Learn about Secondary lymphoid organs in humans with details. Lymphoid organs are site where cells of immune system originate and develops and where acquire immune responses are initiated. for more such content contact me at faunafondness.com

1. SECONDARY LYMPHOID
ORGANS
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2. LYMPHOID ORGANS
• LYMPHOID ORGANS ARE SITE
WHERE CELLS OF IMMUNE
SYSTEM ORIGINATE AND
DEVELOPS AND WHERE
ACQUIRE IMMUNE RESPONSES
ARE INITIATED.
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3. Lymphoid organs
Primary lymphoid
organs
Thymus
Bone marrow
Secondary
lymphoid organs
Lymph nodes
Spleen
M.A.L.T.
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4. SECONDARY LYMPHOID ORGANS
•These organs provide the sites for the interaction of
lymphocytes with the antigen, which then proliferate to become
effector cells.
•These are of following types:
•(a) Spleen
•(b) Lymph nodes
•(c) Mucosal associated Lymphoid Tissue (MALT)
•Peyer’s patches of small intestine and appendix are also some of
the secondary lymphoid organs.
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5. Secondary lymphoid tissues functions as filtration devices removing
•Dead cells
•Foreign matter
•Protein aggregates from the circulation.
Secondary lymphoid organs are rich in supply of blood vessels and lymphatic vessels
these facilitates the movement of lymphocytes, monocytes and dendritic cells into and
out of these organs.
Antibodies are formed in secondary lymphoid organs.
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6. Lymph nodes
Small round or oval shaped secondary
lymphoid organs.
Function as filter to purify lymph,the fluid and
cellular content of the lymphatic circulatory
system.
provide site for lymphocytes,monocytes and
dendritic cells for initiation of immune
resposes
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7. Cortex
Paracortex
Medulla
• Outer most layer
• Contains lymphocytes,macrophages
follicular dendritic cells arranged in
primary follicle.
• Contains T lymphocytes
• Thymus dependent area.
• Inner most layer
• Contain blood vessels
STRUCTURE
OF LYMPH
NODES
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9. Phagocytosis of antigen
B cells differentiate into plasma cells
Initiation activation of B cells take place within Para cortex
Activation of B cells
Resulting activation of T cells.
MHC molecules-Atigen(interdigitating dendritic cells)
It is trapped
Antigen reaches at regional node(lymph)
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10. Spleen
•Bean shaped organ.
•Present in left side of abdominal cavity.
•Specializes in filtering blood and trapping
blood borne antigens.
•Blood borne antigens,lymphocytes through
splenic artery.
•Spleen surrounded by capsule.
•Also contains large numbers of plasma cells
secreting immunoglobulins into the
circulation.
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11. •Network of sinusoids
macrophages,RBC,lymphoc
ytes.
•Old and defective RBC
destroy.
RED
pulp
•Consists of lymphoid
tissues, T and B
lymphocytes.
•White pulps surrounds
branches of splenic artery
forming Per arteriolar
lymphoid
sheath(PALS)
White
pulp
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12. Plasma cells-antibody production
Rapidly dividing B cells
Activation of B cells
Combined with MHC molecules and T helper cells
Initial activation of B and T cells in PALS
Trapped by interdigiting dendritic cells
Blood borne antigen and lymphocytes(splenic artery)
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13. Mucosa-associated lymphoid tissue(MALT)
•This is located within the lining of main tracts in the
body like respiratory, digestive, urogenital tracts.
•MALT is populated by lymphocytes such as T
cells and B cells, as well as plasma
cells and macrophages, each of which is well
situated to encounter antigens passing through the
mucosal epithelium.
•The secondary lymphoid tissues that defends the
mucosa surfaces are:-
•Tonsils in the nasopharynx.
•Peyer’s patches in the submucosal surfaces of the
small intestine
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14. Tonsils
•Tonsils are located as a
defensive ring around
the nasopharynx at the
port of entry for both the
respiratory and
gastrointestinal systems.
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15. Peyer’s patches
•Peyer’s patches are
lymphoid accumulation
lying underneath the villi
of small bowel(within the
area delineated by the
dotted line).
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16. Intestinal villi
• Intestinal villi contain
intraepithelial
lymphovytes,interstitial
leukocytes and raining
lymphocytic(lacteals) that
serve to both sample the
intestitial environment
and defend the bowel
from bicrobial invasion.
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17. Interact with antigen
Secretary IgA into lumen
Transported across epithelial cells
Secrete IgA class of antibodies
Differentiate into plasma cells
Activated B cells in follicle
Antigen transported across mucous membrane by M cells
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18. Conclusion
•Secondary lymphoid organs (SLOs) include
lymph nodes, spleen, Peyer's patches, and
mucosal tissues such as the nasal-associated
lymphoid tissue such as tonsils.All SLOs serve
to generate immune responses and
tolerance.SLOs are very important as they
provide sites for the interaction of
lymphocytes with the antigen, which then
proliferate to become effector cells.
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19. References
•Immunogy by P.M.lydyard, A.Whelan
and M.W.Fanger
•Essential of immunology by S.K Gupta
•Kuby immunology by Stanford,
jones,owen
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