Download Function of the Lymphatic System

The
Lymphatic
System
Function of the Lymphatic System
• #1: It returns excess
interstitial fluid to the
blood.
• Of the approx 90%
returned by osmosis to
the blood almost
immediately; the 10%
that does not return
becomes part of the
interstitial fluid which
surrounds cells in our
tissues.
Refer to page 323 of text for this picture showing
the relationship of the lymphatic system to the
cardiovascular system
• During filtration in the
capillaries a tissue
fluid from blood
plasma remains in the
interstitial spaces and
must be returned to
the blood via
lymphatic vessels.
• Without this return
blood volume and BP
would decrease.
Thoracic duct
Rt lymphathic
duct
Cisterna chyli
• Function #2 of the
lymphatic system is
the absorption of fats
and fat-soluble
vitamins from the
digestive system, and
transport them to
venous circulation.
• Duodenum mucosa
have fingerlike
projections called Villi;
• Here a specialized
lymph capillaries
called Lacteals that
absorb fats, and the
fat-soluble vitamins.
• Vitamin A, D, E, and
K.
• Function # 3 is to provide
the bodies defense
against invading
microorganisms and
disease processes.
• Here complex lymphatic
tissues (lymphocytes
within connective tissue,
that have been produced
from stem cells in the red
bone marrow, migrate to
lymph nodes and
nodules, lymph tissues, to
the spleen, and thymus.
Definitions to know:
• Lymph: a fluid similar to blood plasma and
derived from blood plasma that
accumulates as the blood passes through
capillary walls near the arterial end. Here it
is picked up and removed by microscopic
lymphatic vessels and returned to the
blood. As soon as this fluid enters lymph
capillaries it is know as lymph. Returning
fluid prevents edema and helps maintain
normal blood volume and BP.
• Lymphatic Vessels: unlike blood vessels
these carry fluid away from the tissues.
Lymph capillaries are found in all regions
of the body except bone marrow, CNS,
and tissues like the epidermis which has
no blood vessels. The are composed of
endothelium, in which simple squamous
cells overlap to form a simple one-way
valve. *This valve permits fluid to enter but prevents it
from leaving.
• Lymph capillaries become lymphatic
vessels
• small vessels become lymphatic trunks
which
• merge until lymph fluid enters 2 lymphatic
ducts.
• the right lymphatic duct drains lymph fluid
from the RUQ of the body, and
• thoracic duct drains all of the rest.
• The lymphatic system has no pump, it
depends on pressure gradients to move
the lymph through the vessels. This
pressure comes from the skeletal muscle
action, respiratory movement and the
smooth muscle contraction of the vessel
walls.
• Lymph enters a lymph
node through
• Afferent vessels, filter
through the sinuses,
and leaves the node
through efferent
vessels.
• As mentioned before the 2 ducts that
collect lymph return the fluid to either the
right or left subclavian veins..and it is
plasma again.
• Plasma proteins (synthesized in the liver)
– Prothrombin: clotting
– Fibrinogen: clotting
– Albumin: most abundant: COP(colloid osmotic
pressure) maintains blood volume/BP.
– Globulins: alpha and beta: carriers of molecules like
fats.
– Gamma Globulins: are antibodies produced by
lymphocytes and these initiate the destruction of
pathogens for immunity.
– Plasma also carries heat: by produce of cell
respiration and the production of ATP in cells. From
MA-115
Gamma Globulins
• Refer to page 333 of text; figure 14-1 remember
the antibodies here are plasma proteins.
• Immunoglobulins are also called antibodies (part
of adaptive immunity)
• Antibodies do not kill pathogens they mark them
for destruction and each one is specific for only
one antigen.
• So the antibody-antigen attachment is called the
antibody-antigen complex.
• Now the invader is marked for
phagocytosis by either a neutrophil or a
mature monocyte or macrophage.
• Also at this time a process known as
complement fixation takes place.
– Fixation can be complete or partial
• For bacteria the fixation is called complete and the
antigen will be dead because of the bacteria’s
cellular make up
• In viruses the fixation is said to be partial
because only some of its proteins bond to the
antigen, still it is marked for destruction by a
chemical action called chemotaxis.
• See box 14-3 pg 334 tests that can be done to
help in establishing whether the immune system
has seen a particular antigen and if it has
whether the level of antibodies is high enough to
protect from the pathogen causing the patients
problem.
Other organs of the lymphatic
system
Tonsils
Spleen
Thymus
Tonsils
• These are groups of lymphatic nodules
within a mucous membrane. 3 sets of 2
tonsils that are located in a ring around the
oral cavity.
– Pharyngeal (adenoid) are located at the
posterior wall of the nasopharynx by the
entrance to the eustachian tube
– Palatine (what we call tonsils) are located in
the tonsillar fossae slightly posterior, and
lateral to the uvula, anterior to the oropharynx.
– Lingual tonsils are located at the base of the
tongue, and are occasionally removed during
a tonsillectomy.
– Designed to protect from pathogens entering
via the nose, mouth, and ears. And there are
large amounts of cervical lymph nodes to deal
with them and protect the structures in that
area.
Spleen
• Located in the ULQ of the abdominal
cavity, inferior to the diaphragm and
posterior to the stomach. Protected by the
rib cage.
• Function:
– In a fetus it produces rbcs
– After that it functions like a large lymph node,
however blood flows through it not lymph
fluid.
• In addition the spleen contains plasma cells that produce
antibodies to foreign invaders
• Contains fixed macrophages that phagocytize
pathogens, old rbcs (life span 120 days) and form
bilirubin for portal circulation and then send it to the liver
to be excreted in bile.
• It also stores platelets and destroys them when they are
no longer useful.
• ** not considered a vital organ because we can live
without it, other organs will take up the functions that it
does but a person without a spleen is somewhat
immunocompromized and more susceptible to various
bacterial infections.
Thymus
• Located inferior to the thyroid gland, which is
located in the neck, on both sides of the trachea,
inferior to the larynx. The thyroid gland is part of
the Endocrine system
– Large in the fetus but by age 2 when the immune
system is more mature it begins to shrink and is quite
tiny in adults.
• Function is to take stem cells and produce the T-cells to
establish the immune system, with lymphocytes. Time is
needed to do this, and this is why some vaccines are not give
until the system is established enough that it can make
antibodies when introduced to a antigen. Given too soon, the
young child may not be able to fully develop enough to be
protective.