Lymphatic System Lecture

8/6/2019 Lymphatic System Lecture

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16:10

1l’Univeristé d’Ottawa / University of Ottawa

The Anatomy and Histologyof the Spleen and Lymphatic

System

The Anatomy and HistologyThe Anatomy and Histologyof the Spleen and Lymphaticof the Spleen and Lymphatic

SystemSystem

Dr. Bruce BurnsDept of Pathology andLaboratory Medicine

Dr. Bruce BurnsDept of Pathology andLaboratory Medicine

Université d’Ottawa / University of Ottawa 16:102

Université d’Ottawa / University of Ottawa

Université d’Ottawa / University of OttawaUniversité d’Ottawa / University of Ottawa

Why do we have a lymphaticsystem?Why do we have a lymphaticWhy do we have a lymphaticsystem?system?q Acts as a “sponge” to resorb fluid

(lymph) from the interstitial space >prevents edema

q transports foreign substances toregional lymph nodes > immune response

q Acts as a “sponge” to resorb fluid(lymph) from the interstitial space >prevents edema

q transports foreign substances toregional lymph nodes > immune response



Features of the lymphatic capillaryFeatures of the lymphatic capillaryFeatures of the lymphatic capillary

q Porous “blind ended” channelspresent in the interstitium of mostorgans (not brain)

q often collapsed, very difficult to seeunless injected

q lined by endotheliumq larger lymphatics may have valves

and smooth muscle coats

q Porous “blind ended” channelspresent in the interstitium of mostorgans (not brain)

q often collapsed, very difficult to seeunless injected

q lined by endotheliumq larger lymphatics may have valves

and smooth muscle coats



Main thoracic/abdominallymphatic vesselsMain thoracic/abdominalMain thoracic/abdominallymphatic vesselslymphatic vessels

• Cysterna chyli in abdomen receiveslymph from intestinal lymphatics -important for fat absorption• Thoracic duct carries lymph from lowerlimbs and abdomen, emptying into venousblood system at junction of left jugular andsubclavian veins



Lymphatics of head, neck andaxillaLymphatics of head, neck andLymphatics of head, neck andaxillaaxilla

• Scalp drains to cervical nodes• Oral cavity/throat drains tocervical nodes• breast and arm drain toaxillary nodes





Leg Lymphatic DrainageLeg Lymphatic DrainageLeg Lymphatic Drainage

• Drain to superficial inguinal lymph

nodes• no other significant lymph nodes in legdistal to inguinals



Lung lymphaticsLung lymphaticsLung lymphatics

• Lymphatics follow

bronchovascularstructures drainingcentrally• surround alveoli• meshwork onpleural surface

Lymphaticsin yellow



What are the major lymphoidorgans ?What are the major lymphoidWhat are the major lymphoidorgans ?organs ?q lymph nodesq extranodal lymphoid tissue -

– tonsils – spleen – mucosal associated lymphoid tissue

(MALT)q thymus

q lymph nodesq extranodal lymphoid tissue -

– tonsils – spleen – mucosal associated lymphoid tissue

(MALT)q thymus



Basic Anatomy of a Lymph NodeBasic Anatomy of a Lymph NodeBasic Anatomy of a Lymph Node



Lymph Node Histology - low powerLymph Node Histology - low powerLymph Node Histology - low power

Benign (reactive)follicularhyperplasia oflymph node

1.8 cm



Sinus histiocytes

Mantle zone B-cells

Germinal Center





B and T cell distribution in lymph nodesB and T cell distribution in lymph nodesB and T cell distribution in lymph nodes

B cells infollicle

T cells inparacortex Université d’Ottawa / University of Ottawa 16:10

14Université d’Ottawa / University of Ottawa

Antigen Presenting cellsAntigen Presenting cellsAntigen Presenting cells

q B-cell zone (Germinal Center) – follicular dendritic cells

q T-cell zone (Paracortex) – interdigitating reticulum cells

q both present antigen in the contextof self-MHC molecules

q B-cell zone (Germinal Center) – follicular dendritic cells

q T-cell zone (Paracortex) – interdigitating reticulum cells

q both present antigen in the contextof self-MHC molecules



Clinical importance of lymphaticdrainage and lymph node locationsClinical importance of lymphaticClinical importance of lymphaticdrainage and lymph node locationsdrainage and lymph node locationsq If blocked lymphedema develops

– occurs after some surgery/radiation onlymph nodes

q anatomy of lymphatic drainage isconsistent, metastases from organsfollow typical pattern of spread

q inflamed (tender) nodes suggestinfection in area of drainage

q If blocked lymphedema develops – occurs after some surgery/radiation on

lymph nodesq anatomy of lymphatic drainage is

consistent, metastases from organsfollow typical pattern of spread

q inflamed (tender) nodes suggest

infection in area of drainageUniversité d’Ottawa / University of Ottawa 16:10

16Université d’Ottawa / University of Ottawa

Functions of the SpleenFunctions of the SpleenFunctions of the Spleenq “organ of mystery” in antiquityq Red Pulp- filtering function

– RBC’s “boot camp” - must shape up• lose nuclear remnants (Howell-Jolly

bodies) Pitting • able to deform through sinusoidal wall

and endothelium Culling – macrophages filter and destroy foreign

material in blood Macrophage activation

q “organ of mystery” in antiquityq Red Pulp - filtering function

– RBC’s “boot camp” - must shape up• lose nuclear remnants (Howell-Jolly

bodies) Pitting • able to deform through sinusoidal wall

and endothelium Culling – macrophages filter and destroy foreign

material in blood Macrophage activation



Functions of the Spleen - 2Functions of the Spleen - 2Functions of the Spleen - 2

q White pulp - immunologic functions – trapping and processing of antigens –

the major site of antibody synthesis – key role in removal of encapsulated

bacteria (Strep pneumo)

q White pulp - immunologic functions – trapping and processing of antigens –

the major site of antibody synthesis – key role in removal of encapsulated

bacteria (Strep pneumo)



Spleen - Gross AnatomySpleen - Gross AnatomySpleen - Gross Anatomy





Spleen - Gross featuresSpleen - Gross featuresSpleen - Gross features

• “normal” weight = 50-250 GMS• Splenic artery from celiac trunk,courses along length of pancreas• Splenic vein returns to IVC



Microanatomy of the SpleenMicroanatomy of the SpleenMicroanatomy of the Spleen



Splenic Red Pulp ArchitectureSplenic Red Pulp ArchitectureSplenic Red Pulp Architecture• Arterial blood emptiesinto splenic cords ofBillroth• blood cells must squeezethrough endothelial cellsto get back into sinuscirculation



Histolog ic features of the SpleenHistologic features of the SpleenHistologic features of the Spleen

Red Pulp

WhitePulp



Red Pulp HistologyRed Pulp HistologyRed Pulp Histology

CordsSinus



Splenic sinus basementmembrane - “ring fibers”Splenic sinus basementSplenic sinus basementmembrane - “ring f ibers”membrane - “ring fibers”

Sinus

Ringfibers





White Pulp HistologyWhite Pulp HistologyWhite Pulp Histology

Marginal zone

Germinalcenter

Mantle zone



Splenic OdditiesSplenic OdditiesSplenic Oddities

q Asplenia - congenital absence, oftenassociated with cardiac abnormalities

q Accessory spleens - small deposits of“normal” spleen in abdomen

q splenosis - post-traumatic seeding of“baby spleens” in the peritoneumfollowing splenic rupture

q Asplenia - congenital absence, oftenassociated with cardiac abnormalities

q Accessory spleens - small deposits of“normal” spleen in abdomen

q splenosis - post-traumatic seeding of“baby spleens” in the peritoneumfollowing splenic rupture

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Lymphatic System Lecture