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Lymphoid Functional Anatomy. The role of secondary lymphoid organs in trapping antigens For Tuesday Week 6 Practical Workshop, Dunnbook Chapter 10 Comments and Feedback please to the Author, Start/help. Left-click anywhere to continue.

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lymphoid functional anatomy

Lymphoid Functional Anatomy

The role of secondary lymphoid organs in trapping antigens

For Tuesday Week 6 Practical Workshop, Dunnbook Chapter 10

Comments and Feedback please to the Author,


using this presentation help

Left-click anywhere to continue

Left-click anywhere to continue

Left-click anywhere to continue

Using This Presentation – Help!
  • Navigate by clicking the Left mouse button
    • Some items within a page continue automatically to the next item, with never longer than a 3-second delay. Others need a manual mouse-click, including when the page ends to go to the next page. Hence you control the rate of presentation.
    • Don’t use the PageUp or PageDown keyboard buttons unless you want to skip through pages – you may miss things.
  • The Right mouse button provides a menu to allow you to skip and shortcut and repeat pages
  • Use this presentation in association with your Dunnbook
    • Comments in yellow boxes in this presentation have equivalent spaces on paper for you to complete, flagged by a
  • Here’s a good online medical dictionary if you need one…
  • …and some aids to find research papers and reviews..….

Help for this presentation

purposes of this presentation
Purposes of this presentation
  • To show how the siting of lymph nodes in the body, interconnected by lymphatic vessels, serves to trap pathogens at the local draining nodes
  • Examples are of material
    • inoculated through the skin: plague
    • injected to a muscle: an antigenic adjuvant
    • inhaled to the lungs: anthrax
  • To encourage you to explore areas you find interesting by following hyperlinks
  • To encourage you to keep your eyes open for features of interest and for the physical dimensions, especially of images

Presentation objectives

lymphatics and lymphoid organs overview
Lymphatics and Lymphoid organs, overview

From http://www.pedisurg.com4/ImagesPtEduc/lymph_nodes.gif

The lymphatics shown here are the superficial ones draining the skin. If all the lymphatics that drain organs were also shown, she would be green all over. Check that you know the difference between “lymphatic” and “lymphoid”.  Why is it important to know the routes of lymphatics in cancer patients?


Here is a more detailed view in a child. Note the chains of nodes

Lymphatics and Lymphoid organs, overview

lymph node chains in three body regions

Head & neck



Lymph Node Chains in Three Body Regions

Try palpating an accessible node: see ) especially if you or your practical partner has an infection which has caused one to swell


Lymphnode chains in three regions

surface locations of lymph node chains in head and neck


1 mm

Compare scale with next slide

Here’s a chance to revise your knowledge of:  Anterior, Posterior, Pre-, Supra-, Sub-….

Surface Locations of Lymph Node Chainsin Head and Neck

A typical active lymph node, e.g. in an infection

 Write a description of the immediate surroundings of the lymph node. The material in which it is embedded here is very typical.

Surface Locations of Lymph Node Chains

cancer enlarged lymph node with lymphoma

It’s pretty important for clinicians to get it right between lymph node enlargement due to an immune response, and to a tumour. That’s part of clinical training, but you could start thinking now how a scientific approach could assist in making the distinction

Cancer: enlarged Lymph Node with lymphoma

Pathologists are fond of food metaphors for the very inedible specimens they study. Can you think of other examples?

Compare scale with previous slide

Cut sections of this enlarged lymph node involved with high-grade non-Hodgkin's lymphoma in AIDS reveal a "strawberry sundae" appearance with swirls and globs of red in white.


An enlarged lymphomatous lymph node

abdominal lymphangiogram

 Sketch a stick-man schematic to make it clear from which view this X-ray was taken

  • Common Iliac Lymph Nodes
Abdominal lymphangiogram

This illustrates the connections between chains of lymph nodes by lymphatics


 What might be the likely biological purpose of arranging lymph nodes in a series of chains like this?

 Anything odd in this image?



The Black DeathNecrosis (gangrene) of the tissue caused by plaguefrom


If the history and current status of plague epidemiology interest you, see the recent WHO report

Fleas transfer the bacterial infection (Yersinia Pestis) from rodents by subcutaneous inoculation to various animals and topeople. Initial signs and symptoms may be nonspecific with fever, chills,malaise, myalgia (muscular pain or tenderness), nausea, prostration, sore throat and headache. Commonly a lymphadenitis (inflammation of the nodes) develops in those lymph nodes that drain the site ofthe flea bite, where there may be an initial lesion. This is bubonic plague,and it occurs more often in lymph nodes in the inguinal area and less commonly in the axillary and cervical areas. The involved nodes (“buboes”) become swollen, inflamed and tender and may suppurate (i.e. form or discharge pus). Once it has spilled into the bloodstream, the infection is systemic.



antigen transport by dendritic cells following intramuscular inoculation

The cells that have taken up the antigen are dendritic cells, shown in green in this higher-power view

Within the inguinal (draining) node the antigen is quite deep below the surface – the arrows mark the border. More on this next class

------------ in leg muscle at injection site ----------

in draining LN

100 mm

100 mm

10 mm

200 mm

3 hrs

48 hrs

48 hrs

48 hrs

Antigen (adjuvant) – red/orange

Dendritic cell marker (DEC205)- green

In the first couple of hours the antigen is not yet cell associated, but after two days most of it is internalised

Antigen transport by dendritic cells following intramuscular inoculation

Note the scale bar!

 What is an “adjuvant”?

Data from Dupuis et al, “Dendritic Cells Internalize Vaccine Adjuvant

after Intramuscular Injection“ Cellular Immunology 186: 18 (1998)

Antigen fate after i.m. injection

inhaled antigens the lung

Knowledge of functional lung anatomy is essential for clinicians to deal with infections that overwhelm the normal non-specifc immune defences which keep the alveoli normally sterile. Write a checklist of these defences.

Abstract schematic

Actual radiograph


Inhaled Antigens: the Lung

Pulmonary Lymphoid System comprises

  • Lymphatics- Originate in the pleura- Have valves- Drain towards hilum- Follow interlobular septa- Accompany blood vessels
  • Draining lymph nodes (shown yellow)
    • intrapulmonary
    • mediastinal

The bacterial disease anthrax is in the news as an inhaled pathogen. It is a toxigenic bacillus whose details you are not required to know. However, the next two pages make the point that the radiology of the lymph nodes can often give the quickest diagnosis, and reveal the role of the lymphoid organs when non-specific defences have been breached

Pulmonary lymphoid system 1

anthrax in a postal worker usa 2001

The infection begins with the inhalation of the anthrax spore. The ability to reach the pulmonary alveolus requires a spore size of less than 5 microns. The spore is engulfed by alveolar macrophages, and is transported through the pulmonary lymphatics to hilar and mediastinal lymph nodes.

Spiral CT through chest. Shows enlarged blood-filled lymph nodes (blue arrows) and fluid surrounding both lungs (red arrows). From

Anthrax bacilli after the spores have germinated, completely filling a pulmonary lymphatic (arrow)

Anthrax in a postal worker, USA 2001

With a lymphatic vessel filled like that, it isn’t surprising the outcome sadly was fatal


pulmonary lymphoid system in anthrax



Pulmonary lymphoid system in anthrax

CT imaging demonstrates bulky high-attenuation hilar and mediastinal lymphadenopathy which may produce bronchial and vascular narrowing. Large rapidly-progressive pleural effusions are characteristic. The portal of entry is the airway and the organisms are rapidly transmitted via the lymphatics to the intrathoracic lymph nodes and ultimately to the blood stream. Despite the inhalational acquisition of the disease, the lung parenchyma remains relatively uninvolved.From

Pulmonary lymphoid system 2

pathologies of lymph nodes
Pathologies of lymph nodes
  • If you have some time to spare you may like to visit which shows diseases involving lymph nodes of the head and neck, including:
    • Infectious Mononucleosis (“Glandular fever”)
    • Non-Hodgkin's Lymphoma
    • Persistent Generalized Lymphadenopathy
    • Cat Scratch Disease
    • Metastatic Carcinoma

You have probably by now mastered the meaning of “lymphadenopathy” since that has appeared a number of times, but  what about “lymphadenectomy”?

Pathologies of lymph noders

  • Pathogens at first encounter innate immune defences, e.g.
    • Skin epithelial barriers
    • Airway filtration and epithelial secretions
    • Phagocytosis, perhaps aided by opsonisation by Complement
  • If the defences are overwhelmed or bypassed, the pathogens travel via afferent lymph
    • in fluid phase or cell-associated
    • to draining lymph nodes
    • usually a chain of nodes are arranged in series
  • The adaptive immune response starts in the draining node