Lymphatics Flashcards
What is contained in the capsule of the thymus?
blood vessels
- efferent lymphatics
- no afferent. no circulation of lymphs
What does the trabecula do?
divides teh thymus into incomplete lobules. made of delicate CT
What is made of darker outer staining cortex, with an inner lighter staining cortex?
Thymus lobules.
- dark cortex: with H&E. and epithelial reticular cells, secreting thymosin.
- The blood vessels around the thymus maintain the lymphopoiesis and separate antigens.
The inner lobe of the thymus is named, and has what characteristics?
- medulla.
- allows entry of lymphocytes in blood; has no epithelial cell lining.
What are Hassall’s corpuscles
- highly keratinized medullary epithelial cell
- produce cytokine thymic stromal lymphopoietin
- –stimulates thymic dendritic cells for maturation of single positive T cells.
Double Negative T cells characteristics?
- lack surface molecules typical of mature T cells
- enter cortex from blood, proliferate in subcapsular area.
Double Positive T cells
- confront with epithelial cells at cell surface with MHC class I&II for clone selection
- express CD4 and CD8 coreceptors and TCR Receptors
Single Positive T cells
Express TCR receptors and CD4 or CD8 coreceptors.
-found in medulla of thymus
What is the Blood thymus barrier composed of?
- endothelium
- endothelial basal lamina
- perivascular space
- basal lamina of reticular cells
- reticular cells
- thymic parenchymal cells
What are the Blood Filtering Functions of the spleen?
- store/remove RBC
- convert hemoglobin to bilirubin
- fetal blood forming
- recycles Fe
What are the spleens immunologic functions?
- screen foreign material in blood
- produce lymphocytes and plasma cells
- reduces bacterial infection in children
Billroth cords form the red pulp parenchyma with what components? What do the billroth cords do?
- various cells
- terminal capillaries open directly into substance of cords
- macrophage destroy defective RBC
Venous Sinusoids of the Red pulp
- endothelial lined sinusoids with discontinuous membrane
- store RBC
- this is the closed system
Describe innate Immunity
- lack specificity and memory
- response = inflamation
- neutrophils are first responders
What is acquired immunity
- develop in response to antigen
- more powerful than innate immunity
- takes longer to develop
- displays specificity and memory
Passive Immunity
- temporary immunity due to donated antibodies
- maternal antibodies passed to fetus
Active Immunity
-long lasting permanent immunity due to self exposure to antigen resulting in memory T cell and B cell specific for that antigen.
Humoral Immunity
-an antibody mediated by plasma cells
Cell-mediated immunity
-consists of T cells and B cells and antigen presenting cells
Lymphoid Tissue has two levels of organs…?
- primary: thymus and bone marrow. contain immunocompetent cells
- secondary: lymph nodes, spleen and tonsils
Where do the lymphocytes originate?
-primary lymphoid organs and reside in secondary organs
What are the characteristics of a lymph follicle?
- no capsule
- site for B cell localization and proliferation
- are solo or aggregated
What are primary follicles?
-spheres packed with accumulations of virgin B cells and dendritic reticular cells that have not been exposed to an antigen
What are secondary follicles?
- Derive from primary follicles that have been exposed to nonself antigens
- are not present at birth