There are 2 main parts of the immune system:
*The innate immune system. People are born with this. The innate immune system is the first line of defense against pathogens.
*The adaptive immune system. People develop this when their body is exposed to microbes or chemicals released by microbes.
The cells of both parts of the immune system are made in different organs of the body, including:
*Adenoids: are part of the lymphatic system. The lymphatic system clears away infection and keeps body fluids in balance.
*Bone marrow: All cells of the immune system are created in the bone marrow from a common type of starting cell, called a stem cell. These stem cells later develop into specific cell types, including red blood cells, platelets (important for blood clotting), and white blood cells (important for immune responses). White blood cells are the key players in human immune system. They are made in human bone marrow and are part of the lymphatic system.
*Lymph nodes: Primary lymphoid organs organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes. Secondary lymphoid organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body. It is in these organs where the cells of the immune system do their job of fighting off germs and foreign substances.
*Lymphatic vessels: lymph vessels carry fluid (rich in immune system cells and signaling chemicals) toward the heart.
*Peyer patches: are a series of small lymphoid organs situated in the wall of the small intestine. The function of Peyer’s patches is to analyze and respond to pathogenic microbes in the ileum.
*Spleen: The spleen is a blood-filtering organ that removes microbes and destroys old or damaged red blood cells.
*Thymus: The thymus filters and monitors human blood content. It produces the white blood cells called T-lymphocytes.
*Tonsils: It is secondary lymphoid organ.
Immune system in human body
