Second lines of Defense

If microbes get past your first line of defence, it is up to the second line of defence, your immune system, to keep you from getting sick. It is made up of lots of different cells that are always patrolling your body and fighting any bad microbes they find :

• Phagocytes - cells which "eat" foreign material to destroy them :
• Nutrinophils - phagocytize bacteria
• Eosinophyls - secrete enzymes to kill parasitic worms
• Basophils - secrete histamine to enhance inflammation
• Macrophages - "big eaters" phagocytize just about anything

These highly specialized white blood cells surround, engulf and destroy antigens that could compromise your body’s health.

Your body is exposed to many different types of microbes everyday, so your immune system is always hard at work, keeping you healthy!

image's source : The Immune System : (http://www.uic.edu/classes/bios/bios100/summer2002/lect18.htm)

Response's Steps of Immune System

1- Recognition : White blood cell surrounds pathogen and signals T cells. More T cells are produced and helper T cells signal B cells

2- Mobilization: B cells produce antibodies

3- Disposal: antibodies destroy pathogens

4- Immunity : some antibodies remain for future use

How diseases are spread ??

Image source : Science aid.co.uk ( scienceaid.co.uk/biology/micro/immune.html)

Specific Immnunity

When your non-specific immunity fails to kill the pathogen, the specific immunity is called.

Antigens are the foreign molecules that enter into your body, and the antibodies are proteins made in response to a specific antigen.

In the specific immunity, Lymphocyte T cells ( which are leucocytes) respond:

- Killer T cells, release enzymes destroying the invading foreign molecules.

- Helper T cells , stimulate other lymphocytes B cells, to form antibodies.



Antibodies help the body to build defenses in two ways:

- Active immunity: the body makes his own antibodies in response to an antigen. It can be also achieved by an artificial immunization through vaccination ( giving a vaccine by mouth), so that your body can respond quickly when it later faces the same antigen, because the blood is already containing the antibodies needed.

- Passive immunity : antibodies are produced in another animals and being produced into your body. it doesn't last for long period as the active immunity


What are the 4 steps of a response to disease-causing organisms??

Source of the image :Could You Ever Live Forever : (www.daviddarling.info/childrens_encyclopedia/..)

Source of image: Nephrology (www.cyberounds.com/cmecontent/art394.html‎)

First Lines of Defense

In this section, we are going to talk about the first lines of defense, which are part of the Non-specific immunity: it includes the skin and respiratory, digestive, and circulatory system.

The skin: it prevents pathogens from entering the body, (except for the case of injury). Secretions from the skin are acidic, which prevent the growth of pathogens in this environment.

Respiratory system: it traps the pathogens through cilia and mucus (hairlike structures). The mucus contain enzymes that weaken the pathogen and expel it from the body through coughing or sneezing

Digestive system: it defenses the body through the saliva of the mouth ,enzymes of the stomach , pancreas and liver ,hydrochloric cid in the stomach and mucus on the digestive tract

Circulatory system: contain white blood cell that patrol the body, and digest bacteria invaded. Fever is developed when white blood cells don’t destroy the bacteria quickly, because some pathogens are sensitive to temperature that slows their growth and activity and speed up body defense.

What will happen if the pathogens get past these first-line defenses???

Souce of image: Human Diseases and Conditions (http://www.humanillnesses.com/General-Information-and-Infectious-Diseases-A-Co/Body-Defenses.html)

Welcome!

Welcome to the Immunity system and Disease blog. This blog is offered to Grade 8 students. We will use it to share information and post announcements.

hope it will be useful for you as well as enjoyable :)

source of image : Connections ( coconnections.wonecks.net/page/2/)

Note:

This blog provides you the basic information that you should know concerning the immune system. However, reading your book is a must.

Required book:

Life Science: Human Body Systems, Book D / National Geographic- The McGraw.Hill Companies