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Anatomy of the Immune System

The immune system is the parts of the body that work together to identify and destroy a bacteria, virus, or disease. In order for the immune system to function correctly, it must be able to identify these in comparison to the body's own healthy tissue. Learn more about the parts of the immune system by reading below.

1. Bone marrow: a substance found in some of the bones located throughout the human body. Bones that have marrow include the hips and thigh bones. Bone marrow is where the cells of the immune system come from. These include red and white blood cells, as well as platelets.


2. Thymus
: The thymus is where lymphoid cells mature before being released into the body's system. This allows T cells to develop self tolerance.
a) Anatomy: The thymus is located beneath the chest bone. Its purpose is to help the body produce a certain type of white blood cell.
b) Histology: is made of lymphoid tissues, comprised of lymphocytes. It is made up of the cortex and the medulla. Lymphoid cells enter through the cortex where they mature, and then on to the medulla. From the medulla, they enter circulation.


3. Lymph nodes
: Found throughout the body, part of the lymphatic system. Lymph nodes act as filters for the body.

a) Structure: Outside the lymph node, there is a capsule made of fiber. It extends to the inside of the lymph node, where the node is then divided into the cortex and medulla.
b) Cortex: The outer layer of the cortex, consisting mainly of B cells.
c) Paracortex: The inner layer of the cortex, consisting mainly of T cells.
d) Medulla: Consists of medullary cords, medullary sinuses, and large blood cells. These structures are made of B cells, plasma, and histocites.
e) Passage of lymph: lymph passes into the nodes through the afferent lymphatic and then into the marginal sinus. Then it moves though the cortical sinuses to reach the medullary sinuses before exiting through the efferent lymphatic.


4. Spleen
can be found in the upper left area of the abdomen. It works as a filter and as part of the immune system.
a) Structure: The spleen is made of up two different parts, the red pulp, and the white pulp. It has a complex structure of septa to help the body filter out foreign bodies.
b) Red pulp: works to remove old or damaged red blood cells from the body.
c) White pulp: is comprised of various kinds of cells including T cells and B cells. This area helps to fight antigens in the blood.


5. Mucosa-associated lymphoid tissue (MALT)
is located throughout the bodies mucosal linings and is the largest part of the lymphatic tissue. It serves to protect the body from a wide variety of antigens. The naming structure refers to the location of the lymphoid tissue, so other names include:

  • GALT: gut associated lymphoid tissue
  • BALT: bronchial/tracheal-associated lymphoid tissue
  • NALT: nose-associated lymphoid tissue


6. Lymphocyte recirculation

This refers to the cycle which allows lymphocytes to circulate through both lymphoid and non-lymphoid tissues. This helps in ensuring the lymphocytes are exposed to antigens they know so they can help rid the body of them.

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