The Lymphatic System
February 2009
Functions



drains and filters protein containing
fluids from tissue which has escaped
from blood capillaries
transport fats from gastrointestinal tract
to the blood
defense – protect the body from foreign
cells, microbes, cancer cells
Lymph vessels
Major Structures of the Lymphatic
System




Fluid
lymph
Vessels
lymph nodes




Tonsils
Adenoids
Spleen
thymus
Lymph Organs
Structure Details


lymph – clear and colorless; composed
of water, lymphocytes, nutrients,
hormones, and salts; also known as
intercellular or interstitial fluid.
Originates in blood plasma
lymph vessels – carry fluid; more
permeable than blood capillaries
Lymph
Structure Details
lymph nodes – small round structures located
in lymph vessels; they are located in clusters in
the following areas: cervical (neck), axillary
(armpits), pectoral (chest), abdominal
(stomach), inguinal (groin area), popliteal
(back of leg, behind knees)


Function: they fight disease by producing
antibodies, removing bacteria or malignant cells,
and filtering foreign substances; contains large
amounts of lymphocytes and macrophages
Structure Details
tonsils & adenoids- lymph tissue located in
the upper portions of the nose and throat
spleen – largest lymphatic organ composed of
lymph tissue that is located in the left upper
quadrant of the abdomen



Function: production of B lymphocytes;
phagocytizes bacteria and worn out damaged RBC;
stores and releases blood in case of demand
Structure Details


thymus- lymph tissue; located on top of
heart, reaches maximum size in puberty
and decreases thereafter
Function: help produce T- cells
Cells of the lymphatic system



macrophages – large phagocytic cell (cells
eats bad stuff) (like pacman chew it up)
lymphocytes – originate in the bone marrow;
type of white blood cell that provides
immunity
Two types T- lymphocytes & B – lymphocytes
Macrophage
Lymphocytes



T lymphocytes – respond to foreign antigens
by attaching to the foreign object or cell
(interact directly with the cells – called cellmediated immunity);
attack cancer cells, but the problem arises when
the cancer cells divide faster than the T cells can
kill them.
4 types –




natural killer T cells
cytotoxic t cells – cause apoptosis or programmed cell
death
memory t cells – remember past antigens for quicker
response
Suppressor t cells – suppress immune system to prevent
over-reaction to known foreign antigens.
Lymphocytes Continued
B
lymphocytes – respond to foreign antigens by
producing antibodies that destroy the antigenbearing particles (don’t kill cells directly – called
antibody-mediated immunity)
 B lymphocytes “taste” foreign antigens, so that
they can then make appropriate matching
antibodies which can attack the foreign invaders.
 Antibodies (immunoglobulins) – destroy any cell
that bearing the matching antigen.
Cells of Lymphatic

If a microbe that can cause infection
gets past your body’s initial barriers
(mechanical barrier) First line of
defense (skin, mucus), T cells are the
army troops that do the fighting (B cells
are the armed guards that hold a
grudge).
Antigen vs Antibody



Antigen – proteins, polysaccharides, lipids
that are located on a cells surface that
elicit an immune response. Chemical
markers
Self antigens- proteins that the body cells
recognize as “self”
Non-self- proteins that the body does not
recognize
Continued…



Antibody – protein that B cells produce in
response to the presence of a non-self
antigen
When an antibody combines with an
antigen, it renders the antigen-bearing
cell/particle inactive and leads to the
destruction of the cell.
Causes agglutination or massing of cells
together so they can be destroyed by mig
Agglutination of anitgens with
matching antibodies
Nonspecific Defense



mechanical barrier: physical barrier between
the body and pathogen. Ex: skin, mucous
membranes, cilia, epiglottis. First line of
defense for the body
species resistance: a given organism develops
diseases that are unique to it. Examples are
mumps, gonorrhea and syphilis infect humans
but not other animals.
Disease may affect different animals differently
Nonspecific Defense




all except mechanical barrier are second line of
defense
chemical barrier: enzymes in body fluid that can
damage, kill or make the environment
uninhabitable for the pathogen. Ex. Gastric juice,
tears, salt in sweat
fever: endogenous pyrogen (protein) raises the
set point in the brain for body temperature. The
higher temperature reduces the levels of iron in
the blood that the pathogen needs to survive.
Also, phagocytic cells attack more vigorously
inflammation: redness, swelling, heat, and pain
due to a pathogen invasion, inhibits microbial
growth. Decreases blood flow through the area.
Specific Defense (Immunity)



Third line of defense
resistance to particular pathogens or to
their toxins
cell-mediated immunity – this is where
T-cells, B-cells, and macrophages are
activated.
Specific Defense (Immunity)


Antibody-mediated immunity
Immune responses


Primary immune response – B cells and T cells
are activated and fight the pathogen. Antibodies are produced (takes 5-10 days to reach
detectable levels)
Secondary immune response – Some of the B
cells activated by the primary response remain
dormant as memory cells; if the antigen is
encountered in the future, the memory B cells
immediately begin to produce the antibody
Active and Passive Immunity



Active immunity – results when a person
produces an immune response to an antigen
that is long-lasting
Occurs naturally when a person is exposed to
a pathogen and develops a disease; person
gains resistance by initiating a primary immune
response.
The primary immune response gives immunity
or a secondary immune response.
Active Immunity Continued


Occurs artificially when a person receives a
vaccine (bacteria or viruses that have been
killed or weakened so they can’t cause a
serious infection); but they still contain
antigens that stimulate an immune response;
doesn’t always last for life.
Still activates a secondary immune response
Passive Immunity



occurs when a person receives antibodies
produced by another individual; person does not
have an immune response, so immunity is shortterm
Occurs naturally when antibodies pass from
mother’s blood into fetal bloodstream, also thru
breastfeeding; fetus acquires immunity against
pathogens that mother has developed immunity
against; lasts 6 months to a year after birth
Occurs artificially when a person receives
antiserum (ready-made antibodies)
Types of Acquired Immunity
Type
Mechanism
Result
Naturally acquired active Exposure to pathogens
immunity
Symptoms of disease and
an immune response
Artificially acquired
active immunity
Vaccine
Stimulation of immune
response without
severe symptoms of
disease
Artificially acquired
passive immunity
Injections of antibodies
(antiserum)
Short term immunity
without an immune
response
Naturally acquired
passive immunity
Antibodies passed to
fetus
Short term immunity for
infant without
immune response
(lasts 6 mon to 1 yr)
Vaccines

mixtures of antigens (killed microbes,
those that are unable to cause infection,
or proteins not recognized as self)
Administered orally, nasally, inoculation not for life – usually repeated
Immune System Concerns

Three types of immune system disorders



Autoimmune Diseases
Allergies
Immunodeficiency's




autoimmune diseases –
a. your system attacks your own self cells
b. Occurs when bacteria/virus causes T cells to
attack body’s own macrophage. Eventually
killer T cells start to view other cells in the
body as foreign
c. Ex. Lupus, Rheumatoid arthritis, multiple
sclerosis



Allergies –
a. Allergens cause the system to have a
hypersensitivity reaction which causes an
excessive immune response. Severity can
change year to year and some start late in life
– genetics can predispose people to allergies
b. Delayed reaction allergy results from
repeated exposure to antigens
Allergies Continued


c. IgE antibodies cause the release of
histamine …. Initiating allergic reactions
which can damage the tissues in the body
d. dilation of blood vessels, increased
vascular permeabilty, swelling, contract of
bronchial and smooth muscles, increased
mucous production
Allergies Continued



e. the result is severe inflammation- hives, hay
fever, asthma, or gastric disturbances
f. some are seasonal and others are year round
(food)
g. A severe allergic reaction (sudden breathing
difficulty) is anaphylaxis can cause anaphylactic
shock which can lead to death – treatment is an
epinephrine injection or tracheotomy. Symptoms
of an anaphylactic shock: hives, vomiting,
diarrhea, face, tongue and larynx swell
Immunodeficiencies


(acquired immunodeficiency syndrome) is
caused by HIV (human immunodeficiency
virus. HIV targets helper T cells, which makes
a person infected unable to fight against this
virus.
Over time, the person is deficient in helper T
cells  immunodeficiency. It is acquired
(rather than induced) via lifestyle choices
(unprotected sex, intravenous drug use) or
events (blood transfusions)
Immunodeficiencies



initial symptoms- weakness, recurrent fever,
night sweats, swollen glands, weight loss
(similar symptoms of the flu)
latency period- 5-10 years person feels well,
immune system struggles with growing HIV
invading cells
AIDS (third stage)-opportunistic infection.
Those infected don’t die from AIDS, they die
due to the flu, pneumonia, etc because their
immune system is so weak, they can’t fight
anymore.