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Objective
Structure and functions of the primary andsecondary lymphatic organs and lymphatictissues
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LYMPHATIC QRGANS & TISSUES
-Primary lymphatic organs :
Thymus, bone marrow
- Secondary lymphatic organs & tissues
Spleen, lymph nodes, tonsils,
lymph nodules/MALTs
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The distribution of lymphatic organs
and vessels
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Components lymphatic tissue :
1. Reticular fibers
2. Mesenchymal reticular cells
3. Epithelial reticular cells
4. Lymphocytes : T and B lymphocytes,Plasma cells
5. Macrophages
6. Antigen presenting cells
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Immunity reaction :
1. Cellular (cell-mediated) immunity : T lymphocytes
2. Humoral immunity : IgG, IgA, IgM, IgE and IgD
(antibodies)
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Origin of the main type of
lymphocytes
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The thymus is a central /primary lymphatic
organ situated in the mediastinum at about
the level of great vessels of the heart.
Structure :
Lobe
Lobules :
1. Cortex : small lymphocyte, epithelial reticular cell
and blood-thymus barrier.
2. Medulla : - Hassalls corpuscles
- Extend into the core of each of the
lobules
THYMUS
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Thymus
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Desmosome
Desmosome
Desmosome
Epithelialreticular cell
Lymphocytes
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Histogenesis and involution :
Third pharyngeal pouches (endodermal)
Functions :
1. T-lymphocytes production
2. Hormone production : thymopoietin, thymosin
3. Blood-thymus barrier
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Lymph nodes are encapsulated sphericalor kidney-shaped organ composed of
lymphoid tissue.
Scattered in group along lymphatic vessels in
the neck, axilla, groin, thorax and abdomen,
they act as in-line filter of the lymph,
removing antigen and cellular debris and
adding Ig.
LYMPH NODES
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1. Pericapsular fat andconnective tissue
2. Capsule
3. Lymphatic tissue
4. Capsule andafferent lymphatics
5. Cortex
6. Medulla
7. Trabeculae
8. Blood vesselsin trabeculae
9. Marginal(subcapsular)
sinus
10. Arterioles11. Efferentlymphatic vessels
12. Hilus
13. Medullarysinuses
14. Medullary cords
15. Cortical nodules(Lymphatic nodules)
16. Marginal(subcapsular) sinus
17. Germinal centers
18. Veins
LYMPH NODE (PANORAMIC VIEW)
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Structure :
Cortex :
The dark-staining owing to presence of tightly packed
lymphocytes.
Secondary lymphoid nodules (containing primarily Blymphocytes) with germinal centers.
Medulla :
Lighter staining than cortex.
Composed of cords of lymphoid tissue
(medullary cord)
separated by medullary sinuses.
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Paracortical zone :
This is the T-dependent region, lying
between the cortical lymphoid nodules
and the medulla.
Characteristized by the presence ofmany high-endothelial post capillary
venules.
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Lymphatic Vessels : Afferent lymphatic vessels
Efferent lymphatic vessels
Afferent vessels subcapsular sinusperitrabecular sinus
medullary sinuses
efferent vessels
exiting through the hilum
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Function :- Filtration of lymph
- Lymphocyte production (lymphopoiesis)
- Immunoglobulin production
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Spleen, the largest of the lymphoid organ, lies
in the upper left quadrant of the abdominal
cavity. It serves as the immunologic filter of
the blood.
SPLEEN
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7. Germinal center
8. Tangentialsection of asplenic nodule
9. Central arteries(t.s) in splenicnodules
10. Venoussinuses in thered pulp
11. Trabecularveins
12. Trabeculae (t.s)
13. Sheathed artery14. Pulp arteries(arterioles)
1. Peritoneumand capsule
2. Splenic nodules(white pulp)
3. Trabeculae
4. Trabecularartery
5. Splenic cords inthe red pulp
6. Central artery(l.s)
SPLEEN
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Structure :
Splenic pulp :White pu lp
- Central artery- Periarterial lymphatic sheaths (PALS) :
Tdependent region
- Peripheral white pulp (PWP) :
B lymphocytesRed pulp
- Red pulp cords (Billroths)
- Splenic sinusoid
The marginal zone :- Border between
the white and red pulp
- Marginal sinuses
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Schematic view of blood circulation
of the spleen
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Splenic circulation :
a. Arterial supply :
Abdominal aorta Splenic arteryTrabecular artery Central arteries
Penicilliar arteriole Capillaries and sheetedarterioles sinuses of
red pulp
b. Open and closed theories of splenic circulation
c. Venous drainage
Sinusoid red pulp veins Trabecular vein
Splenic vein inferior mesenteric vein
Hepatic portal vein liver
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Structure of the red pulp of the
spleen
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Functions :
1. Production of blood cells
2. Destruction of erythrocytes
3. Defense of the organism : filter the blood
4. Storage of blood
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This incomplete encapsulated lymphatic
aggregates contain many lymphatic
nodules. They underlie the mucous
membranes (epithelial lining) of
oropharynx.
TONSILS
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The palatine tonsil
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MALTs
(Mucosa-associated lymphatic
tissues)
Lymphatic nodules are scatterred throughoutthe lamina propria of mucous membrane
exp : Peyerspatches
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Now I know
Structure and functions of the primarylymphatic organs and tissues
Structure and functions of the secondarylymphatic organs and tissues
Thank you
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