum and appendix
Aggregated lymphoid follicles
Lymph in the lamina propria of the ileum
Peyer’s patches
Ring of lymph tissue at the entrance of the oropharynx
Tonsils
3 types of tonsils
Palatine, pharyngeal, smaller tonsils (lingual and tubal)
Type of tissue covering the palatine tonsils and what is forms
Non-keratinized stratified squamous epithelium that forms tonsillar crypts
Where are B and T cells stored in the tonsillar crypts?
Lymphoid follicles (B cells) and spaces between the follicles (T cells)
How do the lymphocytes exit the palatine tonsil?
High-endothelial venules
Located beneath the capsule of the lymph node
Subcapsular sinus
Projections from the lymph node capsule into the parenchyma
Trabeculae (with trabecular sinuses within them)
What cells are contained in the outer cortex of the lymph node?
B cells
What cells are contained in the paracortex of the lymph node?
T cells
Portion of the lymph node medulla that contains lymphocytes, plasma cells, macrophages, dendritic cells
Medullary cords
Recieves lymph from the trabecular sinuses and converage near the hilum where they drain into the efferent lymphatic vessel
Medullary sinuses
Allows for filtration of lymph and connects the lymphatic channels
Sinuses
Contained in the lymph sinuses
Meshwork of crisscrossing reticular fibers and macrophage processes
Drains into the efferent lymphatic vessel
Medullary sinuses
Name of the postcapillary venules in lymph nodes and what are they lined with?
High endothelial venules are lined with cuboidal epithelium
Expressed in high concentration in the HEVs
Water channels
What do the specialized endothelial cells of HEVs have?
Receptors that signal both T and B cells to leave circulation and migrate into the lymph node
Function of the lymph node
Phagocytosis and initiation of immune reponses
Where are HEV’s usually found?
T cell region
Purpose of the spleen?
Filters blood and reacts immunologically to blood-borne antigens
Contents of spleen capsule
Regular fibroblasts and myofibroblasts, so spleen can be contracted
Contents of the spleen pulp
White and red pulp
2 major components of white pulp
Periarterial lymphatic sheath (mainly T cells) and Lymphoid follicles (B cells)
Contents of red pulp
RBCs and splenic sinuses/cords
Characteristic of splenic cords
Dense meshwork of reticular fibers, large number of RBCs, macrophages, lymphocytes, plasma cells, and granulocytes. Splenic macrophages phagocytose damaged RBCs here
Receives blood that has been filtered thru the cords
Splenic sinuses
Brings blood to the spleen then breaks into trabecular arteries
Splenic artery
What artery is surrounded by PALS?
Central Artery
Short straight vessels in the red pulp
Penicillar arterioles
Arteries surrounded by a sheath of macrophages
Sheathed capillaries
Type of circulation in the spleen
Open circulation
Order of splenic veins
Splenic sinuses to pulp veins to trabecular veins to splenic veins
