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Components of Blood


 Blood is a tissue.An adult has a blood volume of approximately 5 liters.  
•Blood is the only tissue that exists in both the liquid and solid state simultaneously.

Functions of blood:

•Delivers digested nutrients to cells
•Delivers oxygen to cells
•Delivers enzymes, hormones and other chemical messengers to cells
•Delivers water, vitamins and minerals to cells

•Picks up carbon dioxide from cells and carries it to the lungs to be expelled
•Picks up urea and other chemical wastes and carries them to the liver and kidneys for disposal:
•Picks up excess body heat and brings it to the skin to be excreted

Fights disease
•Helps begin the repair process after a cut or other injury

Parts of Human Blood

Plasma: The non-living, liquid part of blood
•Yellow in color
•Plasma is composed of about 92% water and 8% proteins, salts and other various chemicals
•Plasma makes up about 45 - 50% of blood's volume

Red blood cells (RBC's):  
Cells in blood that carry oxygen
•Most common type of blood cell (5 000 000/drop of blood) 
•Also called red corpuscles or erythrocytes
•Small in size
•Give blood its color
•Are round and biconvex in shape (thin in the middle and thick around the edges)
•Mature RBC's are found in the blood vessels.  They have no nucleus.
•Have a life span of about 120 days (4 months)
•Contains hemoglobin:  a protein that bonds with oxygen.  It allows RBC's to carry oxygen
•Contains iron
White blood cells (WBC's):  
Destroy harmful viruses and bacteria (pathogens) and help remove dead pathogens and body cells from the body.
•Also called white corpuscles or leukocytes
•Have a nucleus
•Larger than RBC's
•Life span about 10 days
•About 8000 WBC's/drop of blood
•Can move through the walls of blood vessels into the lymphatic system.  RBC's must stay inside   the blood vessels
•Numbers increase rapidly in the presence of a pathogen (can go from 8000/drop to over 30 000/drop in a matter of hours)
•Number returns to normal when the infection is cleared from the body
Infection:  an attack on the body's cells by a pathogen

Pus:A whitish substance made of millions of  dead WBC's and living and dead bacteria

•Pus usually forms when the pathogen is winning the battle

WBC's rid the body of pathogens in the process of phagocytosis:  the WBC surrounds, engulfs and "eats" the invading pathogen.

Cell fragments that aid in the formation of blood clots.
•Have no nucleus
•Smaller than RBC's
•25 000/drop of blood
•Life span is 5 - 10 days
•Made in the red marrow
•Formerly believed to be fragments of RBC's, it is now believed that platelets are specially made by the bone marrow to aid in blood clotting

Blood clot:Dried blood that has formed a plug over a wound to slow and eventually stop bleeding.

Formation of a Blood Clot:

1.When an injury occurs, platelets are ruptured.
2.Ruptured platelets release a protein called thromboplastin.
3.Thromboplastin reacts with calcium and another protein (in the plasma) called prothrombin.The result of this reaction is a new protein called thrombin.
4.Thrombin then reacts with another protein found in the blood plasma called Fibrinogen.The result of this reaction is another new protein.  This one is called Fibrin.
5.Fibrin forms long, thin strands that form a net over the wound.RBC's become trapped in this net, and because they are exposed to air, they dry out.The dried,RBC's first form a clot, then dry into a scab that prevents further blood loss.

Blood Types:

There four different blood types in the human population.
•The blood types are different because of proteins found both on the surface of the RBC's (antigens) and in the plasma (antibodies)
•Antigens and antibodies of the same type will bond with each other.  This causes the blood to thicken and become gelatinous in the blood vessels. This process is called agglutination.
•Antigens and antibodies of different types will not react with each other, because their shapes are different.

Note:Type AB has both types of antigens on its RBC's, but does not have the capability to produce antibodies of either type, no matter what antigen is present.  This inability to produce antibodies makes Type AB the universal recipient.  A person with Type AB blood can receive any blood type, however, they would respond best to Type AB blood.

Note:Type O does not have any antigens on the surface of its RBC's, but it can produce antibodies to bond with either the Type A or the Type B antigen, should either be introduced into the body.  Because Type O can produce antibodies to both antigens, Type O  blood can only be mixed with Type O blood, but since Type O RBC's carry no antigens on their surface, they can be mixed with any other blood type with no risk of agglutination.  This makes Type O the universal donor.

Rh Factor: 
 Another kind of protein found on the surface of RBC's
•If the protein is present, the person is classified as positive (+)
•If the protein is not present, the person is classified as negative (-)

A Rh(-) person will form antibodies to attack and destroy the Rh protein if the person is exposed to the Rh protein (Rh(+) blood)