the immune system
The immune system is the body’s defence against bacteria, viruses and harmful organisms. It’s a very complicated system and there are 3 parts to it:
- skin and mucosal membranes
- antibodies
- blood and lymph cells
skin and mucosal membranes
Mucosal membranes are the lining of the body’s cavities that open to the outside (like your mouth). These, along with your skin, are barriers that protect against harmful organisms.
Cells in the lining of the body cavities produce fluids (like saliva in the digestive system and mucus in the lungs) which act as a defence against bacteria. The body has its own natural, ‘friendly’ bacteria which prevent harmful organisms from taking over.
antibodies
Antibodies are proteins that are made by the body and live in the body’s secretions and fluids. If organisms do manage to enter the body, these antibodies attack them.
blood and lymph cells
These special cells, known as white blood cells, are produced by the lymphatic system, which is made up of:
- bone marrow - the spongy material in the middle of some of our bones
- the thymus gland - a gland in your throat that makes some of the white blood cells
- the spleen - an organ that responds to infections by making white blood cells and antibodies
- lymph nodes throughout the body that are connected by a network of tiny lymphatic vessels
White blood cells play a part in killing any organisms that manage to enter the body. There are many different types and they arrive at the site of damage or infection and destroy the invading organisms.
