Lymphoid Tissues Flashcards
What is the role of primary lymphoid tissues?
Where lymphocytes are generated and matured
Name 4 primary lymphoid tissues
Bone Marrow Thymus Bursa of fabricating Ileal payers patch Appendix
What is the role of secondary lymphoid tissues?
Where lymphocytes interact with antigen presenting cells
Where are the 3 places secondary lymphoid tissues is found?
Lymph nodes
Mucosal associated lymphoid tissue- MALT
Spleen
Where does T cell production and maturation occur?
Produced in bone marrow transported via blood to thymus for maturation
What happens to the thymus as animals grow up?
Active in young animals, shrinks with age
What cells are contained within the thymus?
Thymocytes Mature T cells Epithelial cells Dendritic cells Hassal Corpuscles
What is found and occurs in the cortex of the thymus?
Densely populated with lymphocytes, occasional macrophages
Thymocytes mature to adult T cells then migrate to medulla
What occurs in the medulla of the thymus?
Meet antigen presented to them, thymus selection occurs, survivors become functional T cells, go into circulation and move through secondary lymphoid tissues.
What is the difference between a primary lymphoid follicle and secondary lymphoid follicle?
A secondary lymphoid follicle has a germinal centre a primary does not
What cell mostly makes up the primary/secondary lymphoid follicular space?
B cells
What is the name of the outside/internal segregational structure of a lymph node called?
Marginal sinus
What cell is present in the paracortical area of a lymph node?
T cells
What cells are present in the medullar cords of lymph nodes?
Macrophages and plasma cells
Order the following structures of a lymph node from peripheral to central: Medullary cords, paracortical, marginal sinus, primary/secondary follicle, medullary sinus
Marginal sinus, primary/secondary lymphoid follicle, paracortical, Medullary cords, Medullary sinus
What are high endothelial venues and what is their function?
Venules which allow the entery of naive cells into the lymph node to prevent them getting trapped in the afferent ducts
Describe the path of lymphocyte recirculation from tissue to return to tissue
From the tissue lymphocytes drain into fluid into the afferent lymph to the lymph node, they then pass into the efferent lymph leaving the lymph node, and enter blood circulation via the thoracic duct which intern will lead back to tissue. While circulating lymphocytes may detour through the spleen of HEVs to return to lymphoid tissue
What is a germinal centre?
A cluster of proliferating lymphocytes in response to antigen
Why do lymph node enlarge?
When antigen in encountered lymphocytes activate and proliferate forming a germinal centre and causes the lymph node to enlarge
What is the function of lymphatic fluid?
Drains and removes interstitial fluid, transports dietary lipids and facilitates immune responses by draining antigens from tissues and eventually the blood
What is red pulp/white pulp in the spleen?
Red Pulp- Open sinusoids containing RBCs- reservoir
White Pulp- Contains mainly lymphocytes- compartmentalised into T/B segments
What does PALS stand for?
Peri-arteriolar lymphatic sheath
What creates the spleens framework and structure?
The continuous capsular connective tissue that forms the capsule and trabeculae
What is PALs?
Splenic T cells which are closely associated with arteriolar blood vessels which form a cylindrical surrounding
Where are B cells found in the spleen?
Within the primary/secondary follicles adjacent to PALs
What surround the PALs and primary/secondary follicles in the spleen?
Marginal Zone
What is MALT?
Mucosa associated lymphoid tissues
What are examples of MALT?
GALT- gastrointestinal
BALT- bronchial
NALT- nasal
CALT- conjuntiva
What comprises of a Peyer’s patch?
Uncapsulated lymphoid aggregate- comprising of a series of B cell follicles surrounded by intervening zone of T cells
