1st Lecture on Lymphoid Histology by Dr. Roomi

8/2/2019 1st Lecture on Lymphoid Histology by Dr. Roomi

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Click to edit Master subtitle styleHISTOLOGY OF LYMPHOID

SYSTEMBY

DR. MUDASSAR ALI ROOMI (MBBS,M. PHIL)


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Components of lymphatictissue

lymphatic tissue consists of two maincomponents:

1. Reticular tissue (reticular cells andreticular fibers)

2. Free or motile cells (lymphocytes,

macrophages and plasma cells)

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LYMPHOID SYSTEM

Synonym: Alsocalled as immune

systemDefinition:

Consists of cells ,

tissues andorgans designedto protect thebody from

invasion and 4/23/12 4


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Types of immunity

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distribution of lymphatictissue

Diffuse lymphatic tissue

Nodular lymphatic tissue

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Diffuse lymphatic tissue

Does not exhibitany special

organizationLocation: occurs

chiefly as aninfiltration of thelamina propria ofmucusmembranes,

particularly those 4/23/12 7


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Nodular lymphatic tissue

The cells are densely aggregated toform spherical structures calledlymphatic nodules (lymphoidfollicles).

Examples of lymphoid organs are:lymph nodes, spleen, tonsils, and

thymus.

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Structure of lymphaticnoduleDiameter: 200

um- 1mm.

TWO ZONES:

PERIPHERALZONE: stainsdarkly and

contains closelypacked smalllymphocytes.

GERMINAL 4/23/12 9


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LYMPH NODE

Oval or beanshaped bodiesfound along thecourse oflymphatic vessels

Usually occur ingroups.

Diameter: 1-25

mm 4/23/12 10


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Stroma (supporting framework) ofthe lymph node

Capsule: covers the whole lymphnode and is mainly composed of typeI collagen.

Trabeculae (septa): arise fromcapsule and extend into the interiorof the node.

Network of reticular fibers andcells: extend throughout thesubstance of the lymph node and

entraps the lymphocytes. 4/23/12 11


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Zones or regions of lymphnode

Cortex: outer zone, situated beneaththe capsule.

Medulla: inner zone, occupies centreof the L. node and its hilum.

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Cortex of the lymph node

It has incomplete compartments.

Lymphatic nodules (closely packed

lymphocytes) are present here.**B-lymphocytes are present here.***

Lymphatic nodules often contain

germinal centres (secondarynodules).*****

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Paracortex of lymph nodes

Inner to the maincortex

Devoid of lymphnodules

Composed ofsmalllymphocytes

T- Lymphocytesare present

here**** 4/23/12 14


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MEDULLA OF LYPM NODE

Medullary cords: composed oflymphocytes and

plasma cells.

No lymphaticnodules

Medullarysinusoids also arealso present here.

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IDENTIFICATION POINTS OFLYMPH NODE

Connective tissue capsule is present

Cortex and medulla is present

Lymph nodules are only situated inthe cortex and have no central

arterioles medulla contains Med. cords and

Med. sinuses

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FUNCTIONS OF LYMPHNODES

Filter lymph

Maintain and produce lymphocytes

Produce antibodies

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CLINICAL NOTE

Lymphadenitis: inflammation of thelymph nodes.

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CLINICAL NOTE

Lymphangitis:Inflammation oflymph vessels.

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CLINICAL NOTE

Metastasis to lymph nodes:spread of cancer from primary site tolymph nodes.

e.g. spread of breast cancer toaxillary lymph nodes

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1st Lecture on Lymphoid Histology by Dr. Roomi

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