The immune system is a complex system of organs, cells and proteins that primarily defends the body against infections.
Major organs of the Immune System:
Bone marrow The bone marrow is a soft jello-like tissue found inside the bones. The cells of the immune system are created in the bone marrow from stem cells.
Thymus The thymus is a major gland located in the middle of the chest between the lungs.
A certain type of white blood cells (T Lymphocytes) mature in the thymus.
It is resposnible for keeping the immune system working properly.
It prevents human autoimmune diseases through induction of apoptosis to autoreactive T cells. Any disturbance in this process can lead to the escape of autoreactive T cells that may trigger an autoimmune disease.
It’s constantly growing in size and reaches its peak during childhood. After puberty is gradually shrinks and becomes less active.
Lymph nodes Lymph nodes are tissues full of immune cells. They are located strategically everywhere throughout the body. Some are in the neck, the armpit, the genital region, digestive tract etc. They are connected with each other through a large network of blood and lymphatic vessels.
Spleen It contains a large number of immune system cells.
About 25 percent of the blood that comes from the heart flows through the spleen on every beat
As blood circulates through the spleen, it is filtered to detect pathogens.
If pathogens are detected, immune system cells are activated and increase in number.
Skin Skin serves as an important physical barrier from many of the disease-causing agents that we come into contact with on a daily basis.
The immune system is divided into two lines of defence:
The Innate Immune System The Adaptive Immune System
The first line of defence. When a pathogens enters the body, certain cells can quickly respond. The second line of defence. Certain cells create special proteins to destroy a specific pathogen. It is more effective and can create long lasting immunity.
Physical barriers
The skin is an important protective barrier.
Openings into our bodies like nose, mouth, respiratory, digestive, and genital tracts have additional protective features:
Mucus coating
Cilia and nasal hairs
Responses like sneezing, watery eyes, vomiting, diarrhea, and fever
Chemical barriers
Mucus contains lysozymes
Stomach acid (HCl)
The white blood cells (leukocytes) are divided into:
Granulocytes:
Neutrophils: Most common, phagocytic, fight bacteria.