Spleen -- The spleen is an immunologic filter of the blood. It is
made up of B cells, T cells, macrophages, dendritic cells, natural
killer cells and red blood cells. In addition to capturing foreign
materials (antigens) from the blood that passes through the spleen,
migratory macrophages and dendritic cells bring antigens to the
spleen via the bloodstream. An immune response is initiated when the
macrophage or dendritic cells present the antigen to the appropriate
B or T cells. This organ can be thought of as an immunological
conference center. In the spleen, B cells become activated and
produce large amounts of antibody. Also, old red blood cells are
destroyed in the spleen.

WHERE IS IT LOCATED ?

Shaped much like a loose fist and tucked under the left side of the
diaphragm, the spleen is the most ignored and misunderstood of all
organs. After all, we read numerous times that someone in an
automobile accident or a fight has a ruptured spleen so the spleen
is removed (splenectomy) and life goes on.

The spleen is formed by reticular and lymphatic tissue and is the
largest lymph organ. The spleen lies in the left hypochondriac
region of the abdominal cavity between the fundus of the stomach and
the diaphragm. It is purplish in colour and varies in size in
different individuals, but it is usually about 120mm (4.75 inches)
long, 70mm wide (2.75 inches) and 25 mm (1 inch) thick. It weighs
about 0.2 Kg (just under half a pound).

SEE PHOTOS click here

http://photos.groups.yahoo.com/group/healingyu/vwp?.dir=/IMMUNE+SYSTE
M&.src=gr&.dnm=spleen.jpg&.view=t&.done=http%
3a//photos.groups.yahoo.com/group/healingyu/lst%3f%26.dir=/IMMUNE%
2bSYSTEM%26.src=gr%26.view=t


Functions


There are three major functions of the spleen and these are handled
by three different tissues within the spleen.

1.Reticuloendothelial tissue - concerned with phagocytosis of
erythrocytes and cell debris from the blood stream. This same tissue
may produce foci of haemopoiesis when RBC's are needed.

2.Venous sinusoids along with the power of the spleen to contract,
provides a method for expelling the contained blood to meet
increased circulatory demands in certain animals.

3.White pulp provides lymphocytes and a source of plasma cells and
hence antibodies for the cellular and humoral specific immune
defenses.


Normal Physiology
Lymph drains into open-ended, one-way lymph capillaries. It moves
more slowly than blood, pushed along mainly by a person's breathing
and contractions of the skeletal muscles. The walls of blood
capillaries are very thin, and they have many tiny openings to allow
gases, water, and chemicals to pass through to nourish cells and to
take away waste products. Interstitial fluid passes out of these
openings to bathe the body tissues.

Lymph vessels recycle the interstitial fluid and return it to the
bloodstream in the circulatory system. They collect the fluid and
carry it from all of the body's tissues and then empty it into large
veins in the upper chest, near the neck.

Lymph nodes are made of a meshlike network of tissue. Lymph enters
the lymph node and works its way through passages called sinuses.
The nodes contain macrophages, phagocytic cells that engulf
(phagocytize) and destroy bacteria, dead tissue, and other foreign
matter, removing them from the bloodstream. After these substances
have been filtered out, the lymph then leaves the nodes and returns
to the veins, where it re-enters the bloodstream.

When a person has an infection, germs collect in great numbers in
the lymph nodes. If the throat is infected, for example, the lymph
nodes of the neck may swell. Sometimes the phagocytic cells may not
be able to destroy all of the germs, and a local infection in the
nodes may result.

Because the lymphatic system extends to the far reaches of the body,
it also plays a role in the spread of cancer. This is why lymph
nodes near a cancerous growth are usually removed with the growth.




Clinical Considerations

Surgical removal of the spleen may be carried out in healthy
patients whose spleen has been ruptured by trauma. In the long run,
splenectomy has no dire effects .

There is an increased risk of infection after splenectomy,
especially in very young children.

In hypertrophic spleen due to overactivity of its macrophage system,
it can be removed without apparent ill effects.



Diseases, Conditions, Disorders, and Dysfunctions
Because the lymphatic system branches through most of the parts of
the body, it may be involved in a wide range of conditions. Diseases
may affect the lymph nodes, the spleen, or the collections of
lymphoid tissue that occur in certain areas of the body.

Disorders of the lymph nodes

Lymphadenopathy. Most lymph nodes in the body can't be felt easily
unless they become swollen or enlarged. Lymphadenopathy is an
increase in the size of a lymph node or nodes, most often as the
result of a nearby infection (for example, lymphadenopathy in the
neck might be the result of an infection of the throat). Less
commonly (particularly in children), swelling of the lymph nodes can
be due to an infiltration of cancerous cells. If lymphadenopathy is
generalized (meaning that the swelling is present in several lymph
node groups throughout the body), it usually indicates that the
person has a systemic disease.
Lymphadenitis, or adenitis, is an inflammation (swelling,
tenderness, and sometimes redness and warmth of the overlying skin)
of the lymph node due to an infection of the tissue in the node
itself. In children, this condition most commonly involves the lymph
nodes of the neck.
Lymphomas. A group of cancers that arise from the lymph nodes, these
diseases result when lymphocytes undergo changes and start to
multiply out of control. The involved lymph nodes enlarge, and the
cancer cells crowd out healthy cells and may form tumors (solid
growths) in other parts of the body.

Disorders of the spleen

Splenomegaly (enlarged spleen). In children, the spleen is usually
small enough that it can't be felt by pressing on the abdomen, but
the spleen can enlarge to several times its normal size with certain
diseases. There are many possible reasons for this including various
blood diseases and cancers, but the most common cause in children is
infection (particularly viral infections). Infectious mononucleosis,
a condition usually caused by the Epstein-Barr virus (EBV), is one
of many viral infections associated with an enlarged spleen.
Children and teens with an enlarged spleen should avoid contact
sports because they can have a life-threatening loss of blood if
their spleen is ruptured.

Disorders of other lymphoid tissue

Tonsillitis. An extremely common condition, particularly in
children, tonsillitis occurs when the tonsils, the collections of
lymphoid tissue in the back of the mouth at the top of the throat,
are involved in a bacterial or viral infection that causes them to
become swollen and inflamed. The tonsils normally help to filter out
bacteria and other microorganisms to aid the body in fighting
infection. Symptoms include sore throat, high fever, and difficulty
swallowing. The infection may also spread to the throat and
surrounding areas, causing pain and inflammation (pharyngitis).


That is why this organ is a vital part of our defense. Take good
care of it!

Maria