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Blood and the Immune System
body systems       circulatory system respiratory system digestive system nervous system blood & immune system endocrine system muscular system skeletal system excretory system reproductive system

 

BLOOD TYPES

A, B, AB and O blood types are determined by the presence or absence of antigens (specific chemicals) on the red blood cells

Negative (-) or positive (+) blood types are determined by whether or not a chemical called the Rh factor is present on the red blood cells. If someone has this chemical on his red blood cells, then his blood type is positive (+), if he doesn't, then his blood type is negative (-)

Blood contains four major parts:

  • Red blood cells - carry oxygen (O2) from your lungs to your body cells and carbon dioxide (CO2) from your body cells back to your lungs to be exhaled
  • Platelets - help clot blood
  • White blood cells - fight germs that infect the body
  • Plasma - a yellowish liquid that consists mostly of water

Immune System:

The body's immune system includes several kinds of white cells in blood, body fluids, and lymph nodes. These white cells attack any germs that are in the body. The immune system is like an army that proctects you from disease.

  • Your skin is the first wall of protection against foreign invaders that cause disease.
  • The second line of defense are fluids like mucus found in your respiratory system and tears from your eyes.

If the invaders do pass through these defenses there is an army battalion of white blood cells and their weapons that fight the germs:

  • Helper Tcells - act as the "lookout" for your body by recognizing invaders and then send signals to the other white blood cells
  • Bcells - make antibodies to smother the invaders once they receive the signals from the helper Tcells
  • Killer Tcells - kill the invaders once they receive the signals from the helper Tcells
  • Phagocytes - act as "eating" cells. They destroy invaders with chemicals and then eat them.

Cuts and Clots

A wound or cut in the skin leaks blood from the damaged blood vessels (1).
Chemicals released from damaged cells and platelets make dissolved substances in the blood turn into a meshwork of microfibres, of the substance fibrin. This network traps blood cells (2).

Gradually the meshwork hardens into a clump or clot that seals the leak. The clot then hardens and dries further into a protective scab (3).

White cells arrive to attack any germs, and the skin begins to regrow and heal.


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