External defense systems, which include your skin, tears, mucus, saliva, stomach acid, cilia and helpful bacteria. Internal defense
systems, which include white blood cells and the antibodies they produce.
White Blood cells that protect your body
Neutrophils are phagocytes, cells that consume invading pathogens. Lymphocytes, the second most common type of
white blood cell, disseminate through the organs and tissues of the lymphatic system. Lymphocytes target specific
pathogens as part of the immune response.
Immune Deficiencies
Primary immune deficiencies, with which people are born; acquired immune deficiencies, which include diabetes,
HIV, and certain blood disorders, and autoimmune disease, which results from an overactive, inappropriately
functioning immune system.
3 types of immunity
Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection. Adaptive immunity: Adaptive (or active)
immunity develops throughout our lives. Passive immunity: Passive immunity is "borrowed" from another source and it lasts for a short
time.
Organs
The key primary lymphoid organs of the immune system include the thymus
and bone marrow, as well as secondary lymphatic tissues including spleen,
tonsils, lymph vessels, lymph nodes, adenoids, skin, and liver.
Functions
Thymus
a small organ in your upper chest, behind the breastbone, where lymphocytes called T cells grow and mature
during childhood. When you reach adulthood, your mature T cells can divide to make new T cells.
Bone marrow
the soft tissue inside your bones where all blood cells, including lymphocytes, are made. Bone marrow produces T
cells and other lymphocytes called B cells.
Spleen
a fist-sized organ at the upper left of the abdomen, just behind the stomach. The spleen contains white blood
cells that respond to any antigens collected from the blood.
Lymphoid tissue “clumps”
You also have areas of lymphoid tissue throughout the body. Their job is to trap antigens and present them to
lymphocytes to trigger an immune response. Lymphoid tissues along the gastrointestinal tract include the
tonsils and adenoids, which are located behind the throat and nose, and the appendix, a small organ attached to
the large intestine. You also have areas of lymphoid tissue along your respiratory system.
Lymph vessels
pick up wastes such as protein, cellular debris, bacteria, and viruses that leak out of the body’s blood vessels. This
waste-containing fluid is called lymph, and it travels through the lymph vessels into the lymph nodes. You have
lymph vessels throughout your body, in much the same way that you have blood vessels (arteries and veins).
Lymph nodes
are small, round organs that filter out bacteria, waste, and other toxins and also contain infection-fighting white
blood cells. The nodes play a key role in recognizing and destroying these substances while also signaling the
body to launch an immune response. You have clusters of lymph nodes in your groin, under your arms, and in
your neck, as well as more nodes located along other lymphatic pathways in the chest, abdomen, and pelvis.
Why is the immune system so important?
The main purpose of your immune system is to protect your body from viruses and bacteria. ... Your immune system works by
recognising the difference between your body's cells and alien cells, allowing it to destroy any that could be potentially harmful.
Where is your immune system located
The immune system is made up of organs that control the production and maturation of certain defense cells, the lymphocytes. Bone
marrow and the thymus, a gland situated above the heart and behind the breast bone, are so-called primary lymphoid organs. The bone
marrow produces defense cells.
What do vaccines do to the immune system?
A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this,
certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are
called antigens, and they are present on all viruses and bacteria.