Lymphoid Flashcards
Central (primary) lymphoid organs
Bone marrow
thymus
Peripheral (secondary) lymphoid organs
lymph nodes
spleen
tonsils
Peyer’s patches
Lymphocytes are supported by
Reticular fibers (type 3 collagen)
myeloid tissue
(A type of reticular tissue) - free cells are developing erythrocytes and granular leukocytes (bone marrow)
Most reticular cells are of _________ origin
mesenchymal
Functions of Reticular cells
synthesis and maintenance of ECM, Phagocytosis, Storage of Ferritin; Antigen processing/presentation
Nodular lymphoid tissue looks like
compact, spherical, lack a ‘c.t.’ capsule; mostly B lymphocytes
T or F
Lymphoid nodules are limited to lymphoid organs
FALSE
Germinal centers contain
activated B lymphocytes; appear during primary antigenic response
Lymph cortex is composed of:
Loose lymphoid tissue: subcapsular/peritrabecular sinuses
Lymphatic nodules: primary or secondary (mostly B lymphocytes)
Components of Medulla:
dense lymphoid tissue: medullary cords (B and plasma cells)
loose lymphoid tissue: medullary sinuses (reticular cells)
Flow of lymph:
1) Afferent lymphatic
2) subcapsular sinus
3) trabecular sinus
4) medullary sinus
5) efferent lymphatic vessel
The medulla of a lymph node:
facilitates the filtering function of the nodes
Key molecules in Lymphocyte Homing
selectins, integrins, carbohydrates (sugars and mucins), Ig superfamily members (ICAM, VCAM), clever1
Medical relevance of HEVs
lymphocyte recirculation (contribute to specificity), implicated in metastasis of lymphomas; located btwn cortex and medulla
Thymus
develops from epithelial lining of 3rd and 4th brachial pouches; full size by first year of life
Cell types within thymus
Thymocytes, Epithelial reticular cells, Mesenchymal reticular cells
Epithelial reticular cells:
help form Hassall’s corpuscles, are involved with secretions, provide framework (cytoreticulum) and contribute to blood-thymus barrier
Mesenchymal reticular cells looks like:
black blobs! (loaded with garbage b/c they are phagocytic)
Thymus cortex v. medulla
cortex: thymocytes v. medulla: epithelial reticular
Functions of Thymus
development of diverse population of T lymphocytes that can respond to foreign antigens (thymosin)
trophic role in the development of other lymphoid organs (thymopoietin)
Function of tonsils
Detection and response to pathogens in oral cavity and production of lymphocytes
Functions of the Spleen
production of lymphocytes, immune response to blood bourne antigens, destruction of old RBCs, resevoir of monocytes and storage of blood
