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Anatomy of the lymphaticsystemThe immune system consists of a series oforgans and the vessels that connect them

Organs of the immune system have beencategorised into primary and secondarylymphoid tissue

The vessels that connect the organs are thelymphatic vessels (similar to blood vessels)

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5/1/12PRIMARY

Bone marrow

Thymus

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5/1/12SECONDARY

Site of antigen recognition and activation of the immuneresponse

Thus; Antigen dependent

Consists of;

1. Lymph nodes

2. Spleen

3. MALT

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Adaptive Immunity

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5/1/12The Lymphatic system

Lymphatic vessels (LV) found in mosttissues and organs

Similar to blood vessels, but the content

of fluid and cells differLymph derived from extracellular fluid

surrounding cells in any tissue or organ

Lower in protein content and blood

plasmaContains only lymphocytes and tissue

dendritic cells

Lymphatic vessels join the blood streamvia the largest lymphatic vessel, the

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5/1/12The Lymphatic System

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5/1/12Lymph Nodes

At regular intervals the lymphatic systemand a number of lymphatic vessels join atlymph nodes (LN)

LN are encased in a capsule consisting ofconnective tissue.

Afferent LV bring lymph fluid (containinglymphocytes and antigen) to the LN

Efferent LV carry the lymph fluid from theLN and eventually into the blood stream(via thoracic duct)

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Lymph Nodes

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Lymph Nodes

Medulla - containsplasma secretingcells

Cortex - primarily aB-cell areacontaining primaryfollicles and

secondary follicleswith GCs

Paracortex contains Tcells

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5/1/12Overview of lymphatic system

http://www.youtube.com/watch?v=qTXTDqvPnRk&feature=PlayList&p=E50AB139E755468E&index=42&playnext=2&playnext_from=PL

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5/1/12The Spleen

Located LHS abdomen ~12cmx5cm

Examination of spleen under the nakedeye reveals red surface with greyish

white specks.Known as red pulp and white pulp,

respectively

Spleen is surrounded by a collagenouscapsule and bundles of fibres calledtrabeculae

Trabeculae extend from the capsule into

the internal part of spleen, partially

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5/1/12Cross section of spleen

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5/1/12Functions of Spleen

Blood formation

All blood cells in fetus

Only lymphocytes, monocytes and dendritic

cells after birth

Blood filtration

Removes bacteria, particles (white pulp), wornout RBCs and platelets (red pulp), recycles iron

Primary follicles and secondary folliclescontaining GCs are found throughout spleen

Blood storage

Can contain over one pint of blood

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5/1/12Spleen

http://www.youtube.com/watch?v=DQDUlq2xILY

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5/1/12Mucosal Associated Lymphoid Tissue

Mucosal associated lymphoid tissue = MALT

Gut associated lymphoid tissue = GALT

Bronchial associated lymphoid tissue =BALT

Dual Functions: defence against pathogensand prevention of response to commensalflora, food antigens or inhaled antigens

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5/1/12Remember:

Skin is impenetrable.

Consequently mucosal surfaces are the majorroute of entry of pathogens into the body

N.B. Much larger lymphoid cell content thanthe classical lymphoid system

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5/1/12Tonsils and adenoids

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Tonsils lymphoid tissue under themucous membranes of the throat

palatine tonsils

pharyngeal tonsil adenoid

lingual tonsils

First line of defense

Tonsillectomy

Tonsils and Adenoids

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5/1/12ReCap

What are the two primary lymphoid organs?

What are the secondary lymphoid tissues?

What is contained within follicles of the lymph

nodes?What is contained within germinal centres of

lymph nodes?

What are the three functions of the spleen?

What are the dual functions of the MALT?