LYMPHATIC /DISEASE
RESISTANCE
Lecture Notes:
LYMPHATIC SYSTEM
I. Functions of lymphatic system
System is made up of drainage ducts, vessels and lymphatic tissue that is essentially
an organized collection of lymphocytes and macrophages (monocytes).
A) returns lymph (produced by excess extracellular fluid) to the venous system
B) provides sites to promote resistance to disease.
II. Lymphatic circulation
A. Lymphatic capillaries
1. Blind-end capillaries
(not flow through like blood capillaries) pick up excess extracellular
fluid (which becomes lymph fluid)
2. Filtration holes larger
than blood capillaries allow larger molecules to be absorbed (like dietary fats)
B. Lymphatic vessels
1. Similar to veins (walls
thinner with valves)
2. Pass through lymph nodes
on way
3. Movement of lymph via
skeletal muscular pumping just like movement of blood through veins
C. Lymphatic routes--lymph
passes through nodes and eventually passes into two main ducts 1.
Right lymphatic DUCT empties into R subclavian V- drains upper right extremity,
right head & neck & right thorax & organs
2. Left lymphatic DUCT
(=thoracic) empties into L subclavian V-drains lower extremities, upper left
extremity, head, neck & thorax. Also intestinal area via lacteals (lymphatic
capillaries in intestines that absorb fats from food) that drain into cisternae
chyli
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III.
Lymphatic organsA.
Lymphatic nodule 1.
Basis for most lymphatic organs
Contains lymphocytes and macrophages which provide the functions.
2. Functions
a.
lymphocytes, mostly B cells, produce antibodies (which agglutinate, neurtralize
or immobolize acellular/cellular antigens)
b. Macrophages phagocytize
microbes
B. Aggregates of nodules
Tonsils and adenoids in mouth, Peyer's Patches in intestines Functions
same as nodules but on saliva or food
***Most of lymphatic
tissue in body is diffuse and located along the digetive mucuosa (or gut) and
make up the mucosa (or gut) associated lymphatic tissue (MALT or GALT). So...tonsils,
adenoids, Peyer's patches are all part of that group and have similar functions
(see nodule) .
C. Lymph node 1.
Structure a. CT
capsule
b. Cortex (outer portions)
1) Lymph vessels into
node
2) Nodules with lymphocytes
c. Medulla 1)
Lymph vessels out
2) Macrophages reside here
2. Functions same
as nodules but on lymph fluid
D. Spleen
1. Structure a.
Similar but larger to lymph nodes
b. Blood vessels-not lymph
2. Functions same as
nodules but on blood
E. Thymus
gland (between sternum & lungs)
largest & most important in infants--small but functional in adult
1. Structure--CT fibers
packed with lymphocytes in lobes
2. Function
a.
Produce thymosin which promotes development of T lymphocytes making them immunocompetent
(maturation)
F. Red
Bone Marrow- Original site of lymphocyte production before migration. B-cells
become immunocompetent before moving to lymphatic organs. T cells have to pass
through Thymus and be affected by Thymosin before they become mature
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List
the lymphatic organs, describe their structure. Describe the function of lymphocytes
and macrophages.
DISEASE RESISTANCE
Grouping of physical, chemical and cellular mechanisms to prevent and resist
infection and disease. All of the mechanisms are interconnected and act at same
time. Non-specific disease resistance mechanisms act first but are relatively
inefficient. Specific disease resistance (immunity) takes a week or so to respond
but acts effectively.
I . Non-specific resistance mechanisms (Innate immunity)
A. Skin & mucous
membranes barrier 1.
Mechanical a.
keratinized eipdermis provide physical barrier to prevent infection, constant
replacement by mitosis allows adhering pathogens to be removed
b. Mucous flow in respiratory
and digestive systems removes pathogens, urine flow in urinary system removes
pathogens, sweat washes pathogens off surface.
2.
Chemical a. Exocrine
secretions inhibit bacterial growth (oil and sweat) or destroy microbe membranes
(lysozymes in sweat)
b. Low pH (very acid) of
stomach and vagina denatuer proteins of microbes
3)Cellular
macrophages (phagocytic cells) are resident in skin
mast cells (histiocytes) secrete histamines and leukotrienes to increase inflammation.
B. Nonspecific cellular defenses
1. Phagocytosis
a) neutrophils and macrophages are attracted to chemicals (including complement
protein) produced during cell injury or infection.
b) pathogens adhere to phagocyte membrane (with help of complement protein)
c) phagocytes engulf foreign substances and digest with lysozymes (digestive enzymes)
d) pathogen generally broken up into molecules or particles and dies as result
of digestion
e) neutrophils also secrete peroxide to destroy remaining pathogen particles;
or
macrophages move pathogen molecules (antigens) to membrane and present antigen
to lymphocytes (which stimulates immunity)
2. Natural killer (lymphocyte)
cells secrete perforin to lyse cell membranes, and lymphotoxin to poisoninvading
cells.
C. Inflammatory
response
1. Inflammation
Certain cells (basophils and mast cells, for instance) secrete inflammatory chemicals
(histamine) to increase blood flow via increased vasodilation and capillary membrane
permeability
More fluid brings: more phagocytes: more RBC and oxygen: more glucose: more antibodies:
more clotting proteins: more antimicrobial substances; remove dead cells
2. Phagocyte migration
a. Injured cells also release
chemicals (complement proteins) which are attractive to phagocytes so they move
into area and through vessel walls
3. Repair
Increased fluid with increased materials sets stage for repair
D.
Antimicrobial substances (blood proteins) 1.
Defensins (amino acids) produced by neutrophils are effective against bacteria,
viruses, fungi (non-specific)
2. Interferons (proteins)
produced by virus-infected lymphocytes are effective in other cells attacked
by viruses by blocking viral RNA translation
3. Complement (proteins
in blood) system production activated by antigen/antibody complex .
causes
cytolysis
promote inflammation
promote phagocytosis
E. Fever
destroys bacteria by denaturing their proteins and increases effectiveness of
interferons.
Compare
and contrast the functions of the five categories of non-specific disease resistance
mechanisms. Describe how complement proteins act to connect or "complement"
specific and non-specific mechanisms.
II. Specific resistance
to disease (adaptive immunity)
A. General information
1. Immunity is result
of actions by lymphocytes
a) cellular (T lymphocytes)
b) humoral or antibody (B lymphocytes)
2. Millions of unique types of lymphocytes, each with a specific receptor for
one type of pathogen, bind to an antige to become activated..
3. Immune system is inherited
(i.e., potential for action is there but needs to be activated)
4. Immunity has memory
(residual cells from first infection results in faster action during second
invasion) but takes longer than non-specific mechanisms because it requires
production of many new lymphocytes.
B.
Antigen recognition 1.
Processed antigen (foreign) consumed by macrophage and presented to lymphocytes
2. Activation of lymphocytes
a. B-cells bind with
free antigens which cause clonal increase in number and type.
b. T-cells must check if
antigen is self (must be presented to antibodies with human leukocyte associated
(HLA) antigens from major histocompatible complex genes (MHC) before T-cells
can recognize).
need self/nonself complex to activate & cause clonal increase in number
and type
need costimulator (chemicals like leukotrines)
C.
Cell--mediated immunity (T-cells) 1.
T-cells activated and undergo proliferation.
2. T-cells diversify
a. Killer T-cells (cytotoxic)
T-cells move--out to viral infected cells and bind. Then they
a) produce perforin to break infected cell menbranes (cytolysis)
b) produce lymphotoxin to poison infected cell.
b. Helper T-cells
Once activated they secrete chemicals that promote T-cell & B-cell cell
proliferation
c. Memory T-cells remain
in blood and their greater numbers increase rate of response for second infection
D. Antibody--mediated
immunity (B-cells) 1.
B-cells activated and undergo proliferation.
2. B-cells diversify
a) plasma cells which
remain in lymphoid tissue (spleen) secrete antibodies.
b) Memory B-cells--remain
in blood and their greater numbers increase rate of response for second infection
3. Antibodies similar
to B cell receptors that bind with antigen
4. Antibodies form complexes
with antigens =antigen/antibody complexes that:
a) neutralize antigen
by covering (smotthering) microbe
b) agglutinate antigens
sticking them together
c) precipitate soluble antigens into a solid
d) immobolize swimming antigens
(all of these actions make antigen more available for phagocytosis)
d) activate complement proteins which:
lyse cells
promote inflammation
promote phagocytosis
An
interesting article on antibodies in breast milk
Describe
how T and B cells actually destroy pathogens. Include specific actions of perforin,
lymphotoxin, antibodies and complement proteins.
Professor
Thomas M. Lancraft
Human Anatomy and Physiology
Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
9/2008