Chapter 22
Lymphatic System
&
Immunity
Lymphatic Functions
Fluid Balance – about 30L of fluid/day leaves capillaries
and enters tissues – only about 27L returns to capillaries
The extra fluids enters lymphatic system via the lymphatic capillaries
which merge to form larger vessels
Fat Absorption – Lacteals (special lymph vessels in the gut)
absorb fat and other substances from digestive system.
Chyle = Lymph + fat (has a milky appearance)
Defense – foreign substances & organisms filtered, recognized,
& attacked by lymphatic system
Lymph transport
of materials
Low in O2
Carries waste CO2
Carries metabolic waste products
Carries fat from digestive system
Major Components of
Lymphatic System
Lymphatic vessels (capillaries & veins)
Lymph nodules
Lymph nodes
Tonsils
Spleen
Thymus
Major Drainage Channels
Refer to material from Ch 21
Thoracic Duct drains lower limbs, abdomen, left thorax,
left arm – Ultimately drains into left subclavian vein
Cysterna Chyli – an expansion of the thoracic duct in
the upper abdomen – so named because it receives chyle
from the gut (chyle = fat laden lymph)
Right Lymphatic Duct – drains right arm, right side of head,
right thorax – empties into right subclavian vein.
#RLD is variable 1, 2 or 3 per person
Lymph Nodes – round/oval/bean shaped –scattered
throughout, these act as filters in the system
Lymphatic System Overview
Fig 21.28 p 672 (yes, prior chapter)
Fluid movement from
Circulatory into Lymphatic
Structure of Lymph Capillary
Lymph capillaries differ from blood capillaries because
they are blind-ended.
Fluid enters through pseudo-pores in capillaries
Pseudo-pores – overlapping (valve-like) endothelial cells
Internal valves also prevent backflow of lymph
Lymph flows because it is pushed from behind as more
fluid enters from the interstitial spaces
Lymph Nodes
Bean shaped, round or oval – these filters cluster in regions
like axilla, inguinal area, neck, gut
Function – constantly filter lymph as it flows through these
in-line filters
Lymph Node Structure
Externa capsule of connective tissue
Trabeculae – connective tissue fibers extending from
the outer capsule toward center
Lymph nodules – internal divisions of the lymph node
(like sections in an orange)
Germinal Center – region in nodules where new lymphocytes
are formed
Lymph veins entering & leaving node
Lymph Node
fig 22.4 p705
Tonsils
These are clusters of lymphatic nodules embedded in
connective tissue
Function – form a ‘defensive ring’ around the entrance
to the pharynx
Any microbes entering the body through the mouth or
nose are exposed to the immune system here
3 Types include:
Lingual – under tongue
Palatine – at sides of upper throat
Pharyngeal – between nasopharynx & oropharynx
Tonsils
fig 22.3 p 704
Spleen
Location – upper left quadrant of abdomen
Spleen is fibroelastic – it can expand/contract
Fibrous capsule with trabeculae extending inward (much
like a very large lymph node)
Contains lymphatic nodules (“white pulp”)
Contains venous sinuses (“red pulp”) which serve as a
storage area for red blood cells
Spleen Functions
Nodules in the “white pulp” region are part of the
Mononuclear Phagocytic System
Disease organisms & dead RBCs are destroyed by this system
“Red pulp” regions serve as a reservoir for RBCs
If you’ve ever felt the ‘left side abdominal cramp’ during
extended aerobic exercise (like running) you’ve felt the
spleen squeezing out extra RBCs
Spleen
(fig 22.5 p 707)
Gut Associated
Lymphatic Tissues
GALT – Gut Associated Lymphatic Tissue -- a diffuse
network of tissue occurring in the intestines.
GALT similar in structure/function to lymph nodules
Peyer’s Patches- lymph nodules found in the small intestine
and appendix
Lacteal ducts - lymph capillaries located in the gut wall,
absorb lymph from capillaries and fat from digestive system
(chyle = lymph + fat  milky appearance)
fig 24.11(p795)
Thymus
Triangular bi-lobed gland around the base of the heart
(remember cardiac anatomy here: the ‘base’ of the heart is at the top)
Surrounded by a connective tissue capsule with trabecular
fibers extending in to the interior dividing the gland into lobules
Each lobule has an outer cortex & inner medulla
Blood/Thymic barrier prevents substances in blood from
entering thymus
Thymic hormones produced here
Thymus is the site where T-lymphocytes mature
thymus
fig 22.6 p 708
The End.
22
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22
Lymph
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"Trust your hunches... Hunches are
usually based on facts filed away just
below the conscious level. Warning! Do
not confuse your hunches with wishful
thinking. This is the road to disaster."
-- Joyce Brothers,American psychologist and author
Chapter 22 continues…
The Lymphatic System
Immune Responses
Inflammatory Response
Inflammation – an acute localized response (reddening) of
the tissue to invading microbes. Symptoms include:
Swelling – as fluids move into tissues, area swells
Redness – blood vessels dilate & more blood flows to area
Pain – prostaglandins (produced by mast cells) stimulate
pain receptors
Abscess – includes dead neutrophils, dead microorganisms, as
well as pyrogens (fever promoters)
Heat – raises temperature above what bacteria can
tolerate – Fever is USEFUL!
Events of Inflammation
Blood flows to area  (histamine, kinins, complemenent,
& prostoglandins)
permeability of blood vessels   (as above)
Blood viscosity  … flows more slowly
Slowing of blood allows clotting mechanisms to begin
area walled off by fibrin clot preventing spread of invader
Events of Inflammation…
With  viscosity WBCs begin to marginating (lining up
along periphery like paving stones)
Diapedesis – after margination, WBCs begin amoeboid-like
movement out of vessels & into tissue
WBCs marginating also release chemicals to attract other
WBCs via chemotaxis
Opsonins (more on this soon) mark foreign cells for destruction
Inflammatory Response
Chemical Mediators of Inflammation
more… see Table 22.1 p 709
Histamine – a vasodilator released from Mast Cells
also increases blood vessel permeability
Mast Cells activated when antigen (foreign substance) is located
by an antibody and the antibody is then attaches to antigen &
to the mast cell. This event triggers release of histamine.
Kinins – plasma polypeptides vasodilator,  vessel permeability,
stimulate pain receptors, chemotaxis of neutrophils
Interferons – proteins that protect against viral infections &
some forms of cancer - don’t protect cell, don’t destroy virus
– bind to neighbors, stimulate production of anti-viral proteins
which inhibit viral replication (generic protection one stops many)
Complement Cascade
(another chemical mediator)
Approx 20 proteins – circulating in plasma in inactive form.
C1-C9, Factors B,D & P (properdin)
Cascade – each activates the protein next in sequence…
much like falling dominos
C3 can be activated at least two different ways (see fig.)
promote phagocytosis – chemotaxic to several cell types
Lyse invading cells – (C5-C9 form a pore)
Activation
Complement Cascade fig22.7
C3-7 promote
phagocytosis
C5-C9 form
pores (holes) in the
plasma membrane
of invaders (shotgun defense)
Innate Immunity
See table 22.2 for details
Immune response that is similar for each exposure – no
‘remembered response’
Neutrophils, Monocytes, Macrophages, Basophils
Mast Cells, Eosinophils, Natural Killer Cells
Innate Cellular Immunity
see fig 22.2 – nice summary
LEUKOCYTES – White Blood Cells (several types)
Neutrophils – small phagocytic cells, quick response, short life.
Can leave blood stream and enter tissues. Often first on scene,
Pus is dead neutrophils, microorganisms & tissue residue
Release lysosomes - kill microorganisms, damage tissue & inflammation
Macrophages – Monocytes which leave the bloodstream
large phagocytic cells, leave blood & enter
tissues, usually on scene after neutrophils & do late stage
clean up. Produce: interferons, prostoglandins, complement
Basophils – leave blood, enter tissue, produce chemicals
to promote inflammation
More Innate Cellular
Mast Cells – non-moving. Stay in connective tissue near
potential entry points of the body – skin, lungs, GI tract etc.
Release chemical defenses – which bring on inflammation
Eosinophils – leave blood to enter tissues. Produce enzymes
to break down chemicals from Mast cells & basophils. Kill
some parasites. High numbers when inflammation occurs.
Natural Killer (NK) Cells – Recognize cell types (tumor or
virus infected cells) and destroy those cells, damage cell
membranes. No ‘memory’ so grouped with Innate Immunity.
Adaptive Immunity
Ability to recognize, remember and respond to foreign antigens
Antigen – a substance that is recognized by antibodies
Antigens can be:
Self – produced by the body (tumor fighter or autoimmune)
Non-Self – foreign e.g. bacteria, viruses, transplant tissues
Antigens
Adaptive Immunity
T and B lymphocytes – origins in red bone marrow
T-Cells: Cell-Mediated immunity – cells themselves attack
invaders
T-Cells mature in thymus
B-Cells: Antibody-Mediated immunity – cells produce
antibodies which attack invaders
B-cells mature in red bone marrow
B/T Cell Origins
Two basic types of immunity
Natural – immunity we are born with
Acquired – immunity due to an outside source
a. Passive – taking on a large dose of antibodies
made somewhere else (e.g. - gamma globulin shot)
b. Active –your system stimulated to produces an
immune response. Disease organism, vaccination
Vaccination
Vaccination works by presenting the antigen to the
immune system.
Killed but recognizable
Live/disabled
Antigenic fragment – not the whole organism, just the
‘recognizable bit’
Chapter 22… day 3
Today we deal with
Adaptive Immunity…
The ability to recognize, respond to and remember
particular antigenic substances
Cell Markers
Major Histocompatibility Complex Proteins – recognizes self
MHC-I & MHC-II (matched in tissue transplants)
Minor Histocompatibility Complex Proteins – MHC-II
minor determiners of self
Macrophages rub against cells, IF they find MHC-I or
MHC-II they leave the cell alone. IF NOT or if they find a
recognized antigen they do something else.
No MHC – invader is attacked!
Lymphocytes
B-Cells provide humoral immunity (antibodies)
activated in bone marrow
T-Cells provide cellular immunity
activated in thymus
Cells sometimes also labeled
• Helper-T = CD4 (or T4)
“CD” for cluster of differentiation
• Cytotoxic-T= CD8 (or T8) (system for naming cell surface
markers)
• Inducer-T
• Suppressor-T
• Memory-T
Antigen processing
Foreign antigens are taken in by antigen processing
macrophages these are fitted onto MHC-I or MHC-II
molecules
This MHC/antigen complex is reinserted into the cell surface
membrane
Costimulation
The pairing of MHC-II and an antigen with an antigen
receptor serves as a signal to activate a Helper-T cell
Is this guy
causing
trouble?
Yep!
Ok, I’ll take care of
him and all of his
buddies`
Helper Cells (CD4s)
Secrete cytokinins (cell chemicals) which:
Stimulate T cell division to produce Memory Ts
Aid maturation of Killer-T cells
Attract macrophages & Natural Killer(NK) cells
(nonspecific immunity encouraged)
Promote B cell and antibody production
Helper T proliferation
Cytotoxic & Memory Ts
Cytotoxic-T (“killer-T”) cells activated by exposure to
antigens bound to MHC-I. … then divide to produce
more Cytotoxic T (Tc) cells and Memory-T cells
The Tc cells roam injured tissue destroying anything
with the target antigen
Rupture membrane using perforin
secrete poison (lymphotoxin)
turn on self destruct signal in invader (apoptosis)
Memory T cells don’t respond. Instead, they wait. If another
occurrence of the same antigen is detected they immediately
begin differentiating into new Tc cells
Inducer & Suppressor-T
Induce or Depress responses of other T & B cells
Suppressor-Ts release ‘suppression factors’
following the initial immune response
B-Cells – Humoral Immunity
Antibody Producers
Triggered by
Helper-T Cells
Antibody Classes
Imunoglobins
IgG
IgM
IgA
IgE
IgD
Antibody Class Functions
IgG – activates complement, functions as an opsonin,
promotes phagocytosis, can cross placenta to provide
immunity to fetus and newborn – responsible for RH
reaction (hemolytic disease in newborn)
IgM – activates complement, acts as antigen binding receptor
on surface of B cells, responsible for Aglutination in ABO
blood transfusions occurs in pentamers (five together)
IgA – secreted in saliva, tears, mucous membranes, protectio
lymph
lymph
lymph
Antibody Class Functions…
IgA – secreted in saliva, tears, mucous membranes, protection
on body surfaces. Present in colostrum and milk to provide
temporary immunity to newborn.
Structure – dimer (two together
IgE – tends to produce parts of inflammatory and allergic
responses, binds to Mast Cells & Basophils
IgD – functions as an antigen binding receptor on B cells,
thus these are attached to surfaces of the B cells while
others are free floating
End of Chapter 22…
Be sure to look over lab materials
Good luck studying for the exam!