The immune system & Body defences
The immune system consists of organs, cells, and substances that work together to fight
infection (microbes). White blood cells, antibodies, the complement system, the lymphatic
system, the spleen, the thymus, and the bone marrow are the key components of the immune
system. These are the immune system components that actively combat infection.
Microbial infection and the immune system
Memory cells are white blood cells (B- and T-lymphocytes) that keep track of every germ the
immune system has ever fought. This means that if the microbe re-enters the body, it will be
recognised and destroyed immediately, before it can multiply and make you sick.
Some infections, like the flu and the common cold, have to be fought many times because
so many different viruses or strains of the same type of virus can cause these illnesses.
Catching a cold or flu from one virus does not give you immunity against the others.
The main parts of the immune system are:
- White blood cells scour the blood and tissues of your body for foreign invaders
(microbes) such bacteria, viruses, parasites, and fungus. They launch an immune
attack when they find them.
- Lymphocytes (such as B-cells, T-cells, and natural killer cells) and a variety of other
immune cells make up white blood cells.
- Antibodies are proteins that bind to each other.
Antibodies aid the body in combating microorganisms and the toxins (poisons) that
they create. They accomplish this by recognising antigens on the organism's surface
or in the molecules it produces, which identify the microbe or toxin as foreign. These
antigens are then marked for destruction by the antibodies. This attack involves a
large number of cells, proteins, and chemicals.
- System of complements
The complement system is made up of proteins that help antibodies execute their job
better.
- The lymphatic system transports fluid around the body
The lymphatic system is a delicate tube network that runs throughout the body. The
lymphatic system's main functions are to: regulate body fluid levels, respond to
, pathogens, and deal with cancer cells and cell products that would otherwise cause
sickness or diseases. The intestine absorbs part of the lipids in our diet. Lymph
nodes which trap bacteria lymph vessels — tubes that convey lymph, the colourless
fluid that bathes and traps illness in your body's tissues
white blood cells that fight infection white blood cells that fight infection (lymphocytes)
Spleen
The spleen is a blood-filtering organ that filters out germs and kills damaged or old
red blood cells. It also produces immune system components that combat sickness
(including antibodies and lymphocytes).
Bone marrow
The spongy tissue located inside your bones is called bone marrow. It makes the red
blood cells that carry oxygen throughout our bodies, the white blood cells that fight
infection, and the platelets that help our blood clot.
Thymus
The thymus filters and monitors the contents of your blood. T-lymphocytes are white
blood cells produced by this organ.
Other microbe-fighting mechanisms in the body
In addition to the immune system, the body has various different mechanisms for fighting
microorganisms, including:
The skin is a water-resistant barrier that secretes oil containing microorganisms.
-death characteristics
lungs - phlegm catches foreign particles in the lungs, and little hairs (cilia) wave the mucus
upwards so it may be spat up digestive tract - the mucous lining carries antibodies, and
stomach acid can destroy most microorganisms
Anti-bacterial enzymes are found in human fluids such as skin oil, saliva, and tears, which
help to minimise the chance of infection. Constant bowel and urinary tract flushing are also
beneficial.
Fever is also a type of immunological reaction.
Some infections cause a rise in body temperature, sometimes known as a fever. This is a
reaction of the immune system. Some microorganisms can be killed by a rise in temperature.
The body's mending mechanism is also triggered by fever.
The two types of The immune system
the immune system is often split into two categories: innate and adaptive.
Innate immunity
Immunity that is innate
Nonspecific defensive mechanisms that kick in immediately or within hours of an antigen's
presence in the body are referred to as innate immunity. Physical barriers, such as skin,
chemicals in the circulation, and immune system cells that target foreign cells in the body are
examples of these systems. Chemical characteristics of the antigen trigger the innate
immune response.
Adaptive immunity
Antigen-specific immune response is referred to as adaptive immunity. The adaptive immune
response is more sophisticated than the innate immune response. First, the antigen must be
processed and identified. The adaptive immune system develops an army of immune cells
