Lymphatic System
• Consists of:
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Lymph
Lymphatic vessels
Lymphatic tissue
Lymphatic nodules
Lymph nodes
Tonsils
Spleen
thymus
Lymphatic System
• Lymphatic Vessels– Functioning in returning interstitial fluid to the
vascular system.
• Lymphoid Organs and Tissues– House phagocytes and lymphocytes
– Activate the immune response
Lymphatic Vessels
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Return ISF to the bloodstream
Return leaked plasma proteins to the blood
Fluid within them is called lymph
1-way system flowing toward the heart
1 way systemback towardsthe heart
Blood Lymphaticvessel
PLASMA
vessel
LYMPH
INTERSTITIAL FLUID
or
TISSUE FLUID
Extracellularspace
How does lymph differ from plasma?
Lymphatic Vessels
• 4 types:–
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Lymphatic capillaries
Lymphatic collecting vessels
Lymphatic trunks
Lymphatic ducts
Lymphatic Capillaries
• What do they do?
Lymphatic Capillaries
• Blind
• Lined byendothelium– Loose
– Overlapping
• Permeability
• Flow
Lymphatic Capillaries
• Found just abouteverywhere that bloodcapillaries are found.– Exceptions
Lymphatic Capillaries
• Lacteals
– Specialized lymphaticcapillaries found in thevilli of the small intestine.
– Absorb fats from thedigestive tract.
Lymphatic Capillaries
Lymphatic
Collecting Vessels
-Similar to veins (in terms of the 3 tunics)
-Lots of valves
-Both superficial and deep
-Pass thru lymph nodes
* What happens to the lymph there?
What feature of lymphatic vessels is visible here? What do theyprevent? Why are they necessary?
Lymphatic Trunks
• Receive lymph from lymphatic collectingvessels.
• Types:–––––
JugularSubclavianBronchomediastinalIntestinalLumbar
Lymphatic Ducts
• Receive lymph from lymphatic trunks.
• Right lymphatic duct– Receives lymph from the right jugular, right subclavian,
and right bronchomediastinal trunks
– Empties into the right internal jugular vein
• Thoracic duct– Receives lymph from the left jugular, left subclavian,
left bronchomediastinal, intestinal, and lumbar trunks
– Empties into the left internal jugular vein
Lymphatic Vessels
Lymphatic Trunks
Lymphatic Ducts
Bloodstream
Where’s pressure high andwhere’s pressure low?
What makes lymph flow?
Lymph Flow
• Lymph flow will be similar to…
• 3 main factors promote lymph flow:– Skeletal muscle pump
– Respiratory pump
– Lymphatic smooth muscle
1. How does elevating an injured limb affectlymph flow?
2. How would exercise affect lymph flow?
3. How could massage affect lymph flow?
4. In some surgeries for breast cancer, thelymph nodes along thearm are removed inorder to assess the spread of the disease.What would be a result of this?
What happens when lymph cannot flow?
What could prevent lymph from flowing?
Filaria
• Lymphocytes– T lymphocytes
• Kill virus-infected and cancerous cells• Coordinate/control immune response
– B lymphocytes• Become plasma cells which secrete antibodies
• Phagocytes– Eat and kill and activate the rest of the immune system
• Dendritic cells– Activate the immune system
• Reticular cells– Make reticular fibers that support lymphatic tissues and
organs
Lymphoid Cells
Reticularconnectivetissue forms theframework ofmost lymphoidtissues andorgans.
Lymphoid Tissue
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Aggregations of lymphoid cells
Storage/proliferation site for lymphoid cells
Surveillance site
2 main types– Diffuse lymphatic tissue
– Lymphoid follicles
Diffuse Lymphatic Tissue
• What does “diffuse” mean?
• Found in lymph nodes and spleen.
• Especially prominent in the mucousmembranes lining the digestive, respiratory,urinary, and reproductive tracts.– Hence the term MALT.
Mucosa Associated Lymphatic Tissue
• Where are themucosae?
• Why is lymphoidtissue needed there?
• 2 main types:– GALT
– BALT
Lymphoid Follicles
• A.k.a. lymphoid nodules• Solid, packed spherical clusters of lymphoid
cells and reticular tissues• Often found as parts of larger lymphoid
organs (e.g., lymph nodes)• Found in the mucosae• Large number in the distal ileum and
appendix
Lymphoid follicle in thestomach
• Peyer’s Patches– Aggregates of lymphoid
follicles found in thedistal small intestine.
• Why there?
• Appendix– Blind outpocketing of the cecum.
– Contains aggregates of follicles.
Lymphoid Organs
• Surrounded by a capsule of denseconnective tissue.
• Lymph nodes
• Tonsils, thymus, spleen
Lymph Nodes
• Filter lymph
• Clustered alonglymphatic vessels
• Large superficial clustersin inguinal, axillary, andcervical regions.
Lymph Nodes
• Receive lymph from an afferent lymphatic vessel
• Drain lymph into an efferent lymphatic vessel
• Surrounded by dense CT capsule– Inward extensions (trabeculae) divide it into
compartments
• Reticular fibers support the resident macrophagesand lymphocytes
• Divided into a cortex and a medulla
Lymph Nodes
• Cortex contains:
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Subcapsular sinus
Cortical sinuses
Trabeculae
Diffuse lymphatic tissue
Lymphatic follicles
Lymph Nodes
• Medulla contains:– Medullary cords (diffuse lymphatic tissue)
– Medullary sinus
Flow Through the Node
Afferent lymphatic vessel
Subcapsular sinus
Cortical sinus
Medullary sinus
Efferent lymphatic vessel
What happens to the lymphduring this journey?
What does the lymph flowpast?
Spleen
• Largest lymphoid organ
• Sits just below the diaphragm,kind of behind the stomach andabove the kidney and colon.
• What protects it?
Spleen
• Major function is blood cleansing
– Removal of aged, broken, or malformed RBCs.• Who does this?
– Removal and destruction of pathogens and foreignmatter.
• Who does this?
Spleen
• Surrounded by a CT capsule w/ inward extendingtrabeculae
• Internal framework is provide by reticular fibers.
Spleen
• Splenic arterioles are surrounded by sheathesof lymphocytes.– This is known as the white pulp of the spleen.– What will happen here?
• The arterioles terminate in splenic capillaries –which are twisty, sinusoidal, and incomplete.– The capillaries and the surrounding splenic tissue
is referred to as the red pulp of the spleen.– Macrophages line the capillary surface.– Why?
Other Spleen Functions
• Storage of RBC breakdown products
• Platelet storage
• Fetal RBC production
Which wouldcontain moredamaged RBCsand morepathogens – thesplenic artery orthe splenic vein?
Thymus
• Largest and most activein fetus and infancy
• Involved in Tlymphocyte maturationand selection– Also, the removal of
those T cells that attackself tissue
• Growth ceases duringadolescence
• No direct fighting.
Tonsils
• Form a ring of lymphatic tissue at theentrance to the pharynx.
• 3 main types:– Palatine
– Pharyngeal
– Lingual
Palatine – located laterally in the posterior oral cavity.Largest and most often infected.
Pharyngeal – located in theposterior nasopharynx.A.k.a adenoids.
Lingual – located at thebase of the tongue.
Not fully encapsulated. Why not?
Contain crypts. What’s their advantage? What’stheir disadvantage?
Palatine Tonsil