Organs of the immune system Flashcards
What organs are apart of the central lymphoid tissues?
Bone marrow
Thymus
Fetal Liver
What organs are apart of peripheral lymphoid tissues?
Lymph nodes
Spleen
Mucosa-associated lymphoid tissues
What is the function of the primary lymphoid tissues?
Nurture lymphocyte development
What are the functions of the secondary lymphoid organs?
Support lymphocyte maturation, survival and activation
Drain antigenic material from tissues and organs
Internal lymphoid organs
Thymus
Bone marrow
Spleen
Lymph nodes
Surface lymphoid organs
Respiratory tract
Mammary glands
Salivary glands
Intestine
Urogenital system
What are the sources of lymphocytes?
Yolk sac, fetal liver and bone marrow
What are the sites of lymphocyte development?
Thymus
Bursa
Peyer’s Patches
Bone marrow
What are the sites where lymphocytes respond to antigens?
Tonsils
Spleen
LN
PPs
Bone marrow
Where are all immune cells derived from?
Bone marrow stem cells
Thymus
Cranial mediastinal space (thorax)
First lymphoid organ to develop in fetus
Bilobed organ
Where is the thymus size the greatest?
@ puberty, involution occurs slowly
What does the outer cortex and inner medulla of the thymus have?
Cortex: immature proliferating lymphoid cells (thymocytes)
Medulla: Mature T cells
Thymic epithelial cells
Produce trophic hormone, thymosin-a, thymopoietin, thymulin and thymus humoral factor that play a role in T cell maturation
Pos. and neg. selection of T cells
Pos: T cells with receptors with intermediate affinities
Neg: auto reactive T cells (recognize self antigens)
Fewer than ________ of thymocytes leave the thymus
5%
Thymic involution
Physiologic, age-associated decrease of cellularity
Thymic Atropy
Stress/ pathological conditions (increase in corticosteroids)
What are the major functions of LNs
- Trap antigens
- Provide organized area for antigen presentation
- Provide signals to maintain lymphocyte survival
- Site of initiation of adaptive response
- Lymphocytes cross into lymphatics from the blood by interacting with specialized endothelia called HEVs
How is the LN organized?
Outer cortex and inner medulla (pig is reversed)
Outer cortex of the LN
Aggregates of B cells with primary and secondary follicles (germinal center)
Paracortex of the LN
Contains mainly T cells
Medulla of the LN
Cord: B cells, plasma cells, macrophages
Sinuses: Lymph, macrophages, granulocytes, deliver lymph to efferent lymph vessel
What is the function of the spleen?
To filter blood
Remove antigens and old RBCs
Cells can enter and leave by bloodstream
