October 15, 2002

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Red Blood Cells, colorized, Credit: MicroAngela You probably have seen blood sometime in your life.
 Were you curious about why you had it,
 where it came from or  why it  was red? 
Question Marks
 This is the place to find your answers.

PhotoCredit: MicroAngela               Let's start our journey about blood with...

What is blood and what does blood do for you?
          Blood is a fluid made up of cells and a watery part. It supplies all parts of your body with the oxygen and nutrients you need to stay alive. Blood carries away your body's wastes such as carbon dioxide. Blood protects you from germs that can cause disease. Blood can warm you up or cool you down and help heal wounds.

What is in blood? Let's look at several types of blood cells and the watery part of your blood. Each has an important job to do.
Red blood cells

Concave shaped red blood cells. Credit:Nanaworld,
Photo credit: NANOWORLD
White blood cells

A white blood cell scanning electron micrograph. Credit:Nanaworld,
Photo credit: NANOWORLD

The arrow points to a platelet. Credit:Nanaworld,
Photo credit: NANOWORLD

Plasma is a pale-gold color
More information...
Job and other facts
% of blood
Live for:

Red Blood Cells

also called erythrocytes
carry oxygen to cells
carry carbon dioxide to the lungs
make blood red,
concave shape, about 5,000,000 in a speck of blood
45% of your blood
100-120 days

White Blood Cells
also called leukocyte

fight infections,
break down dead cells
colorless, irregular shape, can change shape,
larger than red blood cells, about 10,000 in a speck of blood
less than 1% of your blood
most up to 3 days

also called thrombocytes

help blood to clot, or thicken (Photo) disk shape,
smaller than red blood cells, about 250,000 in a speck of blood
about 5% of your blood
7-10 days
watery part
carries red blood cells, white blood cells, platelets, and other necessary things for your body mostly water,
but also sugars, salts, nutrients, proteins, minerals, wastes vitamins, hormones, and fats.
more than 50% of your blood

To learn more, Red Gold: The Epic Story of Blood from PBS and WNET
will take you on a blood journey
that you shouldn't miss!!
How does blood move throughout your body?
           Your body has a network of tubes, called blood vessels, through which blood flows. The names of these blood vessels are: arteries, veins, and capillaries. Blood constantly flows from your heart, around your body and back to your heart through these vessels. The heart has a very important job! Here are the details.

Clipart of a HeartThe heart is a big muscle about the size of your fist. Its job is to pump blood to all parts of the body. The heart beats 70 -80 times a minute and it beats more than thirty million times a year! It never stops! The heart has four chambers (like rooms); two atria, and two ventricles. Your heart, blood, and blood vessels all work together. This is called the circulatory system. Find out more about two kinds of circulation (systemic circulation and pulmonary circulation) by viewing this ANIMATION.

What is your pulse? Doctor taking a pulse clipart
           Your arteries expand and contract when the lower chambers of the heart, the ventricles, contract. You can feel this throbbing at a few places on your body where the arteries are close to the skin. This is called your pulse.
Now try this activity: Seeing your Pulse.

SphygmomanometerWhat is your blood pressure?
           Your blood pressure is the pressure made by the heart in full contraction, and the pressure made when the contraction stops.
Have fun learning about Blood Pressure , and how to say the name of this sphygmomanometer.

Where is blood made?
           How do you replace red blood cells, white blood cells, and platelets that die? Red blood cells, platelets, and white blood cells are made by special cells in the marrow of our largest bones. Some cells are made in the spleen and lymph glands.

Why is your blood red? The Franklin Institute has the answer.

What is blood donation?         
           Did you know that you can donate blood? Find out about blood donation from The New York Blood Center.
Blood TypesWhat are Blood Types?
In 1902 Karl Landsteiner discovered there are several types of human blood. He called these "A, B, AB, O". This is important to know because the recipient of a blood transfusion must have the same blood type as the donor of the blood. If they don't match - illness or death could result.   Study more about the history & pioneers of blood research at PBS's Red Gold: The Epic Story of Blood.

Do all animals have blood?

          Many invertebrate animals (animals without a backbone), such as coral, jelly fish and flat worms do not have blood because they are able to absorb nutrients and move gases and wastes directly to the outside of their bodies.
Are all hearts the same?

          Fish have a two-chambered heart with one atrium and one ventricle. Frogs have a three-chambered heart with two atria and one ventricle. Humans, all other mammals and all birds have a four-chambered heart with two atria and two ventricles.
Is blood any other color ?
           Blood comes in other colors. Earthworms, leeches, and insects have green blood. 
Starfish and many other invertebrates have clear or yellowish blood. Lobsters and crabs have blue blood because it contains copper instead of iron.               

Cartoon of a man and a heart

What can you do to keep your heart healthy?
          Heart disease is the #1 cause of death in the United States.
Find out what you can do to keep your heart healthy, and have a great life. Get regular exercise, eat a balanced diet, and don't smoke!!!
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