The IMMUNE SYSTEM defends our body

Lesson 3.2

We are in constant contact with foreign substances “nonself”.

These substances are called disease-causing agents or pathogens

Pathogens include viruses, fungi, bacteria or parasites.

VIRUSES

BACTERIA

FUNGUS

PARASITES

How can our body protect it’s self from invaders ???

Primary body barrier

Our body in the first place prevent the entry of these pathogens by :

1- Integumentary system defense: 2- Respiratory system defense

3 - digestive system defense

Integumentary system

Consists of: 1- skin : it’s the barrier between the

inside and outside of the body. 2- tears : wash the eyes and hold up

materials that slow down the growth of pathogens.

3- sweat: its acidic, bad medium for pathogens

4-bacteria: found on our skin kill some pathogens

Respiratory system

Including: 1-sneezing and coughing releases

pathogens outside. 2-Cilia: hair-like protrusions in nose and

lungs, which traps dust. 3- mucus: is a thick slippery substance

in nose, throat, lungs. Pathogens stick on this material till the body gets rid of it.

1- mucus trapped dust is released.2-Cilia lining .

Digestive system

Includes 1- saliva in our mouth 2- High acidity in our stomach 3-Liver and pancreatic enzymes 4-mucus along the lining ; works in

trapping. Mucus is also found in our urogenital

tract.

MUCUS membrane in digestive tract.

IF the first body barrier get past and now pathogens are inside the body’s circulatory system, the body then uses it’s Immune system respond.

This respond is done by a group of immune cells and organs.

Immune system organs

1- Bone marrow: produces WBC 2-Thymus: mature WBC 3- Spleen: battle site 4- lymph nodes + lymphatic vessels.

Immune system cells

1- are specialized white blood cells WBC are divided in to:• B cells ─≥ plasma ─≥ produces antibody.• T cells: a- T helper which induce other cells to

work b- T killer which directly destroy an infected

cell.c- Phagocytes: or antigen presenting cells, they

phagocyte or eat pathogen and present it’s particles on it’s surface .

d- mast cells release histamine,

Activated B cells will divide in to plasma and memory cells.

How B cell is activated:

B cell releasing antibodies

Antibodies: Y shaped molecule having a specific binding site.

T killer cells kill cells by inserting chemicals to the infected cell.

Phagocytes: eat antigen .digest it and present its small particle on the top of its membrane.

During an immune response WBC increase in number. Immune cells circulate in the circulatory and lymphatic system but mainly in the lymphatic system.

Lymphatic system

It transports lymph: containing pathogen fighting WBC, lymph moves through the lymphatic vessels (like veins) to the damaged tissue.

Lymph drift through lymphatic vessels when our skeletal muscles contract (or when we move), it has no pump system.

Lymphatic vessels connect lymph nodes

Lymph moves through lymph nodes which filters out pathogens and store WBC + antibodies that’s why when your sick your nodes swell.

Immune response

There is two types of immune response:

1- specific : its against specific antigen ; and its permanent

2 – Nonspecific response: like inflammation and allergy; its against any foreign body. It is temporary.

Nonspecific immune response

Inflammation: it’s the bodies first defense against injuries and infection

Symptoms: swelling,redness,and heat. When tissue is irritated or damaged,

histamine is released causing a raise in temperature and increase blood flow to the area, thereby allowing more RBC,WBC and antibodies to reach quicker.

High temperature increase the speed of WBC and weakens pathogens.

If many tissues are affected; histamine will be every where, as a consequence the whole body temp will rise above 37 which we call FEVER

This temperature must be lowered or it will cause tissue damage.

Medicine is advisable

Inflammation: case of injury

Inflammation: wasp sting

Specific immune response

The body first detects a foreign antigen..

It performs a specific immune response This response provide protection from

future exposure to this antigen.

When the body recognizes a foreign antigen ,B and T cells divide rapidly in huge numbers but not all of them fight the battle but some are kept as memory cells for future exposure to the same antigen,

So that upon the second entry of the same antigen the body will directly respond in shorter and more effective way.

Antibodies hold tight the antigen marking it for T killers, chemicals or other immune cells to get rid of it

Antibody binds antigens, neutralizing them.

Summary

Immunity:

Is the resistance to sickness. It is accomplished through the memory

B cells which are kept in your body .These B cells already recognized the

pathogen during its first entrance so now its ready to release antibody directly and destroy this pathogen, so that we don’t even get ill.

Immunity: is the resistance to sickness

Immunity could be: 1- active: its when your body makes its

own antibody. It will be ready for the next exposure to the same pathogen.

2-passive: antibodies are not produced by the body itself but are transmit or delivered to the person. Example when the mother breastfeed her child.

Treatment and prevention

Our body takes time to develop a defense against certain pathogen.. So the disease will be able to cause significant and lasting damage before it is defeated.

Other pathogens are so strong that immune system cant respond. Medication is suitable in this case.

Prevention method:

VACCINATION: it’s a way to develop immunity using vaccine.

Vaccine is an injection of a dead or weekend pathogen which upon injection it stimulates our immune response to produce antibodies while we stay healthy.

Vaccination protects babies and adults from their grandparents ilness.It could be taken by mouth or as an injection.

Treatment

It could be used to decrease the symptoms of a disease or prevent further damage of tissue but cant defend the pathogen.

Medicines are effective to destroy pathogen: example :antibiotics: are medicines that block the growth and reproduction of bacteria.

We use them in case of step throat or ear infection.

Other medicines are used to cure diseases coming from viruses, fungi or parasites.

Never forget your baby vaccination.