|
Tonsils
Tonsils are the two masses on the back
of the throat.
Tonsils and adenoids are near the
entrance to the breathing passages where
they can catch incoming germs, which
cause infections.
|
Adenoids
Adenoids are high in the throat behind
the nose and the roof of the mouth (soft
palate) and are not visible through the
mouth without special instruments.
|
Spleen
A spongy, soft organ about as big as a
person's fist, is located in the upper
left part of the abdomen, just under the
rib cage. The splenic artery brings
blood to the spleen from the heart.
Blood leaves the spleen and moves to the
liver. |
Appendix
The appendix looks somewhat similar to
the tonsils in that it has crypts
penetrating from the gut opening deep
into the tissue and around these are
numerous lymphoid follicles.
|
Peyer's Patches
Lymphoid follicles similar to lymph
nodes or the tonsils, located especially
in the lower small intestine. They
contain white blood cells, defend
against invading bacteria and try to
prevent inadequately digested food
particles from crossing the gut wall and
entering the blood. |
Thymus
In the
thymus gland lymphoid cells undergo a
process of maturation and education
prior to release into the circulation.
This process allows T cells to develop
the important attribute known as self
tolerance.
|
Lymph Nodes
Lymph nodes are small bean shaped
structures lying along the course of
lymphatics. They are aggregated in
particular sites such as the neck,
axillae, groins and para-aortic region.
Knowledge of the sites of lymph nodes is
important in physical examination of
patients. Lymph nodes have two main
functions: 1. phagocytic cells act as
filters for particulate matter and
micro-organisms 2. antigen is presented
to the immune system |
Bone Marrow
All the cells of the immune system are
derived from stem cells in the bone
marrow. The bone marrow is the site of
origin of red blood cells, white cells
(including lymphocytes and macrophages)
and platelets. |
|
The spleen is made up of the white pulp
and the red pulp, each with different
functions. The white pulp is part of the
infection-fighting (immune) system. It
produces white blood cells called
lymphocytes, which in turn produce
antibodies (specialized proteins that
protect against invasion by a foreign
substance). The red pulp filters the
blood, removing unwanted material. The
red pulp contains other white blood
cells called phagocytes that ingest
microorganisms, such as bacteria, fungi,
and viruses. It also monitors red blood
cells, destroying those that are
abnormal or too old or damaged to
function properly. In addition, the red
pulp serves as a reservoir for different
elements of the blood, especially white
blood cells and platelets (cell-like
particles involved in clotting).
However, releasing these elements is a
minor function of the red pulp. |
